@comment{{Rajesh Paleti PAPERS}}
@article{Abay201374,
title = {The joint analysis of injury severity of drivers in two-vehicle crashes accommodating seat belt use endogeneity },
journal = {Transportation Research Part B: Methodological },
volume = {50},
number = {0},
pages = {74 - 89},
year = {2013},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/j.trb.2013.01.007},
url = {http://www.sciencedirect.com/science/article/pii/S0191261513000180},
author = {Kibrom A. Abay and Rajesh Paleti and Chandra R. Bhat},
keywords = {Multivariate ordered-response probit},
keywords = {Crash analysis},
keywords = {Injury severity modeling},
keywords = {Seat belt use endogeneity},
keywords = {Offsetting behavior},
keywords = {Maximum simulated likelihood },
abstract = {The current study contributes to the existing injury severity modeling literature by developing a multivariate probit model of injury severity and seat belt use decisions of both drivers involved in two-vehicle crashes. The modeling approach enables the joint modeling of the injury severity of multiple individuals involved in a crash, while also recognizing the endogeneity of seat belt use in predicting injury severity levels as well as accommodating unobserved heterogeneity in the effects of variables. The proposed model is applied to analyze the injury severity of drivers involved in two-vehicle road crashes in Denmark. The empirical analysis provides strong support for the notion that people offset the restraint benefits of seat belt use by driving more aggressively. Also, men and those individuals driving heavy vehicles have a lower injury risk than women and those driving lighter vehicles, respectively. At the same time, men and individuals driving heavy vehicles pose more of a danger to other drivers on the roadway when involved in a crash. Other important determinants of injury severity include speed limit on roadways where crash occurs, the presence (or absence) of center dividers (median barriers), and whether the crash involves a head-on collision. These and other results are discussed, along with implications for countermeasures to reduce injury severities in crashes. The analysis also underscores the importance of considering injury severity at a crash level, while accommodating seat belt endogeneity effects and unobserved heterogeneity effects. }
}
@article{Narayanamoorthy2013245,
title = {On accommodating spatial dependence in bicycle and pedestrian injury counts by severity level },
journal = {Transportation Research Part B: Methodological },
volume = {55},
number = {0},
pages = {245 - 264},
year = {2013},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/j.trb.2013.07.004},
url = {http://www.sciencedirect.com/science/article/pii/S0191261513001197},
author = {Sriram Narayanamoorthy and Rajesh Paleti and Chandra R. Bhat},
keywords = {Multivariate count data},
keywords = {Spatial econometrics},
keywords = {Crash analysis},
keywords = {Composite marginal likelihood },
abstract = {Abstract This paper proposes a new spatial multivariate count model to jointly analyze the traffic crash-related counts of pedestrians and bicyclists by injury severity. The modeling framework is applied to predict injury counts at a Census tract level, based on crash data from Manhattan, New York. The results highlight the need to use a multivariate modeling system for the analysis of injury counts by road-user type and injury severity level, while also accommodating spatial dependence effects in injury counts. }
}
@article{Castro2013188,
title = {A spatial generalized ordered response model to examine highway crash injury severity },
journal = {Accident Analysis & Prevention },
volume = {52},
number = {0},
pages = {188 - 203},
year = {2013},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2012.12.009},
url = {http://www.sciencedirect.com/science/article/pii/S0001457512004319},
author = {Marisol Castro and Rajesh Paleti and Chandra R. Bhat},
keywords = {Highway crash injury severity},
keywords = {Generalized ordered response model},
keywords = {Unobserved heterogeneity},
keywords = {Spatial dependence},
keywords = {Composite marginal likelihood},
keywords = {Spatial econometrics },
abstract = {This paper proposes a flexible econometric structure for injury severity analysis at the level of individual crashes that recognizes the ordinal nature of injury severity categories, allows unobserved heterogeneity in the effects of contributing factors, as well as accommodates spatial dependencies in the injury severity levels experienced in crashes that occur close to one another in space. The modeling framework is applied to analyze the injury severity sustained in crashes occurring on highway road segments in Austin, Texas. The sample is drawn from the Texas Department of Transportation (TxDOT) crash incident files from 2009 and includes a variety of crash characteristics, highway design attributes, driver and vehicle characteristics, and environmental factors. The results from our analysis underscore the value of our proposed model for data fit purposes as well as to accurately estimate variable effects. The most important determinants of injury severity on highways, according to our results, are (1) whether any vehicle occupant is ejected, (2) whether collision type is head-on, (3) whether any vehicle involved in the crash overturned, (4) whether any vehicle occupant is unrestrained by a seat-belt, and (5) whether a commercial truck is involved. }
}
@article{Bricka201267,
title = {An analysis of the factors influencing differences in survey-reported and GPS-recorded trips },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {21},
number = {1},
pages = {67 - 88},
year = {2012},
note = {},
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/j.trc.2011.09.005},
url = {http://www.sciencedirect.com/science/article/pii/S0968090X11001410},
author = {Stacey G. Bricka and Sudeshna Sen and Rajesh Paleti and Chandra R. Bhat},
keywords = {Travel behavior},
keywords = {\{GPS\} technology},
keywords = {Travel survey data collection techniques},
keywords = {Trip detection algorithms },
abstract = {Recent advances in global positioning systems (GPS) technology have resulted in a transition in household travel survey methods to test the use of \{GPS\} units to record travel details, followed by the application of an algorithm to both identify trips and impute trip purpose, typically supplemented with some level of respondent confirmation via prompted-recall surveys. As the research community evaluates this new approach to potentially replace the traditional survey-reported collection method, it is important to consider how well the GPS-recorded and algorithm-imputed details capture trip details and whether the traditional survey-reported collection method may be preferred with regards to some types of travel. This paper considers two measures of travel intensity (survey-reported and GPS-recorded) for two trip purposes (work and non-work) as dependent variables in a joint ordered response model. The empirical analysis uses a sample from the full-study of the 2009 Indianapolis regional household travel survey. Individuals in this sample provided diary details about their travel survey day as well as carried wearable \{GPS\} units for the same 24-h period. The empirical results provide important insights regarding differences in measures of travel intensities related to the two different data collection modes (diary and GPS). The results suggest that more research is needed in the development of workplace identification algorithms, that \{GPS\} should continue to be used alongside rather than in lieu of the traditional diary approach, and that assignment of individuals to the \{GPS\} or diary survey approach should consider demographics and other characteristics. }
}
@article{Castro2012253,
title = {A latent variable representation of count data models to accommodate spatial and temporal dependence: Application to predicting crash frequency at intersections },
journal = {Transportation Research Part B: Methodological },
volume = {46},
number = {1},
pages = {253 - 272},
year = {2012},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/j.trb.2011.09.007},
url = {http://www.sciencedirect.com/science/article/pii/S0191261511001366},
author = {Marisol Castro and Rajesh Paleti and Chandra R. Bhat},
keywords = {Count data},
keywords = {Multivariate analysis},
keywords = {Spatial econometrics},
keywords = {Accident analysis},
keywords = {Composite marginal likelihood},
keywords = {Generalized ordered response },
abstract = {This paper proposes a reformulation of count models as a special case of generalized ordered-response models in which a single latent continuous variable is partitioned into mutually exclusive intervals. Using this equivalent latent variable-based generalized ordered response framework for count data models, we are then able to gainfully and efficiently introduce temporal and spatial dependencies through the latent continuous variables. Our formulation also allows handling excess zeros in correlated count data, a phenomenon that is commonly found in practice. A composite marginal likelihood inference approach is used to estimate model parameters. The modeling framework is applied to predict crash frequency at urban intersections in Arlington, Texas. The sample is drawn from the Texas Department of Transportation (TxDOT) crash incident files between 2003 and 2009, resulting in 1190 intersection-year observations. The results reveal the presence of intersection-specific time-invariant unobserved components influencing crash propensity and a spatial lag structure to characterize spatial dependence. Roadway configuration, approach roadway functional types, traffic control type, total daily entering traffic volumes and the split of volumes between approaches are all important variables in determining crash frequency at intersections. }
}
@comment{{Chandra R. Bhat PAPERS}}
@article{Bhat201468,
title = {A new estimation approach to integrate latent psychological constructs in choice modeling },
journal = {Transportation Research Part B: Methodological },
volume = {67},
number = {0},
pages = {68 - 85},
year = {2014},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/j.trb.2014.04.011},
url = {http://www.sciencedirect.com/science/article/pii/S0191261514000678},
author = {Chandra R. Bhat and Subodh K. Dubey},
keywords = {Multinomial probit},
keywords = {\{ICLV\} models},
keywords = {\{MACML\} estimation approach },
abstract = {Abstract In the current paper, we propose a new multinomial probit-based model formulation for integrated choice and latent variable (ICLV) models, which, as we show in the paper, has several important advantages relative to the traditional logit kernel-based \{ICLV\} formulation. Combining this MNP-based \{ICLV\} model formulation with Bhat’s maximum approximate composite marginal likelihood (MACML) inference approach resolves the specification and estimation challenges that are typically encountered with the traditional \{ICLV\} formulation estimated using simulation approaches. Our proposed approach can provide very substantial computational time advantages, because the dimensionality of integration in the log-likelihood function is independent of the number of latent variables. Further, our proposed approach easily accommodates ordinal indicators for the latent variables, as well as combinations of ordinal and continuous response indicators. The approach can be extended in a relatively straightforward fashion to also include nominal indicator variables. A simulation exercise in the virtual context of travel mode choice shows that the \{MACML\} inference approach is very effective at recovering parameters. The time for convergence is of the order of 30–80 min for sample sizes ranging from 500 observations to 2000 observations, in contrast to much longer times for convergence experienced in typical \{ICLV\} model estimations. }
}
@article{Bhat20131,
title = {A new estimation approach for the multiple discrete–continuous probit (MDCP) choice model },
journal = {Transportation Research Part B: Methodological },
volume = {55},
number = {0},
pages = {1 - 22},
year = {2013},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/j.trb.2013.04.005},
url = {http://www.sciencedirect.com/science/article/pii/S0191261513000738},
author = {Chandra R. Bhat and Marisol Castro and Mubassira Khan},
keywords = {Multiple discrete–continuous model},
keywords = {Maximum approximate composite marginal likelihood},
keywords = {Recreation choice },
abstract = {Abstract This paper develops a blueprint (complete with matrix notation) to apply Bhat’s (2011) Maximum Approximate Composite Marginal Likelihood (MACML) inference approach for the estimation of cross-sectional as well as panel multiple discrete–continuous probit (MDCP) models. A simulation exercise is undertaken to evaluate the ability of the proposed approach to recover parameters from a cross-sectional \{MDCP\} model. The results show that the \{MACML\} approach does very well in recovering parameters, as well as appears to accurately capture the curvature of the Hessian of the log-likelihood function. The paper also demonstrates the application of the proposed approach through a study of individuals’ recreational (i.e., long distance leisure) choice among alternative destination locations and the number of trips to each recreational destination location, using data drawn from the 2004 to 2005 Michigan statewide household travel survey. }
}
@article{Bernardo2015,
title = {An empirical investigation into the time-use and activity patterns of dual-earner couples with and without young children },
journal = {Transportation Research Part A: Policy and Practice },
volume = {},
number = {0},
pages = { - },
year = {2015},
note = {},
issn = {0965-8564},
doi = {http://dx.doi.org/10.1016/j.tra.2014.12.006},
url = {http://www.sciencedirect.com/science/article/pii/S0965856414002985},
author = {Christina Bernardo and Rajesh Paleti and Megan Hoklas and Chandra Bhat},
keywords = {Time-use},
keywords = {Dual-earner households},
keywords = {Social exclusion},
keywords = {Time poverty},
keywords = {Work-family balance},
keywords = {Multiple-discrete choices },
abstract = {Abstract This paper examines the time-use patterns of adults in dual-earner households with and without children as a function of several individual and household socio-demographics and employment characteristics. A disaggregate activity purpose classification including both in-home and out-of-home activity pursuits is used because of the travel demand relevance of out-of-home pursuits, as well as to examine both mobility-related and general time-use related social exclusion and time poverty issues. The study uses the Nested Multiple Discrete Continuous Extreme Value (MDCNEV) model, which recognizes that time-decisions entail the choice of participating in one or more activity purposes along with the amount of time to invest in each chosen activity purpose, and allows generic correlation structures to account for common unobserved factors that might impact the choice of multiple alternatives. The 2010 American Time Use Survey (ATUS) data is used for the empirical analysis. A major finding of the study is that the presence of a child in dual-earner households not only leads to a reduction in in-home non-work activity participation (excluding child care activities) but also a substantially larger decrease in out-of-home non-work activity participation (excluding child care and shopping activities), suggesting a higher level of mobility-related social exclusion relative to overall time-use social exclusion. To summarize, the results in the paper underscore the importance of considering household structure in activity-based travel demand models, as well as re-designing work policies in the United States to facilitate a reduction in work-family conflict in dual-earner families. }
}
@article{Bhat201431,
title = {A joint count-continuous model of travel behavior with selection based on a multinomial probit residential density choice model },
journal = {Transportation Research Part B: Methodological },
volume = {68},
number = {0},
pages = {31 - 51},
year = {2014},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/j.trb.2014.05.004},
url = {http://www.sciencedirect.com/science/article/pii/S0191261514000770},
author = {Chandra R. Bhat and Sebastian Astroza and Raghuprasad Sidharthan and Mohammad Jobair Bin Alam and Waleed H. Khushefati},
keywords = {Multivariate dependency},
keywords = {Self-selection},
keywords = {Treatment effects},
keywords = {Maximum Approximate Composite Marginal Likelihood},
keywords = {Land-use and built environment},
keywords = {Travel behavior },
abstract = {Abstract This paper formulates a multidimensional choice model system that is capable of handling multiple nominal variables, multiple count dependent variables, and multiple continuous dependent variables. The system takes the form of a treatment-outcome selection system with multiple treatments and multiple outcome variables. The Maximum Approximate Composite Marginal Likelihood (MACML) approach is proposed in estimation, and a simulation experiment is undertaken to evaluate the ability of the \{MACML\} method to recover the model parameters in such integrated systems. These experiments show that our estimation approach recovers the underlying parameters very well and is efficient from an econometric perspective. The parametric model system proposed in the paper is applied to an analysis of household-level decisions on residential location, motorized vehicle ownership, the number of daily motorized tours, the number of daily non-motorized tours, and the average distance for the motorized tours. The empirical analysis uses the \{NHTS\} 2009 data from the San Francisco Bay area. Model estimation results show that the choice dimensions considered in this paper are inter-related, both through direct observed structural relationships and through correlations across unobserved factors (error terms) affecting multiple choice dimensions. The significant presence of self-selection effects (endogeneity) suggests that modeling the various choice processes in an independent sequence of models is not reflective of the true relationships that exist across these choice dimensions, as also reinforced through the computation of treatment effects in the paper. }
}
@article{Bhat2012817,
title = {A new approach to specify and estimate non-normally mixed multinomial probit models },
journal = {Transportation Research Part B: Methodological },
volume = {46},
number = {7},
pages = {817 - 833},
year = {2012},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/j.trb.2012.02.007},
url = {http://www.sciencedirect.com/science/article/pii/S019126151200032X},
author = {Chandra R. Bhat and Raghuprasad Sidharthan},
keywords = {Multinomial probit},
keywords = {Mixed models},
keywords = {Maximum approximate composite marginal likelihood},
keywords = {Maximum simulated likelihood},
keywords = {Multivariate skew-normal distribution },
abstract = {The current paper proposes the use of the multivariate skew-normal distribution function to accommodate non-normal mixing in cross-sectional and panel multinomial probit (MNP) models. The combination of skew-normal mixing and the \{MNP\} kernel lends itself nicely to estimation using Bhat’s (2011) maximum approximate composite marginal likelihood (MACML) approach. Simulation results for the cross-sectional case show that our proposed approach does well in recovering the underlying parameters, and also highlights the pitfalls of ignoring non-normality of the continuous mixing distribution when such non-normality is present. At the same time, the proposed model obviates the need to assume a pre-specified parametric distribution for the mixing, and allows the estimation of a very flexible, but still parsimonious, mixing distribution form. }
}
@article{Bhat201477,
title = {A multivariate hurdle count data model with an endogenous multiple discrete–continuous selection system },
journal = {Transportation Research Part B: Methodological },
volume = {63},
number = {0},
pages = {77 - 97},
year = {2014},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/j.trb.2014.02.006},
url = {http://www.sciencedirect.com/science/article/pii/S0191261514000320},
author = {Chandra R. Bhat and Sebastian Astroza and Raghuprasad Sidharthan and Prerna C. Bhat},
keywords = {Multivariate count data},
keywords = {Generalized ordered-response},
keywords = {Multiple discrete–continuous models},
keywords = {Hurdle model system},
keywords = {Endogeneity },
abstract = {Abstract This paper proposes a new econometric formulation and an associated estimation method for multivariate count data that are themselves observed conditional on a participation selection system that takes a multiple discrete–continuous model structure. This leads to a joint model system of a multivariate count and a multiple discrete–continuous selection system in a hurdle-type model. The model is applied to analyze the participation and time investment of households in out-of-home activities by activity purpose, along with the frequency of participation in each selected activity. The results suggest that the number of episodes of activities as well as the time investment in those activities may be more of a lifestyle- and lifecycle-driven choice than one related to the availability of opportunities for activity participation. }
}
@article{Pinjari2010562,
title = {A multiple discrete–continuous nested extreme value (MDCNEV) model: Formulation and application to non-worker activity time-use and timing behavior on weekdays },
journal = {Transportation Research Part B: Methodological },
volume = {44},
number = {4},
pages = {562 - 583},
year = {2010},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/j.trb.2009.08.001},
url = {http://www.sciencedirect.com/science/article/pii/S019126150900099X},
author = {Abdul Rawoof Pinjari and Chandra Bhat},
keywords = {Multiple discrete-continuous choices},
keywords = {Random utility maximization},
keywords = {Kuhn–Tucker demand model systems},
keywords = {Flexible substitution patterns},
keywords = {Activity time-use},
keywords = {Activity timing },
abstract = {This paper develops a multiple discrete–continuous nested extreme value (MDCNEV) model that relaxes the independently distributed (or uncorrelated) error terms assumption of the multiple discrete–continuous extreme value (MDCEV) model proposed by Bhat [Bhat, C.R., 2005. A multiple discrete–continuous extreme value model: formulation and application to discretionary time-use decisions. Transportation Research Part B 39 (8), 679–707; Bhat, C.R., 2008. The multiple discrete–continuous extreme value (MDCEV) model: role of utility function parameters, identification considerations, and model extensions. Transportation Research Part B 42 (3), 274–303]. The \{MDCNEV\} model captures inter-alternative correlations among alternatives in mutually exclusive subsets (or nests) of the choice set, while maintaining the closed-form of probability expressions for any (and all) consumption pattern(s). The \{MDCNEV\} model is applied to analyze non-worker out-of-home discretionary activity time-use and activity timing decisions on weekdays using data from the 2000 San Francisco Bay Area data. This empirical application contributes to the literature on activity time-use and activity timing analysis by considering daily activity time-use behavior and activity timing preferences in a unified utility maximization-based framework. The model estimation results provide several insights into the determinants of non-workers’ activity time-use and timing decisions. The \{MDCNEV\} model performs better than the \{MDCEV\} model in terms of goodness of fit. However, the nesting parameters are very close to 1, indicating low levels of correlation. Nonetheless, even with such low correlation levels, empirical policy simulations indicate non-negligible differences in policy predictions and substitution patterns exhibited by the two models. Experiments conducted using simulated data also corroborate this result. }
}
@article{Bhat2008274,
title = {The multiple discrete-continuous extreme value (MDCEV) model: Role of utility function parameters, identification considerations, and model extensions },
journal = {Transportation Research Part B: Methodological },
volume = {42},
number = {3},
pages = {274 - 303},
year = {2008},
note = {A Tribute to the Career of Frank Koppelman },
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/j.trb.2007.06.002},
url = {http://www.sciencedirect.com/science/article/pii/S0191261507000677},
author = {Chandra R. Bhat},
keywords = {Discrete-continuous system},
keywords = {Multiple discreteness},
keywords = {Kuhn–Tucker demand systems},
keywords = {Mixed discrete choice},
keywords = {Random utility maximization },
abstract = {Many consumer choice situations are characterized by the simultaneous demand for multiple alternatives that are imperfect substitutes for one another. A simple and parsimonious multiple discrete-continuous extreme value (MDCEV) econometric approach to handle such multiple discreteness was formulated by Bhat (2005) [Bhat, C.R., 2005. A multiple discrete-continuous extreme value model: formulation and application to discretionary time-use decisions. Transportation Research Part B 39(8), 679–707]. within the broader Kuhn–Tucker (KT) multiple discrete-continuous economic consumer demand model of Wales and Woodland (1983) [Wales, T.J., and Woodland, A.D., 1983. Estimation of consumer demand systems with binding non-negativity constraints. Journal of Econometrics 21(3), 263–85]. This paper examines several issues associated with the \{MDCEV\} model and other extant \{KT\} multiple discrete-continuous models. Specifically, the paper proposes a new utility function form that enables clarity in the role of each parameter in the utility specification, presents identification considerations associated with both the utility functional form as well as the stochastic nature of the utility specification, extends the \{MDCEV\} model to the case of price variation across goods and to general error covariance structures, discusses the relationship between earlier KT-based multiple discrete-continuous models, and illustrates the many technical nuances and identification considerations of the multiple discrete-continuous model structure through empirical examples. The paper also highlights the technical problems associated with the stochastic specification used in the KT-based multiple discrete-continuous models formulated in recent Environmental Economics papers. }
}
@article{Paleti201324,
title = {The composite marginal likelihood (CML) estimation of panel ordered-response models },
journal = {Journal of Choice Modelling },
volume = {7},
number = {0},
pages = {24 - 43},
year = {2013},
note = {},
issn = {1755-5345},
doi = {http://dx.doi.org/10.1016/j.jocm.2013.04.006},
url = {http://www.sciencedirect.com/science/article/pii/S1755534513000110},
author = {Rajesh Paleti and Chandra R. Bhat},
keywords = {Ordered-response model},
keywords = {Simulated likelihood},
keywords = {Composite marginal likelihood},
keywords = {Cross-sectional model},
keywords = {Panel model },
abstract = {Abstract In the context of panel ordered-response structures, the current paper compares the performance of the maximum-simulated likelihood (MSL) inference approach and the composite marginal likelihood (CML) inference approach. The panel structures considered include the pure random coefficients (RC) model with no autoregressive error component, as well as the more general case of random coefficients combined with an autoregressive error component. The ability of the \{MSL\} and \{CML\} approaches to recover the true parameters is examined using simulated datasets. The results indicate that the performances of the \{MSL\} approach (with 150 scrambled and randomized Halton draws) and the simulation-free \{CML\} approach are of about the same order in all panel structures in terms of the absolute percentage bias (APB) of the parameters and econometric efficiency. However, the simulation-free \{CML\} approach exhibits no convergence problems of the type that affect the \{MSL\} approach. At the same time, the \{CML\} approach is about 5–12 times faster than the \{MSL\} approach for the simple random coefficients panel structure, and about 100 times faster than the \{MSL\} approach when an autoregressive error component is added. As the number of random coefficients increases, or if higher order autoregressive error structures are considered, one can expect even higher computational efficiency factors for the \{CML\} over the \{MSL\} approach. These results are promising for the use of the \{CML\} method for the quick, accurate, and practical estimation of panel ordered-response models with flexible and rich stochastic specifications. }
}
@article{Bhat201453,
title = {A count data model with endogenous covariates: Formulation and application to roadway crash frequency at intersections },
journal = {Analytic Methods in Accident Research },
volume = {1},
number = {0},
pages = {53 - 71},
year = {2014},
note = {},
issn = {2213-6657},
doi = {http://dx.doi.org/10.1016/j.amar.2013.10.001},
url = {http://www.sciencedirect.com/science/article/pii/S2213665713000043},
author = {Chandra R. Bhat and Kathryn Born and Raghuprasad Sidharthan and Prerna C. Bhat},
keywords = {Count data},
keywords = {Treatment-outcome models},
keywords = {Accident analysis},
keywords = {Generalized ordered response},
keywords = {Flashing light control },
abstract = {Abstract This paper proposes an estimation approach for count data models with endogenous covariates. The maximum approximate composite marginal likelihood inference approach is used to estimate model parameters. The modeling framework is applied to predict crash frequency at urban intersections in Irving, Texas. The sample is drawn from the Texas Department of Transportation (TxDOT) crash incident files for the year 2008. The results highlight the importance of accommodating endogeneity effects in count models. In addition, the results reveal the increased propensity for crashes at intersections with flashing lights, intersections with crest approaches, and intersections that are on frontage roads. }
}
@article{Bhat2011940,
title = {A simulation evaluation of the maximum approximate composite marginal likelihood (MACML) estimator for mixed multinomial probit models },
journal = {Transportation Research Part B: Methodological },
volume = {45},
number = {7},
pages = {940 - 953},
year = {2011},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/j.trb.2011.04.006},
url = {http://www.sciencedirect.com/science/article/pii/S0191261511000506},
author = {Chandra R. Bhat and Raghuprasad Sidharthan},
keywords = {Mixed multinomial probit},
keywords = {Composite marginal likelihood},
keywords = {Maximum simulated likelihood},
keywords = {Discrete choice models},
keywords = {Unordered-response models},
keywords = {Panel data },
abstract = {This paper evaluates the ability of the maximum approximate composite marginal likelihood (MACML) estimation approach to recover parameters from finite samples in mixed cross-sectional and panel multinomial probit models. Comparisons with the maximum simulated likelihood (MSL) estimation approach are also undertaken. The results indicate that the \{MACML\} approach recovers parameters much more accurately than the \{MSL\} approach in all model structures and covariance specifications. The \{MACML\} inference approach also estimates the parameters efficiently, with the asymptotic standard errors being, in general, only a small proportion of the true values. As importantly, the \{MACML\} inference approach takes only a very small fraction of the time needed for \{MSL\} estimation. In particular, the results suggest that, for the case of five random coefficients, the \{MACML\} approach is about 50 times faster than the \{MSL\} for the cross-sectional random coefficients case, about 15 times faster than the \{MSL\} for the panel inter-individual random coefficients case, and about 350 times or more faster than the \{MSL\} for the panel intra- and inter-individual random coefficients case. As the number of alternatives in the unordered-response model increases, one can expect even higher computational efficiency factors for the \{MACML\} over the \{MSL\} approach. Further, as should be evident in the panel intra- and inter-individual random coefficients case, the \{MSL\} is all but practically infeasible when the mixing structure leads to an explosion in the dimensionality of integration in the likelihood function, but these situations are handled with ease in the \{MACML\} approach. It is hoped that the \{MACML\} procedure will spawn empirical research into rich model specifications within the context of unordered multinomial choice modeling, including autoregressive random coefficients, dynamics in coefficients, space–time effects, and spatial/social interactions. }
}
@article{Castro2012729,
title = {Accommodating multiple constraints in the multiple discrete–continuous extreme value (MDCEV) choice model },
journal = {Transportation Research Part B: Methodological },
volume = {46},
number = {6},
pages = {729 - 743},
year = {2012},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/j.trb.2012.02.005},
url = {http://www.sciencedirect.com/science/article/pii/S0191261512000203},
author = {Marisol Castro and Chandra R. Bhat and Ram M. Pendyala and Sergio R. Jara-Díaz},
keywords = {Travel demand},
keywords = {Multiple discrete–continuous extreme value model},
keywords = {Multiple constraints},
keywords = {Time use},
keywords = {Consumer theory },
abstract = {Multiple-discrete continuous choice models formulated and applied in recent years consider a single linear resource constraint, which, when combined with consumer preferences, determines the optimal consumption point. However, in reality, consumers face multiple resource constraints such as those associated with time, money, and capacity. Ignoring such multiple constraints and instead using a single constraint can, and in general will, lead to poor data fit and inconsistent preference estimation, which can then have a serious negative downstream effect on forecasting and welfare/policy analysis. In this paper, we extend the multiple-discrete continuous extreme value (MDCEV) model to accommodate multiple constraints. The formulation uses a flexible and general utility function form, and is applicable to the case of complete demand systems as well as incomplete demand systems. The proposed MC-MDCEV model is applied to time-use decisions, where individuals are assumed to maximize their utility from time-use in one or more activities subject to monetary and time availability constraints. The sample for the empirical exercise is generated by combining time-use information from the 2008 American Time Use Survey and expenditure records from the 2008 \{US\} Consumer Expenditure Survey. The estimation results show that preferences can get severely mis-estimated, and the data fit can degrade substantially, when only a subset of active resource constraints is used. }
}
@article{Bhat2012273,
title = {Recent developments in discrete choice model formulation, estimation, and inference },
journal = {Transportation Research Part B: Methodological },
volume = {46},
number = {2},
pages = {273 - 275},
year = {2012},
note = {Emerging and Innovative Directions in Choice Modeling },
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/j.trb.2011.10.007},
url = {http://www.sciencedirect.com/science/article/pii/S0191261511001470},
author = {Chandra R. Bhat},
keywords = {Quasi-Monte Carlo techniques},
keywords = {Social interactions},
keywords = {Consideration sets},
keywords = {Delta method},
keywords = {Expectation maximization },
abstract = {The developments in discrete choice formulation, estimation and inference techniques have been fast and furious over the past few years. This special issue of Transportation Research Part B is a compilation of some of the cutting-edge research in the field. }
}
@article{Bhat2011923,
title = {The maximum approximate composite marginal likelihood (MACML) estimation of multinomial probit-based unordered response choice models },
journal = {Transportation Research Part B: Methodological },
volume = {45},
number = {7},
pages = {923 - 939},
year = {2011},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/j.trb.2011.04.005},
url = {http://www.sciencedirect.com/science/article/pii/S019126151100049X},
author = {Chandra R. Bhat},
keywords = {Multinomial probit},
keywords = {Mixed models},
keywords = {Composite marginal likelihood},
keywords = {Discrete choice models},
keywords = {Spatial econometrics},
keywords = {Panel data },
abstract = {The likelihood functions of multinomial probit (MNP)-based choice models entail the evaluation of analytically-intractable integrals. As a result, such models are usually estimated using maximum simulated likelihood (MSL) techniques. Unfortunately, for many practical situations, the computational cost to ensure good asymptotic \{MSL\} estimator properties can be prohibitive and practically infeasible as the number of dimensions of integration rises. In this paper, we introduce a maximum approximate composite marginal likelihood (MACML) estimation approach for \{MNP\} models that can be applied using simple optimization software for likelihood estimation. It also represents a conceptually and pedagogically simpler procedure relative to simulation techniques, and has the advantage of substantial computational time efficiency relative to the \{MSL\} approach. The paper provides a “blueprint” for the \{MACML\} estimation for a wide variety of \{MNP\} models. }
}
@article{HolguínVeras201217,
title = {An assessment of the impacts of inspection times on the airline industry’s market share after September 11th },
journal = {Journal of Air Transport Management },
volume = {23},
number = {0},
pages = {17 - 24},
year = {2012},
note = {},
issn = {0969-6997},
doi = {http://dx.doi.org/10.1016/j.jairtraman.2012.02.004},
url = {http://www.sciencedirect.com/science/article/pii/S0969699712000646},
author = {José Holguín-Veras and Ning Xu and Chandra Bhat},
keywords = {Airport security screening},
keywords = {Behavioral impacts},
keywords = {Discrete choice modeling},
keywords = {Extreme events},
keywords = {Mixed logit },
abstract = {This paper studies the behavioral changes produced by the events of September 11th, 2001 on intercity air travel behavior, the impacts that increases in security inspection times had on the airline industry’s market share, and the economic optimality of inspection time goals. We develop an modeling framework is developed that includes a discrete choice models estimated with stated preference data collected after September 11th to assess passenger behavior changes, a discrete event simulation of security screening operations to quantify the performance of alternative screening configurations, and an economic formulation to compute welfare. The modeling system is then applied to an idealized airport, based on composite data from two real life airports, to gain insight into the impacts of security screening configurations and to identify the optimal inspection time. }
}
@article{Bhat2007506,
title = {A comprehensive analysis of built environment characteristics on household residential choice and auto ownership levels },
journal = {Transportation Research Part B: Methodological },
volume = {41},
number = {5},
pages = {506 - 526},
year = {2007},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/j.trb.2005.12.005},
url = {http://www.sciencedirect.com/science/article/pii/S0191261506001196},
author = {Chandra R. Bhat and Jessica Y. Guo},
keywords = {Built environment},
keywords = {Residential sorting},
keywords = {Self-selection},
keywords = {Auto ownership},
keywords = {Integrated land use-transportation modeling },
abstract = {There has been an increasing interest in the land use-transportation connection in the past decade, motivated by the possibility that design policies associated with the built environment can be used to control, manage, and shape individual traveler behavior and aggregate travel demand. In this line of research and application pursuit, it is critical to understand whether the empirically observed association between the built environment and travel behavior-related variables is a true reflection of underlying causality or simply a spurious correlation attributable to the intervening relationship between the built environment and the characteristics of people who choose to live in particular built environments. In this research paper, we identify the research designs and methodologies that may be used to test the presence of “true” causality versus residential sorting-based “spurious” associations in the land-use transportation connection. The paper then develops a methodological formulation to control for residential sorting effects in the analysis of the effect of built environment attributes on travel behavior-related choices. The formulation is applied to comprehensively examine the impact of the built environment, transportation network attributes, and demographic characteristics on residential choice and car ownership decisions. The model formulation takes the form of a joint mixed multinomial logit-ordered response structure that (a) accommodates differential sensitivity to the built environment and transportation network variables due to both demographic and unobserved household attributes and (b) controls for the self-selection of individuals into neighborhoods based on car ownership preferences stemming from both demographic characteristics and unobserved household factors. The analysis in the paper represents, to our knowledge, the first instance of the formulation and application of a unified mixed multinomial logit-ordered response structure in the econometric literature. The empirical analysis in the paper is based on the residential choice and car ownership decisions of San Francisco Bay area residents. }
}
@article{Bhat2009749,
title = {A copula-based approach to accommodate residential self-selection effects in travel behavior modeling },
journal = {Transportation Research Part B: Methodological },
volume = {43},
number = {7},
pages = {749 - 765},
year = {2009},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/j.trb.2009.02.001},
url = {http://www.sciencedirect.com/science/article/pii/S0191261509000204},
author = {Chandra R. Bhat and Naveen Eluru},
keywords = {Copula},
keywords = {Multivariate dependency},
keywords = {Self-selection},
keywords = {Treatment effects},
keywords = {Vehicle miles of travel},
keywords = {Maximum likelihood},
keywords = {Archimedean copulas },
abstract = {The dominant approach in the literature to dealing with sample selection is to assume a bivariate normality assumption directly on the error terms, or on transformed error terms, in the discrete and continuous equations. Such an assumption can be restrictive and inappropriate, since the implication is a linear and symmetrical dependency structure between the error terms. In this paper, we introduce and apply a flexible approach to sample selection in the context of built environment effects on travel behavior. The approach is based on the concept of a “copula”, which is a multivariate functional form for the joint distribution of random variables derived purely from pre-specified parametric marginal distributions of each random variable. The copula concept has been recognized in the statistics field for several decades now, but it is only recently that it has been explicitly recognized and employed in the econometrics field. The copula-based approach retains a parametric specification for the bivariate dependency, but allows testing of several parametric structures to characterize the dependency. The empirical context in the current paper is a model of residential neighborhood choice and daily household vehicle miles of travel (VMT), using the 2000 San Francisco Bay Area Household Travel Survey (BATS). The sample selection hypothesis is that households select their residence locations based on their travel needs, which implies that observed \{VMT\} differences between households residing in neo-urbanist and conventional neighborhoods cannot be attributed entirely to the built environment variations between the two neighborhoods types. The results indicate that, in the empirical context of the current study, the \{VMT\} differences between households in different neighborhood types may be attributed to both built environment effects and residential self-selection effects. As importantly, the study indicates that use of a traditional Gaussian bivariate distribution to characterize the relationship in errors between residential choice and \{VMT\} can lead to misleading implications about built environment effects. }
}
@article{Sener2011294,
title = {Accommodating spatial correlation across choice alternatives in discrete choice models: an application to modeling residential location choice behavior },
journal = {Journal of Transport Geography },
volume = {19},
number = {2},
pages = {294 - 303},
year = {2011},
note = {},
issn = {0966-6923},
doi = {http://dx.doi.org/10.1016/j.jtrangeo.2010.03.013},
url = {http://www.sciencedirect.com/science/article/pii/S0966692310000451},
author = {Ipek N. Sener and Ram M. Pendyala and Chandra R. Bhat},
keywords = {Spatial correlation},
keywords = {Spatially correlated logit model},
keywords = {Residential location choice},
keywords = {Distance-decay function},
keywords = {Activity-travel behavior modeling},
keywords = {Discrete choice modeling },
abstract = {This paper presents a modeling methodology capable of accounting for spatial correlation across choice alternatives in discrete choice modeling applications. Many location choice (e.g., residential location, workplace location, destination location) modeling contexts involve choice sets where alternatives are spatially correlated with one another due to unobserved factors. In the presence of such spatial correlation, traditional discrete choice modeling methods that are often based on the assumption of independence among choice alternatives are not appropriate. In this paper, a Generalized Spatially Correlated Logit (GSCL) model that allows one to represent the degree of spatial correlation as a function of a multi-dimensional vector of attributes characterizing each pair of location choice alternatives is formulated and presented. The formulation of the \{GSCL\} model allows one to accommodate alternative correlation mechanisms rather than pre-imposing restrictive correlation assumptions on the location choice alternatives. The model is applied to the analysis of residential location choice behavior using a sample of households drawn from the 2000 San Francisco Bay Area Travel Survey (BATS) data set. Model estimation results obtained from the \{GSCL\} are compared against those obtained using the standard multinomial logit (MNL) model and the spatially correlated logit (SCL) model where only correlations across neighboring (or adjacent) alternatives are accommodated. Model findings suggest that there is significant spatial correlation across alternatives that do not share a common boundary, and that the \{GSCL\} offers the ability to more accurately capture spatial location choice behavior. }
}
@article{Pinjari2009729,
title = {Residential self-selection effects in an activity time-use behavior model },
journal = {Transportation Research Part B: Methodological },
volume = {43},
number = {7},
pages = {729 - 748},
year = {2009},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/j.trb.2009.02.002},
url = {http://www.sciencedirect.com/science/article/pii/S0191261509000198},
author = {Abdul Rawoof Pinjari and Chandra R. Bhat and David A. Hensher},
keywords = {Residential location choice},
keywords = {Residential self-selection},
keywords = {Time-use},
keywords = {Multiple Discrete-Continuous Extreme Value model},
keywords = {Integrated land-use transportation modeling },
abstract = {This study presents a joint model system of residential location and activity time-use choices that considers a comprehensive set of activity-travel environment (ATE) variables, as well as socio-demographic variables, as determinants of individual weekday activity time-use choices. The model system takes the form of a joint mixed Multinomial Logit–Multiple Discrete-Continuous Extreme Value (MNL–MDCEV) structure that (a) accommodates differential sensitivity to the \{ATE\} attributes due to both observed and unobserved individual-related attributes, and (b) controls for the self-selection of individuals into neighborhoods due to both observed and unobserved individual-related factors. The joint model system is estimated on a sample of 2793 households and individuals residing in Alameda County in the San Francisco Bay Area. The model results indicate the significant presence of residential self-selection effects due to both observed and unobserved individual-related factors. For instance, individuals from households with more bicycles are associated with a higher preference for out-of-home physically active pure recreational travel pursuits (such as bicycling around in the neighborhood). These same individuals locate into neighborhoods with good bicycling facilities. This leads to a non-causal association between individuals’ time investment in out-of-home physically active pure recreational travel and bicycling facilities in their residential neighborhoods. Thus, ignoring the effect of bicycle ownership in the time-use model, would lead to an inflated estimate of the effect of bicycling facility density on the time invested in physically active pure recreational travel. Similarly, there are significant unobserved individual factors that lead to a high preference for physically active recreational activities and also make individuals locate in areas with good bicycling facilities. When such unobserved factors were controlled by the proposed joint residential location and time-use model, the impact of bicycling facility density on out-of-home physically active recreational activities ceased to be statistically significant (from being statistically significant in the independent time-use model). These results highlight the need to control for residential self-selection effects when estimating the effects of the activity-travel environment on activity time-use choices. }
}
@article{LaMondia200870,
title = {An annual time use model for domestic vacation travel },
journal = {Journal of Choice Modelling },
volume = {1},
number = {1},
pages = {70 - 97},
year = {2008},
note = {},
issn = {1755-5345},
doi = {http://dx.doi.org/10.1016/S1755-5345(13)70023-X},
url = {http://www.sciencedirect.com/science/article/pii/S175553451370023X},
author = {Jeffrey LaMondia and Chandra R. Bhat and David A. Hensher},
keywords = {vacation},
keywords = {long distance},
keywords = {leisure activities},
keywords = {time use},
keywords = {choice modelling },
abstract = {Abstract Vacation travel in the USA, which constitutes about 25% of all long-distance travel, has been increasing consistently over the past two decades and warrants careful attention in the context of regional and statewide transportation air quality planning and policy analysis, as well as tourism marketing and service provision strategies. This paper contributes to the vacation travel literature by examining how households decide what vacation travel activities to participate in on an annual basis, and to what extent, given the total annual vacation travel time that is available at their disposal. To our knowledge, this is the first comprehensive modeling exercise in the literature to undertake such a vacation travel time-use analysis to examine purpose-specific time investments. A mixed multiple discrete-continuous extreme value (MDCEV) model structure that is consistent with the notion of “optimal arousal” in vacation type time-use decisions is used in the analysis. The data for the empirical analysis is drawn from the 1995 American Travel Survey (ATS). The results show that most households participate in different types of domestic vacation travel over the course of a year, and spend significantly different amounts of time on each type of vacation travel, based on household demographics, economic characteristics, and residence characteristics. }
}
@article{Bhat2008185,
title = {Frank Koppelman’s contributions and legacy to the travel demand modeling field },
journal = {Transportation Research Part B: Methodological },
volume = {42},
number = {3},
pages = {185 - 190},
year = {2008},
note = {A Tribute to the Career of Frank Koppelman },
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/j.trb.2007.09.001},
url = {http://www.sciencedirect.com/science/article/pii/S0191261507000914},
author = {Chandra R. Bhat and Laurie A. Garrow and Patricia L. Mokhtarian}
}
@article{Bhat2004573,
title = {On distinguishing between physically active and physically passive episodes and between travel and activity episodes: an analysis of weekend recreational participation in the San Francisco Bay area },
journal = {Transportation Research Part A: Policy and Practice },
volume = {38},
number = {8},
pages = {573 - 592},
year = {2004},
note = {},
issn = {0965-8564},
doi = {http://dx.doi.org/10.1016/j.tra.2004.04.002},
url = {http://www.sciencedirect.com/science/article/pii/S0965856404000527},
author = {Chandra Bhat and Allison Lockwood},
keywords = {Recreational activity},
keywords = {Weekend activity-travel patterns},
keywords = {Mixed multinomial logit},
keywords = {Physical activity},
keywords = {Activity-based travel analysis },
abstract = {This paper examines the out-of-home recreational episode participation of individuals over the weekend, with a specific focus on analyzing the determinants of participation in physically active versus physically passive pursuits and travel versus activity episodes (travel episodes correspond to recreational pursuits without any specific out-of-home location, such as walking, bicycling around the block, and joy-riding in a car, while activity episodes are pursued at a fixed out-of-home location, such as playing soccer at the soccer field and swimming at an aquatics center). The above disaggregation of recreational episodes facilitates the better analysis and modeling of activity-travel attributes, such as travel mode, episode duration, time-of-day of participation and location of participation. From a broader societal standpoint, the disaggregation of recreational episodes provides important information to encourage active participatory recreational pursuits, which can serve to relieve mental stress, improve the physical health of the population, and contribute to a socially vibrant society through increased interactions among individuals. The paper employs a mixed multinomial logit formulation for examining out-of-home recreational episode type participation using the 2000 San Francisco Bay area travel survey. A variety of variables, including individual and household sociodemographics, location attributes, and day of week and seasonal effects, are considered in the model specification. Individual-specific unobserved factors affecting the propensity to participate in different types of recreational episodes are also accommodated. }
}
@article{Bhat2002557,
title = {The spatial analysis of activity stop generation },
journal = {Transportation Research Part B: Methodological },
volume = {36},
number = {6},
pages = {557 - 575},
year = {2002},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/S0191-2615(01)00019-4},
url = {http://www.sciencedirect.com/science/article/pii/S0191261501000194},
author = {Chandra Bhat and Huimin Zhao},
keywords = {Spatial analysis},
keywords = {Multi-level modeling},
keywords = {Activity-based analysis},
keywords = {Simulated maximum likelihood},
keywords = {Halton sequences},
keywords = {Accessibility measure },
abstract = {Travel demand analysis is intrinsically spatial; yet spatial analysis considerations are seldom recognized and accommodated in travel modeling. The objective of this paper is to identify the spatial issues that need to be recognized in demand modeling, and to propose a multi-level, mixed logit, formulation to address these spatial issues in the context of activity stop generation. The multi-level model is estimated using the maximum simulated likelihood method. Empirical results obtained from applying the model to study shopping activity stop generation in the Boston Metropolitan area are presented and discussed. }
}
@article{Bhat20001,
title = {A comprehensive daily activity-travel generation model system for workers },
journal = {Transportation Research Part A: Policy and Practice },
volume = {34},
number = {1},
pages = {1 - 22},
year = {2000},
note = {},
issn = {0965-8564},
doi = {http://dx.doi.org/10.1016/S0965-8564(98)00037-8},
url = {http://www.sciencedirect.com/science/article/pii/S0965856498000378},
author = {Chandra R. Bhat and Sujit K. Singh},
keywords = {Activity–travel patern generation},
keywords = {Activity substitution},
keywords = {Time–space interaction},
keywords = {Ordered response variable},
keywords = {Joint unordered–ordered model system },
abstract = {This paper develops a comprehensive representation to describe the activity–travel pattern of workers and proposes an analysis framework to model the activity–travel attributes identified in the representation. The analysis framework is based on a descriptive examination of activity–travel patterns of workers from two locations in the US. The paper also formulates an econometric methodology to estimate the component of the analysis framework involving the joint modeling of evening commute mode choice, number of evening commute stops, and number of stops after arriving home from work. The methodology is applied to an empirical analysis using data from an activity survey conducted in the Boston Metropolitan area and the effects of a variety of congestion-alleviation measures are examined. © }
}
@article{Bhat2005255,
title = {A multidimensional mixed ordered-response model for analyzing weekend activity participation },
journal = {Transportation Research Part B: Methodological },
volume = {39},
number = {3},
pages = {255 - 278},
year = {2005},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/j.trb.2004.04.002},
url = {http://www.sciencedirect.com/science/article/pii/S0191261504000475},
author = {Chandra R. Bhat and Sivaramakrishnan Srinivasan},
keywords = {Multivariate mixed ordered response},
keywords = {Weekend activity participation},
keywords = {Activity-travel patterns},
keywords = {Simulated maximum likelihood},
keywords = {Day of week and season effects },
abstract = {The objective of this paper is to examine the frequency of participation of individuals in out-of-home non-work and non-school episodes over the weekend. A multivariate mixed ordered response formulation accommodating the effects of explanatory variables and capturing the dependence among the propensity to participate in different activity types is presented and applied using a San Francisco Bay area travel survey conducted in 2000. The results indicate the important effects of household sociodemographics (income, household structure, and bicycle ownership), individual sociodemographics (age, employment status, gender, and availability of driver's license), internet use, location effects, and day of week/seasonal effects. Interestingly, the results show that motorized vehicle ownership and urban form characteristics of the individual's neighborhood (land-use mix and density) do not have a statistically significant effect on stop-making propensity for any of the activity purposes. The lack of effects of these variables may be due to self-selection of individuals and households into neighborhoods based on their travel preferences. That is, individuals and households may locate themselves based on their motorized vehicle ownership preferences and mobility preferences. In addition to the effect of several variables on stop-making, the model also reveals substitution and complementarity effects among different activity types due to unobserved factors. }
}
@article{Bhat2004767,
title = {A mixed multinomial logit model analysis of weekend recreational episode type choice },
journal = {Transportation Research Part B: Methodological },
volume = {38},
number = {9},
pages = {767 - 787},
year = {2004},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/j.trb.2003.10.003},
url = {http://www.sciencedirect.com/science/article/pii/S0191261503001310},
author = {Chandra R. Bhat and Rachel Gossen},
keywords = {Weekend activity-pattern},
keywords = {Recreational activity},
keywords = {Mixed logit},
keywords = {Activity-based travel modeling },
abstract = {This paper presents a model for the type of recreational activity episodes that individuals pursue during the weekend. The choice set characterizing the type of recreational episode includes in-home, out-of-home, and pure recreational episodes (pure recreation refers to recreation trips pursued for the sole purpose of the recreational value obtained from the trip, such as walking, bicycling, and joy driving). The paper estimates a mixed multinomial logit formulation using the 2000 San Francisco Bay Area Travel Survey. The effects of household and individual sociodemographics, land-use and density variables, and episode participation attributes are examined. Inter-individual and intra-individual variation in unobserved determinants of episode type choice are also analyzed. Finally, the implications of the results for land-use and transportation planning are identified. }
}
@article{Bhat200439,
title = {Intershopping duration: an analysis using multiweek data },
journal = {Transportation Research Part B: Methodological },
volume = {38},
number = {1},
pages = {39 - 60},
year = {2004},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/S0191-2615(02)00093-0},
url = {http://www.sciencedirect.com/science/article/pii/S0191261502000930},
author = {Chandra R. Bhat and Teresa Frusti and Huimin Zhao and Stefan Schönfelder and Kay W. Axhausen},
keywords = {Multiday analysis},
keywords = {Activity–travel behavior},
keywords = {Intershopping duration},
keywords = {Latent segmentation},
keywords = {Hazard-based duration model},
keywords = {Unobserved heterogeneity },
abstract = {This study examines the rhythms in the shopping activity participation of individuals over a multiweek period by modeling the duration between successive shopping participations. A hazard-based duration model is used to model intershopping duration, and a latent segmentation method is applied to distinguish between erratic shoppers and regular shoppers. The paper applies the methodology to examine the regularity and frequency of shopping behavior of individuals using a continuous six-week travel survey collected in the cities of Halle and Karlsruhe in Germany in the fall of 1999. The empirical results underscore the need to adopt a flexible hazard model form for analyzing intershopping durations. The results also provide important insights into the determinants of the regularity and frequency of individuals’ shopping activity participation behavior. }
}
@article{Bhat2006827,
title = {A joint model for the perfect and imperfect substitute goods case: Application to activity time-use decisions },
journal = {Transportation Research Part B: Methodological },
volume = {40},
number = {10},
pages = {827 - 850},
year = {2006},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/j.trb.2005.08.004},
url = {http://www.sciencedirect.com/science/article/pii/S0191261505001098},
author = {Chandra R. Bhat and Sivaramakrishnan Srinivasan and Sudeshna Sen},
keywords = {Multiple discrete-continuous extreme value (MDCEV) model},
keywords = {Time-use},
keywords = {Mixed models},
keywords = {Weekend activity patterns},
keywords = {Built environment },
abstract = {This paper formulates a model for the joint analysis of the imperfect and perfect substitute goods case. That is, it enables the modeling of choice situations where consumers choose multiple alternatives at the same time from a certain set of alternatives, but also choose only one alternative from among a subset of alternatives. For example, in the context of time-use in leisure activity, individuals may participate in combinations of social, out-of-home recreation, and out-of-home non-maintenance shopping pursuits. These three activity types are imperfect substitutes in that they serve different functional needs of individuals and households. However, if an individual participates in out-of-home recreation, s/he may participate in only one of physically passive activities (for example, going to the movies), partially physically active activities (going to the beach or participating in spectator sports), or physically active activities (for example, working out at a gym) during a given time period (such as a weekday or a weekend day). To our knowledge, this paper is the first to consider a unified utility-maximizing framework for the analysis of such a joint imperfect–perfect substitute goods case in the economic literature. The model formulated in the paper is applied to the time-use decisions of individuals. Specifically, individual time-use in maintenance and leisure activities are modeled as a function of demographic variables, urban environment attributes, and day of week/season effects. The results from the model can be used to examine time-use choices across different segments of the population (for example, male vs. female, young vs. old, etc.), as well as to assess the potential impact of urban form policies on individual time-use decisions. }
}
@article{Bhat2005797,
title = {An analysis of multiple interepisode durations using a unifying multivariate hazard model },
journal = {Transportation Research Part B: Methodological },
volume = {39},
number = {9},
pages = {797 - 823},
year = {2005},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/j.trb.2004.11.002},
url = {http://www.sciencedirect.com/science/article/pii/S0191261504001584},
author = {Chandra R. Bhat and Sivaramakrishnan Srinivasan and Kay W. Axhausen},
abstract = {This paper jointly examines the length between successive participations in several activity purposes using a 1999 multi-week travel survey conducted in the German cities of Halle and Karlsruhe. A multivariate hazard model that accommodates a flexible duration dynamics structure, recognizes the effects of covariates, incorporates the variation in interepisode duration due to unobserved individual-specific factors and variation in interepisode duration within spells of the same individual, and considers the joint nature of participation in the various activities is proposed and applied. The variables considered in the analysis include demographics, access to the internet, location characteristics, and day of week variables. The results indicate a very distinct weekly rhythm in individuals’ participation in social, recreation, and personal business activities. While there is a similar rhythm even for participation in shopping activities, it is not as pronounced as for the non-shopping activity purposes. Also, individuals and spouse attributes, household characteristics, residential location and trip-making variables, and day of week effects have a strong influence on interepisode durations. }
}
@article{Bhat1999495,
title = {An analysis of evening commute stop-making behavior using repeated choice observations from a multi-day survey },
journal = {Transportation Research Part B: Methodological },
volume = {33},
number = {7},
pages = {495 - 510},
year = {1999},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/S0191-2615(99)00003-X},
url = {http://www.sciencedirect.com/science/article/pii/S019126159900003X},
author = {Chandra Bhat},
keywords = {Ordered-response logit},
keywords = {Unobserved heterogeneity},
keywords = {Random-coefficients},
keywords = {Heteroscedasticity},
keywords = {Maximum simulated likelihood method},
keywords = {Transportation control measures },
abstract = {This paper examines the number of stops made by individuals during their evening commute. The paper applies a methodological framework that relates stop-making to relevant individual, land-use, and work-related characteristics. The framework also accommodates unobserved variation in stop-making propensity across individuals in intrinsic preferences and in responsiveness to work-related attributes. The empirical analysis uses a sample of repeated choice observations from a multi-day sample of workers drawn from the 1990 San Francisco Bay Area Household Survey. The results indicate that the proposed model provides a superior data fit relative to a model that ignores unobserved variations in stop-making propensity across individuals. The model in this paper also provides important behavioral insights which are masked by the model that disregards unobserved variations. }
}
@article{Bhat2000567,
title = {A multi-level cross-classified model for discrete response variables },
journal = {Transportation Research Part B: Methodological },
volume = {34},
number = {7},
pages = {567 - 582},
year = {2000},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/S0191-2615(99)00038-7},
url = {http://www.sciencedirect.com/science/article/pii/S0191261599000387},
author = {Chandra R. Bhat},
keywords = {Mixed logit model},
keywords = {Multi-level analysis},
keywords = {Spatial analysis},
keywords = {Quasi-Monte Carlo sequences},
keywords = {Data clustering},
keywords = {Gaussian quadrature},
keywords = {Simulation-based econometric estimation},
keywords = {Travel mode choice modeling },
abstract = {In many spatial analysis contexts, the variable of interest is discrete and there is spatial clustering of observations. This paper formulates a model that accommodates clustering along more than one dimension in the context of a discrete response variable. For example, in a travel mode choice context, individuals are clustered by both the home zone in which they live as well as by their work locations. The model formulation takes the form of a mixed logit structure and is estimated by maximum likelihood using a combination of Gaussian quadrature and quasi-Monte Carlo simulation techniques. An application to travel mode choice suggests that ignoring the spatial context in which individuals make mode choice decisions can lead to an inferior data fit as well as provide inconsistent evaluations of transportation policy measures. }
}
@article{Bhat2003837,
title = {Simulation estimation of mixed discrete choice models using randomized and scrambled Halton sequences },
journal = {Transportation Research Part B: Methodological },
volume = {37},
number = {9},
pages = {837 - 855},
year = {2003},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/S0191-2615(02)00090-5},
url = {http://www.sciencedirect.com/science/article/pii/S0191261502000905},
author = {Chandra R. Bhat},
keywords = {Maximum simulated likelihood estimation},
keywords = {Pseudo-random sequences},
keywords = {Quasi-random sequences},
keywords = {Hybrid sequences},
keywords = {Multinomial probit model},
keywords = {Mixed logit model},
keywords = {Mixed probit model },
abstract = {The use of simulation techniques has been increasing in recent years in the transportation and related fields to accommodate flexible and behaviorally realistic structures for analysis of decision processes. This paper proposes a randomized and scrambled version of the Halton sequence for use in simulation estimation of discrete choice models. The scrambling of the Halton sequence is motivated by the rapid deterioration of the standard Halton sequence’s coverage of the integration domain in high dimensions of integration. The randomization of the sequence is motivated from a need to statistically compute the simulation variance of model parameters. The resulting hybrid sequence combines the good coverage property of quasi-Monte Carlo sequences with the ease of estimating simulation error using traditional Monte Carlo methods. The paper develops an evaluation framework for assessing the performance of the traditional pseudo-random sequence, the standard Halton sequence, and the scrambled Halton sequence. The results of computational experiments indicate that the scrambled Halton sequence performs better than the standard Halton sequence and the traditional pseudo-random sequence for simulation estimation of models with high dimensionality of integration. }
}
@article{Bhat2003857,
title = {An analysis of the impact of information and communication technologies on non-maintenance shopping activities },
journal = {Transportation Research Part B: Methodological },
volume = {37},
number = {10},
pages = {857 - 881},
year = {2003},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/S0191-2615(02)00062-0},
url = {http://www.sciencedirect.com/science/article/pii/S0191261502000620},
author = {Chandra R. Bhat and Aruna Sivakumar and Kay W. Axhausen},
keywords = {Information and communication technologies},
keywords = {Sample selection},
keywords = {Random coefficients},
keywords = {Unobserved heterogeneity},
keywords = {Hazard-based duration model},
keywords = {Multiday analysis},
keywords = {Activity–travel behavior},
keywords = {Shopping behavior },
abstract = {This paper examines the use and travel impacts of two forms of information and communication technologies (ICTs): mobile telephones and computers. The travel impacts are examined in the context of participation in out-of-home non-maintenance shopping activities over a multiweek period through the modeling of the duration between successive shopping activity participations. The empirical analysis uses a continuous six-week travel survey collected in the cities of Halle and Karlsruhe in Germany in the Fall of 1999. The results indicate that the effects of \{ICTs\} on activity–travel patterns are mediated by individual sociodemographic and locational factors, as well as by unobserved individual characteristics. The results also show that the substitution between mobile phone use and shopping travel is grossly underestimated if the effects of common unobserved factors affecting mobile phone use and shopping travel are not considered. In addition, there is quite substantial intra-individual variation in intershopping duration. }
}
@article{Bhat2005679,
title = {A multiple discrete–continuous extreme value model: formulation and application to discretionary time-use decisions },
journal = {Transportation Research Part B: Methodological },
volume = {39},
number = {8},
pages = {679 - 707},
year = {2005},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/j.trb.2004.08.003},
url = {http://www.sciencedirect.com/science/article/pii/S0191261504001274},
author = {Chandra R. Bhat},
abstract = {Several consumer demand choices are characterized by the choice of multiple alternatives simultaneously. An example of such a choice situation in activity-travel analysis is the type of discretionary (or leisure) activity to participate in and the duration of time investment of the participation. In this context, within a given temporal period (say a day or a week), an individual may decide to participate in multiple types of activities (for example, in-home social activities, out-of-home social activities, in-home recreational activities, out-of-home recreational activities, and out-of-home non-maintenance shopping activities). In this paper, we derive and formulate a utility theory-based model for discrete/continuous choice that assumes diminishing marginal utility as the level of consumption of any particular alternative increases (i.e., satiation). This assumption yields a multiple discreteness model (i.e., choice of multiple alternatives can occur simultaneously). This is in contrast to the standard discrete choice model that is based on assuming the absence of any diminishing marginal utility as the level of consumption of any alternative increases (i.e., no satiation), leading to the case of strictly single discreteness. The econometric model formulated here, which we refer to as the multiple discrete–continuous extreme value (MDCEV) model, has a surprisingly simple and elegant closed form expression for the discrete–continuous probability of not consuming certain alternatives and consuming given levels of the remaining alternatives. To our knowledge, we are the first to develop such a simple and powerful closed-form model for multiple discreteness in the literature. This formulation should constitute an important milestone in the area of multiple discreteness, just as the multinomial logit (MNL) represented an important milestone in the area of single discreteness. Further, the \{MDCEV\} model formulated here has the appealing property that it collapses to the familiar multinomial logit (MNL) choice model in the case of single discreteness. Finally, heteroscedasticity and/or correlation in unobserved characteristics affecting the demand of different alternatives can be easily incorporated within the \{MDCEV\} model framework using a mixing approach. The \{MDCEV\} model and its mixed variant are applied to analyze time-use allocation decisions among a variety of discretionary activities on weekends using data from the 2000 San Francisco Bay Area survey. }
}
@article{Bhat2002207,
title = {A continuous-time model of departure time choice for urban shopping trips },
journal = {Transportation Research Part B: Methodological },
volume = {36},
number = {3},
pages = {207 - 224},
year = {2002},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/S0191-2615(00)00047-3},
url = {http://www.sciencedirect.com/science/article/pii/S0191261500000473},
author = {Chandra R. Bhat and Jennifer L. Steed},
abstract = {This paper proposes a continuous-time hazard duration model for urban shopping trip departure time choice. The time frame for the analysis of departure time is the entire day. The continuous-time model uses a non-parametric baseline hazard distribution, employs a non-parametric representation for the time-varying effect of covariates, and accommodates time-varying covariates. These econometric issues are important to recognize and consider in a departure time model spanning the entire day. The model also accommodates unobserved heterogeneity and recognizes the “rounding” of reported departure times by individuals in surveys to an integral multiple of 5 min. The continuous-time model is estimated using shopping trip data from the 1996 activity survey collected in the Dallas-Fort Worth metropolitan area. The effects of individual and household socio-demographics, employment attributes, and trip-related characteristics on departure time choice are presented and discussed. Application of the continuous-time model to forecast temporal shifts in shopping trip-making due to changes in socio-demographic characteristics and trip-chaining behavior is demonstrated. The use of the formulation as a powerful evaluation tool to manage and influence traffic patterns through dynamic congestion pricing control schemes is also highlighted. }
}
@article{Guo200731,
title = {Operationalizing the concept of neighborhood: Application to residential location choice analysis },
journal = {Journal of Transport Geography },
volume = {15},
number = {1},
pages = {31 - 45},
year = {2007},
note = {},
issn = {0966-6923},
doi = {http://dx.doi.org/10.1016/j.jtrangeo.2005.11.001},
url = {http://www.sciencedirect.com/science/article/pii/S096669230500089X},
author = {Jessica Y. Guo and Chandra R. Bhat},
keywords = {Neighborhood},
keywords = {Spatial definition},
keywords = {Residential location choice},
keywords = {Modifiable areal unit problem },
abstract = {In this paper, we explore different conceptualizations to represent neighborhoods in residential location choice models, and describe three alternative ways for constructing operational units to represent neighborhoods. In particular, we examine the possibility of using the census units to represent the hierarchical ‘fixed neighborhood’ definition, and the circular units and network bands to represent the hierarchical ‘sliding neighborhood’ definition. Overall, the network band definition is conceptually appealing. It also is marginally superior to the other two operational representations from a model fit standpoint. }
}
@article{Bhat2006709,
title = {The impact of stop-making and travel time reliability on commute mode choice },
journal = {Transportation Research Part B: Methodological },
volume = {40},
number = {9},
pages = {709 - 730},
year = {2006},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/j.trb.2005.09.008},
url = {http://www.sciencedirect.com/science/article/pii/S0191261505001086},
author = {Chandra R. Bhat and Rupali Sardesai},
keywords = {Travel time reliability},
keywords = {Mixed logit},
keywords = {Activity-based analysis},
keywords = {Commute travel},
keywords = {Mode choice},
keywords = {Revealed preference–stated preference modeling },
abstract = {This paper uses revealed preference and stated preference data collected from a web-based commuter survey in Austin, Texas, to estimate a commute mode choice model. This model accommodates weekly and daily commute and midday stop-making behavior, as well as travel time reliability. A mixed logit framework is used in estimation. The results emphasize the effects of commute and midday stop-making on commute mode choice. The results also indicate that travel time reliability is an important variable in commute mode choice decisions. The paper applies the estimated model to predict the potential mode usage of a proposed commuter rail option as well as to examine the impact of highway tolls. More generally, the mode choice model can be used to examine a whole range of travel mode-related policy actions for the Austin metropolitan region. }
}
@article{Bhat2001677,
title = {Quasi-random maximum simulated likelihood estimation of the mixed multinomial logit model },
journal = {Transportation Research Part B: Methodological },
volume = {35},
number = {7},
pages = {677 - 693},
year = {2001},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/S0191-2615(00)00014-X},
url = {http://www.sciencedirect.com/science/article/pii/S019126150000014X},
author = {Chandra R. Bhat},
keywords = {Mixed multinomial logit model},
keywords = {Maximum simulated likelihood estimation},
keywords = {Pseudo-random sequences},
keywords = {Quasi-random sequences},
keywords = {Polynomial-based cubature},
keywords = {Discrete choice analysis },
abstract = {This paper proposes the use of a quasi-random sequence for the estimation of the mixed multinomial logit model. The mixed multinomial structure is a flexible discrete choice formulation which accommodates general patterns of competitiveness as well as heterogeneity across individuals in sensitivity to exogenous variables. The estimation of this model has been achieved in the past using the pseudo-random maximum simulated likelihood method that evaluates the multi-dimensional integrals in the log-likelihood function by computing the integrand at a sequence of pseudo-random points and taking the average of the resulting integrand values. We suggest and implement an alternative quasi-random maximum simulated likelihood method which uses cleverly crafted non-random but more uniformly distributed sequences in place of the pseudo-random points in the estimation of the mixed logit model. Numerical experiments, in the context of intercity travel mode choice, indicate that the quasi-random method provides considerably better accuracy with much fewer draws and computational time than does the pseudo-random method. This result has the potential to dramatically influence the use of the mixed logit model in practice; specifically, given the flexibility of the mixed logit model, the use of the quasi-random estimation method should facilitate the application of behaviorally rich structures in discrete choice modeling. }
}
@article{Bhat2004147,
title = {A mixed spatially correlated logit model: formulation and application to residential choice modeling },
journal = {Transportation Research Part B: Methodological },
volume = {38},
number = {2},
pages = {147 - 168},
year = {2004},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/S0191-2615(03)00005-5},
url = {http://www.sciencedirect.com/science/article/pii/S0191261503000055},
author = {Chandra R. Bhat and Jessica Guo},
abstract = {In recent years, there have been important developments in the simulation analysis of the mixed multinomial logit model as well as in the formulation of increasingly flexible closed-form models belonging to the generalized extreme value class. In this paper, we bring these developments together to propose a mixed spatially correlated logit (MSCL) model for location-related choices. The \{MSCL\} model represents a powerful approach to capture both random taste variations as well as spatial correlation in location choice analysis. The \{MSCL\} model is applied to an analysis of residential location choice using data drawn from the 1996 Dallas–Fort Worth household survey. The empirical results underscore the need to capture unobserved taste variations and spatial correlation, both for improved data fit and the realistic assessment of the effect of sociodemographic, transportation system, and land-use changes on residential location choice. }
}
@article{Bhat200635,
title = {Household vehicle type holdings and usage: an application of the multiple discrete-continuous extreme value (MDCEV) model },
journal = {Transportation Research Part B: Methodological },
volume = {40},
number = {1},
pages = {35 - 53},
year = {2006},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/j.trb.2005.01.003},
url = {http://www.sciencedirect.com/science/article/pii/S0191261505000093},
author = {Chandra R. Bhat and Sudeshna Sen},
abstract = {The increasing diversity of vehicle type holdings and the growing usage of vehicles by households have serious policy implications for traffic congestion and air pollution. Consequently, it is important to accurately predict the vehicle holdings of households as well as the vehicle miles of travel by vehicle type to project future traffic congestion and mobile source emission levels. In this paper, we apply a multiple discrete-continuous extreme value model to analyze the holdings and use of multiple vehicle types by households. Data for the analysis is drawn from a 2000 San Francisco Bay Area survey. The model results indicate the important effects of household demographics, residence location variables and vehicle attributes on vehicle type holdings and use. The model developed in the paper can be applied to predict the impact of demographic, land use, and operating cost changes on vehicle type holdings and usage. Such predictions are important at a time when the household demographic characteristics are changing rapidly in the United States. The predictions can also inform the design of proactive land-use, economic, and transportation policies to influence household vehicle holdings and usage in a way that reduces traffic congestion and air quality problems. }
}
@article{Bhat2002593,
title = {A unified mixed logit framework for modeling revealed and stated preferences: formulation and application to congestion pricing analysis in the San Francisco Bay area },
journal = {Transportation Research Part B: Methodological },
volume = {36},
number = {7},
pages = {593 - 616},
year = {2002},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/S0191-2615(01)00020-0},
url = {http://www.sciencedirect.com/science/article/pii/S0191261501000200},
author = {Chandra R. Bhat and Saul Castelar},
keywords = {Revealed preference},
keywords = {Stated preference},
keywords = {Mixed logit},
keywords = {Quasi-Monte Carlo simulation},
keywords = {State-dependence},
keywords = {Unobserved heterogeneity},
keywords = {Congestion pricing },
abstract = {This paper formulates and applies a unified mixed-logit framework for joint analysis of revealed and stated preference data that accommodates a flexible competition pattern across alternatives, scale difference in the revealed and stated choice contexts, heterogeneity across individuals in the intrinsic preferences for alternatives, heterogeneity across individuals in the responsiveness to level-of-service factors, state-dependence of the stated choices on the revealed choice, and heterogeneity across individuals in the state-dependence effect. The estimation of the mixed logit formulation is achieved using simulation techniques that employ quasi-random Monte Carlo draws. The formulation is applied to examine the travel behavior responses of San Francisco Bay Bridge users to changes in travel conditions. The data for the study are drawn from surveys conducted as part of the 1996 San Francisco Bay Area Travel Study. The results of the mixed logit formulation are compared with those of more restrictive structures on the basis of parameter estimates, implied trade-offs among level-of-service attributes, heterogeneity and state-dependence effects, data fit, and substantive implications of congestion pricing policy simulations. }
}
@article{Bhat1998455,
title = {Accommodating flexible substitution patterns in multi-dimensional choice modeling: formulation and application to travel mode and departure time choice },
journal = {Transportation Research Part B: Methodological },
volume = {32},
number = {7},
pages = {455 - 466},
year = {1998},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/S0191-2615(98)00011-3},
url = {http://www.sciencedirect.com/science/article/pii/S0191261598000113},
author = {Chandra R. Bhat},
keywords = {nested logit model},
keywords = {error-components logit},
keywords = {mixed multinomial logit},
keywords = {simulation estimation technique},
keywords = {nonwork trip modeling},
keywords = {travel mode choice modeling},
keywords = {departure time analysis },
abstract = {The nested logit model has been used extensively to model multi-dimensional choice situations. A drawback of the nested logit model is that it does not allow choice alternatives to share common unobserved attributes along all the dimensions characterizing the multidimensional choice context. This paper formulates a mixed multinomial logit structure that accommodates unobserved correlation across both dimensions in a two-dimensional choice context. The mixed multinomial logit structure is parsimonious in the number of parameters to be estimated and is also relatively easy to estimate using simulation methods. The mixed multinomial logit model is applied to an analysis of travel mode and departure time choice for home-based social–recreational trips using data drawn from the 1990 San Francisco Bay Area household survey. The empirical results underscore the need to capture unobserved attributes along both the mode and departure time dimensions, both for improved data fit as well as for more realistic policy evaluations of transportation control measures. }
}
@article{Bhat1993265,
title = {Driver recruitability for advanced traveler information system experiments },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {1},
number = {4},
pages = {265 - 274},
year = {1993},
note = {},
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/0968-090X(93)90001-V},
url = {http://www.sciencedirect.com/science/article/pii/0968090X9390001V},
author = {Chandra R. Bhat and Joseph L. Schofer and Frank S. Koppelman and Russell C. Bautch},
abstract = {A number of Advanced Traveler Information System (ATIS) field experiments are being undertaken to study the effectiveness of the \{ATIS\} concept in ameliorating traffic congestion and reducing delays. Many of these experiments require the participation of private drivers willing to allow in-vehicle navigation units to be installed in their vehicles over an extended period of time. A critical part of any \{ATIS\} field experiment is the selection or recruitment of private drivers to fulfill the multi-purpose participation needs of the \{ATIS\} experiment. To provide an informed basis for designing such a driver recruitment effort, it is important to understand the factors affecting driver recruitability or “willingness to participate.” This research presents the results of a quantitative analysis of driver recruitability conducted to aid in the design of recruitment procedures for \{ADVANCE\} (Advanced Driver and Vehicle Advisory Navigation Concept), the largest \{ATIS\} field experiment of its kind. The approach used a telephone survey to assess driver willingness to participate in the \{ADVANCE\} field experiment and to explore variations in that willingness among different drivers and across characteristics of the \{ADVANCE\} system and experimental design. The results indicate that the willingness to participate in the \{ADVANCE\} field test is greater for men, persons who hold executive or managerial occupations, individuals who drive extensively, persons who use electronic devices such as personal computers and car phones regularly, and persons who have positive beliefs regarding the usefulness of the \{ADVANCE\} concept. The result also suggest that drivers' willingness to participate is not strongly affected by monitoring/reporting requirements such as responding to surveys, mailing electronically stored records of system operation, and periodic service requirements. However, the willingness decreases considerably if drivers have to bear the financial responsibility for damage of the navigation equipment and any equipment-caused electrical failures to the car. Finally, the incentive of a lottery prize raises the level of participation willingness. These results have important implications for the recruitment effort, both in terms of recruiting drivers for participation in the demonstration and specifying the operational details of the field test. }
}
@article{Bhat1998361,
title = {Analysis of travel mode and departure time choice for urban shopping trips },
journal = {Transportation Research Part B: Methodological },
volume = {32},
number = {6},
pages = {361 - 371},
year = {1998},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/S0191-2615(98)00004-6},
url = {http://www.sciencedirect.com/science/article/pii/S0191261598000046},
author = {Chandra R Bhat},
keywords = {generalized extreme-value model},
keywords = {nonwork trips},
keywords = {congestion pricing},
keywords = {peak period pricing},
keywords = {traffic congestion },
abstract = {Travel mode and departure time choice of urban trips are important determinants of urban travel demand and the temporal distribution of this demand. While mode choice has received substantial attention in travel demand modeling, relatively little attention has been directed toward departure time choice. Further, the work trip has been the focus of most earlier mode choice research, and almost all earlier departure time choice research. The current paper examines the joint nature of mode and departure time choice for urban shopping trips. The model formulation in the paper adopts a nested structure with mode choice at the higher level of the hierarchy and departure time choice at the lower level. A multinomial logit (MNL) form is used for modeling mode choice and an ordered generalized extreme value (OGEV) form, which recognizes the natural temporal ordering of the departure time alternatives, is adopted for departure time choice. The proposed MNL-OGEV model is applied to data obtained from the 1990 San Francisco Bay area travel survey and is found to perform better than the \{MNL\} and nested logit models. In addition, the results indicate that the \{MNL\} and nested logit models lead to biased level-of-service estimates and to inappropriate policy evaluations of transportation control measures in the current empirical context. }
}
@article{Ramamohan1994273,
title = {Chaotic dynamics of a periodically forced slender body in a simple shear flow },
journal = {Physics Letters A },
volume = {190},
number = {3–4},
pages = {273 - 278},
year = {1994},
note = {},
issn = {0375-9601},
doi = {http://dx.doi.org/10.1016/0375-9601(94)90754-4},
url = {http://www.sciencedirect.com/science/article/pii/0375960194907544},
author = {T.R. Ramamohan and S. Savithri and R. Sreenivasan and C.Chandra Shekara Bhat},
abstract = {The dynamics of a periodically forced slender body in a simple shear flow is analysed. This represents the simplest case of a class of problems that have not attracted attention in the literature. The system undergoes a quasiperiodic transition to chaos in the range of parameters investigated. It also exhibits chaotic transients obtained by the apparent collision of a stable nonchaotic attractor and a chaotic attractor with the transients scaling in a manner similar to that analysed by Grebogi et al. [Ergodic Theory Dynamical Systems 5 (1985) 341] with the exponent of scaling approximately equal to -0.5. The class of problems to which this paper is an introduction is technologically important and can lead to new methods of processing composites, electrorheological fluids and polymer solutions. }
}
@article{Bhat1998387,
title = {A model of post home-arrival activity participation behavior },
journal = {Transportation Research Part B: Methodological },
volume = {32},
number = {6},
pages = {387 - 400},
year = {1998},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/S0191-2615(98)00006-X},
url = {http://www.sciencedirect.com/science/article/pii/S019126159800006X},
author = {Chandra R. Bhat},
keywords = {activity-based travel analysis},
keywords = {discrete-continuous econometric model},
keywords = {activity type modeling},
keywords = {activity duration},
keywords = {home-stay duration },
abstract = {The research presented here develops a methodology to jointly model travelers’ activity-type choice for participation, home-stay duration before participation in an out-of-home activity and out-of-home activity duration of participation. The paper applies the methodology to examine travelers’ activity behavior after returning home at the end of the work tour using data from a Boston region household activity survey. The empirical results underscore the importance of accommodating the inter-relationships among different elements of an individual’s activity behavior. The results also provide important insights into the determinants of travelers’ post home-arrival activity participation behavior. }
}
@article{Koppelman1993383,
title = {Market research evaluation of actions to reduce suburban traffic congestion: Commuter travel behavior and response to demand reduction actions },
journal = {Transportation Research Part A: Policy and Practice },
volume = {27},
number = {5},
pages = {383 - 393},
year = {1993},
note = {},
issn = {0965-8564},
doi = {http://dx.doi.org/10.1016/0965-8564(93)90034-I},
url = {http://www.sciencedirect.com/science/article/pii/096585649390034I},
author = {Frank S. Koppelman and Chandra R. Bhat and Joseph L. Schofer},
abstract = {This research paper is directed toward obtaining a better understanding of current work trip mode choice of commuters in suburban areas and the effectiveness of alternate demand reduction actions in alleviating congestion, based on a Chicago area study. The paper is particularly concerned with an evaluation of the effectiveness of demand reduction actions that encourage the use of ridesharing modes (carpool, vanpool and transit) and/or discourage the use of drive-alone auto for the work trip. A conceptual framework of current mode-choice behavior and behavioral response to demand reduction actions is developed. The empirical analysis suggests that in the midwest suburban setting, any substantial increase in ridesharing propensity appears to require a combination of ridesharing incentives in the form of improved service characteristics and direct auto-use disincentives in the form of substantially increased parking costs. Our analysis also suggests that ridesharing propensity is greater for women and individuals in households with fewer autos. Individuals who have a great need for independence, make additional trips on their way to and from work, frequently stay late at work, and have a high income tend to be less inclined to use ridesharing modes. }
}
@article{Bhat1993433,
title = {A conceptual framework of individual activity program generation },
journal = {Transportation Research Part A: Policy and Practice },
volume = {27},
number = {6},
pages = {433 - 446},
year = {1993},
note = {},
issn = {0965-8564},
doi = {http://dx.doi.org/10.1016/0965-8564(93)90050-U},
url = {http://www.sciencedirect.com/science/article/pii/096585649390050U},
author = {Chandra R. Bhat and Frank S. Koppelman},
abstract = {The research in this paper attempts to better understand the process by which activities are generated at an individual level. Activity-based travel analyses have gained popularity in recent years because they recognize the complexity of activity behavior and view travel as a derivative of this behavior. Most activity-based studies have focused on the spatial and temporal linkage of trips; that is, the scheduling of activities. They consider the agenda of activities for participation, and associated attributes of the activity participation (such as mode to activity and location of activity performance), as predetermined. This paper develops a comprehensive conceptual framework of the relatively unexplored area of activity agenda generation. Such a framework will be valuable in empirical modeling of activity generation behavior. A subsequent paper focuses on translating a part of this conceptual framework into an empirical model. }
}
@article{Bhat1993447,
title = {An endogenous switching simultaneous equation system of employment, income, and car ownership },
journal = {Transportation Research Part A: Policy and Practice },
volume = {27},
number = {6},
pages = {447 - 459},
year = {1993},
note = {},
issn = {0965-8564},
doi = {http://dx.doi.org/10.1016/0965-8564(93)90051-L},
url = {http://www.sciencedirect.com/science/article/pii/096585649390051L},
author = {Chandra R. Bhat and Frank S. Koppelman},
abstract = {The research presented here makes an advance toward the inclusion of employment and income within a transportation framework based on the conceptual framework developed by the authors in a preceding paper. Employment and income are important determinants of travel behavior. They have been used as exogenous variables in travel forecasting models such as trip generation models, car ownership models and mode choice models. This paper proposes a fundamental change in the current view of employment and income as exogenous variables in travel demand models. In particular, we emphasize the need, both from a forecasting and estimation point of view, to include employment and income as endogenous variables within a disaggregate travel demand modeling framework. The paper formulates and estimates an integrated model of employment, income and car ownership, which takes account of interdependencies among these variables and their structural relationships with relevant exogenous variables. }
}
@article{Bhat199711,
title = {Covariance heterogeneity in nested logit models: Econometric structure and application to intercity travel },
journal = {Transportation Research Part B: Methodological },
volume = {31},
number = {1},
pages = {11 - 21},
year = {1997},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/S0191-2615(96)00018-5},
url = {http://www.sciencedirect.com/science/article/pii/S0191261596000185},
author = {Chandra R. Bhat},
abstract = {The nested logit model relaxes the ‘independence of irrelevant alternatives’ (IIA) property of the multinomial logit model by grouping alternatives based on their degree of substitution. Alternatives in a nest exhibit an identical degree of increased sensitivity relative to alternatives not in the nest. An assumption maintained in the nested logit is that the degree of sensitivity among nested alternatives is invariant across agents making the choice. This assumption might be untenable in many situations. In this paper, we propose an extension of the nested logit model to allow heterogeneity (across agents) in the covariance among nested alternatives based on observed agent characteristics. We label this model as the \{COVNL\} model. The multinomial logit, the nested logit, and the \{COVNL\} model are estimated to examine the impact of improved rail service on weekday, business travel in the Toronto-Montreal corridor. The empirical results show that not accounting for covariance heterogeneity in the nested logit formulation leads to a statistically inferior data fit and also to biased model estimates of the effects of level-of-service variables. }
}
@article{Bhat1996189,
title = {A hazard-based duration model of shopping activity with nonparametric baseline specification and nonparametric control for unobserved heterogeneity },
journal = {Transportation Research Part B: Methodological },
volume = {30},
number = {3},
pages = {189 - 207},
year = {1996},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/0191-2615(95)00029-1},
url = {http://www.sciencedirect.com/science/article/pii/0191261595000291},
author = {Chandra R. Bhat},
abstract = {Activity duration is an important component of the activity participation behavior of individuals, and therefore, an important determinant of individual travel behavior. In this paper, we examine the factors affecting shopping activity duration during the return home from work and develop a comprehensive methodological framework to estimate a stochastic hazard-based duration model from grouped (interval-level) failure data. The framework accommodates a nonparametric baseline hazard distribution and allows for nonparametric control of unobserved heterogeneity, while incorporating the effects of covariates. The framework also facilitates statistical testing of alternative parametric assumptions on the baseline hazard distribution and on the unobserved heterogeneity distribution. Our empirical results indicate significant effects of unobserved heterogeneity on shopping activity duration of individuals. Further, we find that parametric forms for the baseline hazard and unobserved heterogeneity distributions are inadequate, and are likely to lead to substantial biases in covariate effects and hazard dynamics. The empirical results also provide insights into the determinants of shopping activity duration during the commute trip. }
}
@article{Bhat1998495,
title = {Accommodating variations in responsiveness to level-of-service measures in travel mode choice modeling },
journal = {Transportation Research Part A: Policy and Practice },
volume = {32},
number = {7},
pages = {495 - 507},
year = {1998},
note = {},
issn = {0965-8564},
doi = {http://dx.doi.org/10.1016/S0965-8564(98)00011-1},
url = {http://www.sciencedirect.com/science/article/pii/S0965856498000111},
author = {Chandra R. Bhat},
keywords = {intercity travel},
keywords = {maximum simulated likelihood function},
keywords = {multinomial logit model},
keywords = {taste heterogeneity},
keywords = {random-coefficients. },
abstract = {An individual’s responsiveness to level-of-service variables affects her or his travel mode choice for a trip. This responsiveness will, in general, vary across individuals based on observed (to an analyst) and unobserved (to an analyst) individual characteristics. The current paper formulates a multinomial-logit based model of travel mode choice that accommodates variations in responsiveness to level-of-service measures due to both observed and unobserved individual characteristics in a comprehensive manner. The choice probabilities in the resulting model are evaluated using Monte Carlo simulation techniques and the model parameters are estimated using a maximum simulated likelihood approach. The model is applied to examine the impact of improved rail service on weekday, business travel in the Toronto—Montreal corridor. The empirical results show that not accounting adequately for variations in responsiveness across individuals leads to a statistically inferior data fit and also to inappropriate evaluations of policy actions aimed at improving inter-city transportation services. }
}
@article{Bhat1994311,
title = {Imputing a continuous income variable from grouped and missing income observations },
journal = {Economics Letters },
volume = {46},
number = {4},
pages = {311 - 319},
year = {1994},
note = {},
issn = {0165-1765},
doi = {http://dx.doi.org/10.1016/0165-1765(94)90151-1},
url = {http://www.sciencedirect.com/science/article/pii/0165176594901511},
author = {Chandra R. Bhat},
abstract = {Most cross-sectional data sets collect income in a discrete number of categories (that is, in grouped form) to simplify the respondent's task and to encourage a response. In spite of such grouped data collection, many respondents refuse to provide information on income. This paper develops a method to impute a continuous and reliable value for income from grouped and missing income data. }
}
@article{Bhat1995471,
title = {A heteroscedastic extreme value model of intercity travel mode choice },
journal = {Transportation Research Part B: Methodological },
volume = {29},
number = {6},
pages = {471 - 483},
year = {1995},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/0191-2615(95)00015-6},
url = {http://www.sciencedirect.com/science/article/pii/0191261595000156},
author = {Chandra R. Bhat},
abstract = {Estimation of disaggregate mode choice models to estimate the ridership share on a proposed new (or improved) intercity travel service and to identify the modes from which existing intercity travelers will be diverted to the new or upgraded service constitutes a critical part of evaluating alternative travel service proposals to alleviate intercity travel congestion. This paper develops a new heteroscedastic extreme value model of intercity mode choice that overcomes the ‘independence of irrelevant alternatives’ (IIA) property of the commonly used multinomial logit model. The proposed model allows a more flexible cross-elasticity structure among alternatives than the nested logit model. It is also simple, intuitive and much less of a computational burden than the multinomial probit model. The paper discusses the non-IIA property of the heteroscedastic extreme value model and presents an efficient and accurate Gaussian quadrature technique to estimate the heteroscedastic model using the maximum likelihood method. The multinomial logit, alternative nested logit structures, and the heteroscedastic model are estimated to examine the impact of improved rail service on business travel in the Toronto-Montreal corridor. The nested logit structures are either inconsistent with utility maximization principles or are not significantly better than the multinomial logit model. The heteroscedastic extreme value model, however, is found to be superior to the multinomial logit model. The heteroscedastic model predicts smaller increases in rail shares and smaller decreases in non-rail shares than the multinomial logit in response to rail-service improvements. It also suggests a larger percentage decrease in air share and a smaller percentage decrease in auto share than the multinomial logit. Thus, the multinomial logit model is likely to provide overly optimistic projections of rail ridership and revenue, and of alleviation in inter-city travel congestion in general, and highway traffic congestion in particular. These findings point to the limitations of the multinomial logit and nested logit models in studying intercity mode choice behavior and to the usefulness of the heteroscedastic model proposed in this paper. }
}
@article{Bhat199741,
title = {Work travel mode choice and number of non-work commute stops },
journal = {Transportation Research Part B: Methodological },
volume = {31},
number = {1},
pages = {41 - 54},
year = {1997},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/S0191-2615(96)00016-1},
url = {http://www.sciencedirect.com/science/article/pii/S0191261596000161},
author = {Chandra R. Bhat},
abstract = {The research presented here develops a joint model of work travel mode choice and number of stops during the work commute. This model provides an improved basis for evaluating the effect of alternative policy actions to alleviate peak-period congestion. The model also contributes to activity-based research by allowing a more realistic behavioral representation of the simultaneous disaggregate choice process underlying mode choice to work and choice of number of activity stops. Mode choice is modeled by using a multinomial logit model and the number of stops is modeled by using an ordered-response formulation. The joint model is applied to an empirical analysis using data from an activity survey conducted in the Boston Metropolitan area. The results underscore the importance of accommodating the inter-relationship between mode choice to work and number of activity stops in the work commute. The effects of a variety of congestion-alleviation measures are examined using the model. }
}
@comment{{Hassan Abdelwahab PAPERS}}
@article{Abdelwahab2014285,
title = {The reliability and reproducibility of ultrasonography for measuring the residual urine volume in men with lower urinary tract symptoms },
journal = {Arab Journal of Urology },
volume = {12},
number = {4},
pages = {285 - 289},
year = {2014},
note = {},
issn = {2090-598X},
doi = {http://dx.doi.org/10.1016/j.aju.2014.10.002},
url = {http://www.sciencedirect.com/science/article/pii/S2090598X14000990},
author = {Hassan A. Abdelwahab and Housseini M. Abdalla and Mahmoud H. Sherief and Mohamed B. Ibrahim and Mostafa A. Shamaa},
keywords = {Ultrasonography},
keywords = {Catheter},
keywords = {Postvoid residual urine volume},
keywords = {Ultrasonography },
abstract = {AbstractObjective To assess the reliability and reproducibility of abdominal ultrasonography (US) for measuring the postvoid residual urine volume (PVR), and to compare measurements by a radiologist and urologist, in men with lower urinary tract symptoms (LUTS), as a significant \{PVR\} is common in patients with \{LUTS\} and an assessment of the \{PVR\} could protect patients from unnecessary catheterisation. Patients and methods This was a prospective comparative study of 45 men aged ⩾45 years with \{LUTS\} attending a urological outpatient clinic from July 2011 to May 2012. A detailed history was taken, with an assessment of \{LUTS\} using the Arabic Validated International Prostate Symptom Score (IPSS) and complete general and local examination. The \{PVR\} was measured by \{US\} twice by a radiologist and urologist, and then repeated after 1 week. Within ⩽2 min after \{US\} a urethral catheter was used to measure the PVR. Results The mean (range) age of the patients was 63.8 (45–88) years and the mean \{IPSS\} was 16.18. Reliability testing between the \{PVR\} measured by \{US\} and the catheterised measure of \{PVR\} showed that \{US\} was not reliable (Cronbach’s α < 0.7). The \{US\} measurement was reproducible for both single examiner over two sessions, and with two examiners in one session. The \{PVR\} obtained by the urethral catheter was significantly higher than the \{US\} measurement (P < 0.05). Conclusions The measurement of \{PVR\} by \{US\} is reproducible by either a urologist or radiologist, but it is not reliable, as the urethral catheter estimate gives a significantly higher PVR. }
}
@article{ElAtrash2014234,
title = {The assessment of sexual dysfunction in Egyptian women with lower urinary tract symptoms },
journal = {Arab Journal of Urology },
volume = {12},
number = {3},
pages = {234 - 238},
year = {2014},
note = {},
issn = {2090-598X},
doi = {http://dx.doi.org/10.1016/j.aju.2014.03.002},
url = {http://www.sciencedirect.com/science/article/pii/S2090598X1400031X},
author = {Gamal El Atrash and Mohamed H. Ali and Hassan A. Abdelwahab and Lobna A. Abdelreheem and Mostafa Shamaa},
keywords = {Female sexual dysfunction},
keywords = {Lower urinary tract symptoms},
keywords = {Women },
abstract = {AbstractIntroduction Female sexual dysfunction (FSD) has been reported in 46% of women with lower urinary tract symptoms (LUTS). \{FSD\} is a common health problem that remains under-investigated, especially in Eastern communities, where discussion of the issue is considered a taboo. In this study we determined the prevalence of various subtypes of \{FSD\} in relation to \{LUTS\} in women in Ismailia, Egypt. Patients and methods This was a case-control study to assess \{FSD\} in women with \{LUTS\} in comparison to normal women. In all, 101 women patients attending the Urology clinic at our institution were divided into two groups, a study group of 52 with \{LUTS\} and a control group of 49 with no LUTS. Validated Arabic versions of the \{FSD\} index and the Bristol questionnaire were used to assess the participants, and the data analysed statistically. Results \{FSD\} was diagnosed in 75 of the 101 patients (74%); 87 (86%) reported hypoactive sexual desire, 61 (60%) reported sexual arousal disorder, 56 (55%) had lubrication disorders, 65 (64%) complained of orgasmic deficiency, 36 (36%) had satisfaction disorder, and 59 (58%) had sexual pain disorder (e.g., dyspareunia or non-coital genital pain). Arousal, satisfaction, orgasmic and lubrication disorders were more common in the women with LUTS. There was no statistically significant difference in desire disorders between the groups. Conclusions \{FSD\} and its subtypes are more prevalent in women with \{LUTS\} in this sample of Egyptian women. }
}
@article{Shaaban201424,
title = {Assessment of female sexual function among women with pelvic organ prolapse or urinary incontinence via an Arabic validated short-form sexual questionnaire },
journal = {International Journal of Gynecology & Obstetrics },
volume = {124},
number = {1},
pages = {24 - 26},
year = {2014},
note = {},
issn = {0020-7292},
doi = {http://dx.doi.org/10.1016/j.ijgo.2013.06.031},
url = {http://www.sciencedirect.com/science/article/pii/S0020729213004311},
author = {Mohamed M. Shaaban and Hassan A. Abdelwahab and Magdy R. Ahmed and Essam Shalaby},
keywords = {Pelvic organ prolapse},
keywords = {Short sexual questionnaire},
keywords = {Urinary incontinence },
abstract = {AbstractObjective To assess female sexual function among women with pelvic organ prolapse or urinary incontinence via an Arabic, validated, short-form sexual questionnaire (PISQ-12). Methods The present study was conducted among women attending Suez Canal University Hospital, Ismailia, Egypt, between September 2009 and August 2011. In the pilot study, 42 women completed the final version of the Arabic PISQ-12 at recruitment and then 2 weeks later, and the data were compared to evaluate reliability and internal consistency. The formal comparative study included 154 premenopausal sexually active women: 80 control women, and 74 women with some degree of pelvic prolapse with or without stress incontinence. All participants had a vaginal examination and completed the questionnaire. The main outcome measures were the mean questionnaire scores within its 3 domains (behavioral, physical, and partner-related). Results The test–retest reliability and internal consistency of the Arabic PISQ-12 were excellent. Validity was approved by an expert panel. The case group had a significantly lower mean total questionnaire score (31.07 ± 4.2 vs 34.7 ± 6.2; P < 0.05) but a higher partner-related score (9.0 ± 2.4 vs 8.4 ± 2.5; P < 0.05). Conclusion The Arabic version of PISQ-12 was shown to be an effective and objective method of evaluating sexual function among patients with pelvic organ prolapse. }
}
@article{Spizzirri2013115,
title = {Spherical gelatin/CNTs hybrid microgels as electro-responsive drug delivery systems },
journal = {International Journal of Pharmaceutics },
volume = {448},
number = {1},
pages = {115 - 122},
year = {2013},
note = {},
issn = {0378-5173},
doi = {http://dx.doi.org/10.1016/j.ijpharm.2013.03.013},
url = {http://www.sciencedirect.com/science/article/pii/S0378517313002329},
author = {U. Gianfranco Spizzirri and Silke Hampel and Giuseppe Cirillo and Fiore Pasquale Nicoletta and Abdelwahab Hassan and Orazio Vittorio and Nevio Picci and Francesca Iemma},
keywords = {Gelatin hydrogels},
keywords = {Electro-responsivity},
keywords = {Carbon nanotubes},
keywords = {Hybrid microspheres},
keywords = {Drug delivery },
abstract = {Abstract Novel spherical hybrid hydrogels composed of gelatin and multi-walled carbon nanotubes were synthesized by emulsion polymerization in the presence of sodium methacrylate and N,N′-ethylenebisacrylamide, and proposed as drug delivery microspheres for the electro-responsive release of Diclofenac sodium salt. Different amounts of nanotubes (up to 35% by weight) were covalently inserted into the polymeric network in order to determine the percentage conferring the highest electric sensitivity to the composite microspheres. Characterization of hydrogels was performed by electrical, morphological and calorimetric analyses, Raman measurements, biocompatibility assays and evaluation of the swelling behaviors in water (pH 1.0 and pH 7.4) with and without the application of an external electric field. Finally, the release profiles were determined and the diffusion behavior was evaluated by semi-empirical equations. }
}
@article{Abdelwahab20111190,
title = {Anti-inflammatory activities of cucurbitacin E isolated from Citrullus lanatus var. citroides: Role of reactive nitrogen species and cyclooxygenase enzyme inhibition },
journal = {Fitoterapia },
volume = {82},
number = {8},
pages = {1190 - 1197},
year = {2011},
note = {},
issn = {0367-326X},
doi = {http://dx.doi.org/10.1016/j.fitote.2011.08.002},
url = {http://www.sciencedirect.com/science/article/pii/S0367326X11001870},
author = {Siddig Ibrahim Abdelwahab and Loiy Elsir Ahmed Hassan and Hasnah Mohd Sirat and Sakina M. Ahmed Yagi and Waleed S. Koko and Syam Mohan and Manal Mohamed Elhassan Taha and Syahida Ahmad and Cheah Shiau Chuen and Putri Narrima and Mohd Mustafa Rais and A. Hamid A. Hadi},
keywords = {Cucurbitacin E},
keywords = {Wild melon},
keywords = {Cyclooxygenase enzymes: reactive nitrogen species},
keywords = {\{RAW\} 264.7 macrophage },
abstract = {The in vivo and in vitro mechanistic anti-inflammatory actions of cucurbitacin E (CE) (Citrullus lanatus var. citroides) were examined. The results showed that LPS/INF-γ increased \{NO\} production in RAW264.7 macrophages, whereas L-NAME and \{CE\} curtailed it. \{CE\} did not reveal any cytotoxicity on RAW264.7 and WRL-68 cells. \{CE\} inhibited both \{COX\} enzymes with more selectivity toward COX-2. Intraperitoneal injection of \{CE\} significantly suppressed carrageenan-induced rat's paw edema. \{ORAC\} and \{FRAP\} assays showed that \{CE\} is not a potent \{ROS\} scavenger. It could be concluded that \{CE\} is potentially useful in treating inflammation through the inhibition of \{COX\} and \{RNS\} but not ROS. }
}
@comment{{Mohamed Abdel-Aty PAPERS}}
@article{Park201580,
title = {Assessment of safety effects for widening urban roadways in developing crash modification functions using nonlinearizing link functions },
journal = {Accident Analysis & Prevention },
volume = {79},
number = {0},
pages = {80 - 87},
year = {2015},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2015.03.025},
url = {http://www.sciencedirect.com/science/article/pii/S0001457515001001},
author = {Juneyoung Park and Mohamed Abdel-Aty and Jung-Han Wang and Chris Lee},
keywords = {Safety effectiveness},
keywords = {Crash modification factors and functions},
keywords = {Bayesian regression},
keywords = {Nonlinearinzing link function},
keywords = {Observational before–after methods},
keywords = {Time changes },
abstract = {Abstract Since a crash modification factor (CMF) represents the overall safety performance of specific treatments in a single fixed value, there is a need to explore the variation of \{CMFs\} with different roadway characteristics among treated sites over time. Therefore, in this study, we (1) evaluate the safety performance of a sample of urban four-lane roadway segments that have been widened with one through lane in each direction and (2) determine the relationship between the safety effects and different roadway characteristics over time. Observational before–after analysis with the empirical Bayes (EB) method was assessed in this study to evaluate the safety effects of widening urban four-lane roadways to six-lanes. Moreover, the nonlinearizing link functions were utilized to achieve better performance of crash modification functions (CMFunctions). The \{CMFunctions\} were developed using a Bayesian regression method including the estimated nonlinearizing link function to incorporate the changes in safety effects of the treatment over time. Data was collected for urban arterials in Florida, and the Florida-specific full \{SPFs\} were developed and used for \{EB\} estimation. The results indicated that the conversion of four-lane roadways to six-lane roadways resulted in a crash reduction of 15 percent for total crashes, and 24 percent for injury crashes on urban roadways. The results show that the safety effects vary across the sites with different roadway characteristics. In particular, \{LOS\} changes, time changes, and shoulder widths are significant parameters that affect the variation of CMFs. Moreover, it was found that narrowing shoulder and median widths to make space for an extra through lane shows a negative safety impact. It was also found that including the nonlinearizing link functions in developing \{CMFunctions\} shows more reliable estimates, if the variation of \{CMFs\} with specific parameters has a nonlinear relationship. The findings provide insights into the selection of roadway sites for adding through lanes. }
}
@article{Abuzwidah2015153,
title = {Safety assessment of the conversion of toll plazas to all-electronic toll collection system },
journal = {Accident Analysis & Prevention },
volume = {80},
number = {0},
pages = {153 - 161},
year = {2015},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2015.03.039},
url = {http://www.sciencedirect.com/science/article/pii/S0001457515001256},
author = {Muamer Abuzwidah and Mohamed Abdel-Aty},
keywords = {Toll plaza},
keywords = {All-electronic toll collection},
keywords = {Toll by plate},
keywords = {Crash modification factors},
keywords = {Accident modification factors},
keywords = {Highway safety manual },
abstract = {Abstract Traditional mainline toll plaza (TMTP) is considered the most high-risk location on the toll roads. Conversion from \{TMTP\} or hybrid mainline toll plaza (HMTP) to an all-electronic toll collection (AETC) system has demonstrated measured improvement in traffic operations and environmental issues. However, there is a lack of research that quantifies the safety impacts of these new tolling systems. This study evaluated the safety effectiveness of the conversion from \{TMTP\} or \{HMTP\} to \{AETC\} system. An extensive data collection was conducted that included hundred mainline toll plazas located on more than 750 miles of toll roads in Florida. Various observational before-after studies including the empirical Bayes method were applied. The results indicated that the conversion from the \{TMTP\} to an \{AETC\} system resulted in an average crash reduction of 76, 75, and 68% for total, fatal-and-injury and property damage only (PDO) crashes, respectively; for rear end and lane change related (LCR) crashes the average reductions were 80 and 74%, respectively. The conversion from \{HMTP\} to \{AETC\} system enhanced traffic safety by reducing crashes by 24, 28 and 20% of total, fatal-and-injury, and \{PDO\} crashes respectively; also, for rear end and \{LCR\} crashes, the average reductions were 15 and 22%, respectively. Overall, this paper provided an up-to-date safety impact of using different toll collection systems. The results proved that the \{AETC\} system significantly improved traffic safety for all crash categories; and changed toll plazas from the highest risk on Expressways to be similar to regular segments. }
}
@article{Lee2015146,
title = {Multivariate crash modeling for motor vehicle and non-motorized modes at the macroscopic level },
journal = {Accident Analysis & Prevention },
volume = {78},
number = {0},
pages = {146 - 154},
year = {2015},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2015.03.003},
url = {http://www.sciencedirect.com/science/article/pii/S0001457515000779},
author = {Jaeyoung Lee and Mohamed Abdel-Aty and Ximiao Jiang},
keywords = {Multivariate modeling},
keywords = {Macroscopic analysis},
keywords = {Bayesian modeling},
keywords = {Spatial modeling},
keywords = {Traffic analysis zones},
keywords = {Transportation safety planning },
abstract = {Abstract Macroscopic traffic crash analyses have been conducted to incorporate traffic safety into long-term transportation planning. This study aims at developing a multivariate Poisson lognormal conditional autoregressive model at the macroscopic level for crashes by different transportation modes such as motor vehicle, bicycle, and pedestrian crashes. Many previous studies have shown the presence of common unobserved factors across different crash types. Thus, it was expected that adopting multivariate model structure would show a better modeling performance since it can capture shared unobserved features across various types. The multivariate model and univariate model were estimated based on traffic analysis zones (TAZs) and compared. It was found that the multivariate model significantly outperforms the univariate model. It is expected that the findings from this study can contribute to more reliable traffic crash modeling, especially when focusing on different modes. Also, variables that are found significant for each mode can be used to guide traffic safety policy decision makers to allocate resources more efficiently for the zones with higher risk of a particular transportation mode. }
}
@article{AbdelAty2006335,
title = {Evaluation of variable speed limits for real-time freeway safety improvement },
journal = {Accident Analysis & Prevention },
volume = {38},
number = {2},
pages = {335 - 345},
year = {2006},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2005.10.010},
url = {http://www.sciencedirect.com/science/article/pii/S0001457505001764},
author = {Mohamed Abdel-Aty and Jeremy Dilmore and Albinder Dhindsa},
keywords = {Variable speed limit},
keywords = {Traffic safety},
keywords = {\{ITS\} applications},
keywords = {Crash potential},
keywords = {Micro-simulation },
abstract = {Use of various variable speed limit (VSL) strategies as a tool for safety improvement on freeways was evaluated using simulation of a section of Interstate 4 in Orlando, FL. Real-time crash likelihood was calculated based on models developed in previous research by the first author [Abdel-Aty, M., Uddin, N., Pande, A., January 2005. Split models for predicting multi-vehicle crashes during high-speed and low-speed operating conditions on freeways. In: Presented at the 84th Annual Meeting of the Transportation Research Board, Washington, DC]. \{VSL\} implementation produced safety improvement by simultaneously implementing lower speed limits upstream and higher speed limits downstream of the location where crash likelihood is observed in real-time. This improvement was realized in the case of medium-to-high-speed regimes on the freeway, but no benefit was achieved in low-speed situations (no substantial safety benefit from implementing \{VSL\} in congested situation's simulation). The final recommendations for implementing \{VSL\} are:• gradually introducing speed limit changes over time (5 mph every 10 min); • abruptly changing speed limit in space (no gap distance); • reducing speed limits upstream and increasing speed limits downstream of location of interest; • the speed limit changes up- and downstream should be large in magnitude (15 mph) and implemented within short distances (2 miles) of the location of interest. In addition to the safety benefit, this final strategy also produced travel time savings. }
}
@article{Shi2015,
title = {Big Data applications in real-time traffic operation and safety monitoring and improvement on urban expressways },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {},
number = {0},
pages = { - },
year = {2015},
note = {},
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/j.trc.2015.02.022},
url = {http://www.sciencedirect.com/science/article/pii/S0968090X15000777},
author = {Qi Shi and Mohamed Abdel-Aty},
keywords = {Big Data},
keywords = {Real-time},
keywords = {Congestion},
keywords = {Safety},
keywords = {Urban expressway },
abstract = {Abstract The advent of Big Data era has transformed the outlook of numerous fields in science and engineering. The transportation arena also has great expectations of taking the advantage of Big Data enabled by the popularization of Intelligent Transportation Systems (ITS). In this study, the viability of a proactive real-time traffic monitoring strategy evaluating operation and safety simultaneously was explored. The objective is to improve the system performance of urban expressways by reducing congestion and crash risk. In particular, Microwave Vehicle Detection System (MVDS) deployed on an expressway network in Orlando was utilized to achieve the objectives. The system consisting of 275 detectors covers 75 miles of the expressway network, with average spacing less than 1 mile. Comprehensive traffic flow parameters per lane are continuously archived on one-minute interval basis. The scale of the network, dense deployment of detection system, richness of information and continuous collection turn \{MVDS\} as the ideal source of Big Data. It was found that congestion on urban expressways was highly localized and time-specific. As expected, the morning and evening peak hours were the most congested time periods. The results of congestion evaluation encouraged real-time safety analysis to unveil the effects of traffic dynamics on crash occurrence. Data mining (random forest) and Bayesian inference techniques were implemented in real-time crash prediction models. The identified effects, both indirect (peak hour, higher volume and lower speed upstream of crash locations) and direct (higher congestion index downstream to crash locations) congestion indicators confirmed the significant impact of congestion on rear-end crash likelihood. As a response, reliability analysis was introduced to determine the appropriate time to trigger safety warnings according to the congestion intensity. Findings of this paper demonstrate the importance to jointly monitor and improve traffic operation and safety. The Big Data generated by the \{ITS\} systems is worth further exploration to bring all their full potential for more proactive traffic management. }
}
@article{Park2015310,
title = {Development of adjustment functions to assess combined safety effects of multiple treatments on rural two-lane roadways },
journal = {Accident Analysis & Prevention },
volume = {75},
number = {0},
pages = {310 - 319},
year = {2015},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2014.12.012},
url = {http://www.sciencedirect.com/science/article/pii/S0001457514003911},
author = {Juneyoung Park and Mohamed Abdel-Aty},
keywords = {Safety effectiveness},
keywords = {Crash modification factors and functions},
keywords = {Multiple treatments},
keywords = {Combining method},
keywords = {Adjustment factors and functions},
keywords = {Empirical Bayes},
keywords = {Highway Safety Manual },
abstract = {Abstract Numerous studies have attempted to evaluate the safety effectiveness of specific single treatment on roadways by estimating crash modification factors (CMFs). However, there is a need to also assess safety effects of multiple treatments since multiple treatments are usually simultaneously applied to roadways. Due to the lack of sufficient \{CMFs\} of multiple treatments, the Highway Safety Manual (HSM) provides combining method for multiple CMFs. However, it is cautioned in the \{HSM\} and related sources that combined safety effect of multiple \{CMFs\} may be over or under estimated. Moreover, the literature did not evaluate the accuracy of the combining method using \{CMFs\} obtained from the same study area. Thus, the main objectives of this research are: (1) to estimate \{CMFs\} and crash modification functions (CM Functions) for two single treatments (shoulder rumble strips, widening (1–9 ft) shoulder width) and combination (installing shoulder rumble strips + widening shoulder width) using the observational before–after with empirical Bayes (EB) method and (2) to develop adjustment factors and functions to assess combined safety effects of multiple treatments based on the accuracy of the combined \{CMFs\} for multiple treatments estimated by the existing combining method. Data was collected for rural two-lane roadways in Florida and Florida-specific safety performance functions (SPFs) were estimated for different crash types and severities. The \{CM\} Functions and adjustment functions were developed using linear and nonlinear regression models. The results of before–after with \{EB\} method show that the two single treatments and combination are effective in reducing total and \{SVROR\} (single vehicle run-off roadway) crashes. The results indicate that the treatments were more safety effective for the roadway segments with narrower original shoulder width in the before period. It was found that although the \{CMFs\} for multiple treatments (i.e., combination of two single treatments) were generally lower than \{CMFs\} for single treatments, they were getting similar to the roadway segments with wider shoulder width. The findings indicate that the combined safety effects of multiple treatments using \{HSM\} combining method are mostly over-estimated and the accuracy of \{HSM\} combining method vary based on crash types and severity levels. Therefore, it is recommended to develop and apply the adjustment factors and functions to predict the safety effects of multiple treatments when the \{HSM\} combining method is used. }
}
@article{Lee201564,
title = {Multi-level hot zone identification for pedestrian safety },
journal = {Accident Analysis & Prevention },
volume = {76},
number = {0},
pages = {64 - 73},
year = {2015},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2015.01.006},
url = {http://www.sciencedirect.com/science/article/pii/S0001457515000172},
author = {Jaeyoung Lee and Mohamed Abdel-Aty and Keechoo Choi and Helai Huang},
keywords = {Pedestrian safety},
keywords = {Bayesian approach},
keywords = {Spatial error modeling},
keywords = {Gaussian conditional autoregressive},
keywords = {\{CAR\}},
keywords = {Screening},
keywords = {Macroscopic analysis},
keywords = {Poisson lognormal model},
keywords = {Simultaneous equations modeling },
abstract = {Abstract According to the National Highway Traffic Safety Administration (NHTSA), while fatalities from traffic crashes have decreased, the proportion of pedestrian fatalities has steadily increased from 11% to 14% over the past decade. This study aims at identifying two zonal levels factors. The first is to identify hot zones at which pedestrian crashes occurs, while the second are zones where crash-involved pedestrians came from. Bayesian Poisson lognormal simultaneous equation spatial error model (BPLSESEM) was estimated and revealed significant factors for the two target variables. Then, \{PSIs\} (potential for safety improvements) were computed using the model. Subsequently, a novel hot zone identification method was suggested to combine both hot zones from where vulnerable pedestrians originated with hot zones where many pedestrian crashes occur. For the former zones, targeted safety education and awareness campaigns can be provided as countermeasures whereas area-wide engineering treatments and enforcement may be effective safety treatments for the latter ones. Thus, it is expected that practitioners are able to suggest appropriate safety treatments for pedestrian crashes using the method and results from this study. }
}
@article{Yu201568,
title = {A correlated random parameter approach to investigate the effects of weather conditions on crash risk for a mountainous freeway },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {50},
number = {0},
pages = {68 - 77},
year = {2015},
note = {Special Issue on Road Safety and Simulation },
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/j.trc.2014.09.016},
url = {http://www.sciencedirect.com/science/article/pii/S0968090X14002861},
author = {Rongjie Yu and Yingge Xiong and Mohamed Abdel-Aty},
keywords = {Aggregate traffic safety},
keywords = {Correlated random parameter model},
keywords = {Tobit model},
keywords = {Weather warning system },
abstract = {Abstract Freeway crashes are highly influenced by weather conditions, especially for a mountainous freeway affected by adverse weather conditions. In order to reduce crash occurrence, a variety of weather monitoring systems and Intelligent Transportation Systems (ITS) have been introduced to address the weather impact. However, the effects of weather conditions on crash occurrence have not been fully investigated and understood. With detailed weather information from weather monitoring stations, this study seeks to investigate the complex effects of weather factors, such as visibility and precipitation, on crash occurrence based on safety performance functions. Unlike conventional traffic safety studies which deal with crash frequency, crash rates per 100 million vehicle miles travelled were adopted as the dependent variable in this study. Three years of weather related crash data from a 15 mile mountainous freeway on I-70 in Colorado were utilized. First, a fixed parameter Tobit model was estimated to unveil the effects of explanatory variables on crash rates. Then, in order to characterize the heterogeneous effects of weather conditions across the homogeneous segments, a traditional random parameter Tobit model was developed. Furthermore, for the purpose of monitoring the intricate interactions between weather conditions and geometric characteristics, a multivariate structure for the distribution of random parameters was introduced; which result in a correlated random parameter Tobit model. Likelihood ratio test results demonstrated that the correlated random parameter Tobit model was superior to the uncorrelated random parameter and fixed parameter Tobit models. Moreover, visibility and precipitation variables were found to have substantial correlations with geometric characteristics like steep downgrade slopes and curve segments. Results from the models will shed lights on future applications of weather warning systems to improve traffic safety. }
}
@article{Ahmed2015130,
title = {Evaluation and spatial analysis of automated red-light running enforcement cameras },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {50},
number = {0},
pages = {130 - 140},
year = {2015},
note = {Special Issue on Road Safety and Simulation },
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/j.trc.2014.07.012},
url = {http://www.sciencedirect.com/science/article/pii/S0968090X14002149},
author = {Mohamed M. Ahmed and Mohamed Abdel-Aty},
keywords = {Evaluation of red light cameras},
keywords = {Driver behavior},
keywords = {Safety effectiveness},
keywords = {Highway safety manual},
keywords = {Empirical Bayes },
abstract = {Abstract Red light cameras may have a demonstrable impact on reducing the frequency of red light running violations; however, their effect on the overall safety at intersections is still up for debate. This paper examined the safety impacts of Red Light Cameras (RLCs) on traffic crashes at signalized intersections using the Empirical Bayes (EB) method. Data were obtained from the Florida Department of Transportation for twenty-five \{RLC\} equipped intersections in Orange County, Florida. Additional fifty intersections that remained with no photo enforcement in the vicinity of the treated sites were collected to examine the spillover effects on the same corridors. The safety evaluation was performed at three main levels; only target approaches where \{RLCs\} were installed, all approaches on \{RLC\} intersections, and non-RLC intersections located on the same travel corridors as the camera equipped intersections. Moreover, the spatial spillover effects of \{RLCs\} were also examined on an aggregate level to evaluate the safety impacts on driver behavior at a regional scale. The results from this study indicated that there was a consistent significant reduction in angle and left-turn crashes and a significant increase in rear-end crashes on target approaches, in addition, the magnitude and the direction of these effects, to a lesser degree, were found similar on the whole intersection. Similar trends in shift of crash types were spilled-over to non-RLC intersections in the proximity of the treated sites. On an aggregate county level, there was a moderate spillover benefits with a notable crash migration to the boundary of the county. }
}
@article{Ahmed2014309,
title = {Real-time assessment of fog-related crashes using airport weather data: A feasibility analysis },
journal = {Accident Analysis & Prevention },
volume = {72},
number = {0},
pages = {309 - 317},
year = {2014},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2014.07.004},
url = {http://www.sciencedirect.com/science/article/pii/S0001457514002000},
author = {Mohamed M. Ahmed and Mohamed Abdel-Aty and Jaeyoung Lee and Rongjie Yu},
keywords = {Real-time weather data},
keywords = {Airport weather information},
keywords = {Crash risk},
keywords = {Bayesian logistic regression},
keywords = {Fog},
keywords = {Visibility obstruction },
abstract = {Abstract The effect of reduction of visibility on crash occurrence has recently been a major concern. Although visibility detection systems can help to mitigate the increased hazard of limited-visibility, such systems are not widely implemented and many locations with no systems are experiencing considerable number of fatal crashes due to reduction in visibility caused by fog and inclement weather. On the other hand, airports’ weather stations continuously monitor all climate parameters in real-time, and the gathered data may be utilized to mitigate the increased risk for the adjacent roadways. This study aims to examine the viability of using airport weather information in real-time road crash risk assessment in locations with recurrent fog problems. Bayesian logistic regression was utilized to link six years (2005–2010) of historical crash data to real-time weather information collected from eight airports in the State of Florida, roadway characteristics and aggregate traffic parameters. The results from this research indicate that real-time weather data collected from adjacent airports are good predictors to assess increased risk on highways. }
}
@article{Lee201583,
title = {Development of crash modification factors for changing lane width on roadway segments using generalized nonlinear models },
journal = {Accident Analysis & Prevention },
volume = {76},
number = {0},
pages = {83 - 91},
year = {2015},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2015.01.007},
url = {http://www.sciencedirect.com/science/article/pii/S0001457515000184},
author = {Chris Lee and Mohamed Abdel-Aty and Juneyoung Park and Jung-Han Wang},
keywords = {Crash modification factor},
keywords = {Generalized nonlinear model},
keywords = {Lane width},
keywords = {Speed limit},
keywords = {Roadway segment },
abstract = {Abstract This study evaluates the effectiveness of changing lane width in reducing crashes on roadway segments. To consider nonlinear relationships between crash rate and lane width, the study develops generalized nonlinear models (GNMs) using 3-years crash records and road geometry data collected for all roadway segments in Florida. The study also estimates various crash modification factors (CMFs) for different ranges of lane width based on the results of the GNMs. It was found that the crash rate was highest for 12-ft lane and lower for the lane width less than or greater than 12 ft. \{GNMs\} can extrapolate this nonlinear continuous effect of lane width and estimate the \{CMFs\} for any lane width, not only selected lane widths, unlike generalized linear models (GLMs) with categorical variables. The \{CMFs\} estimated using \{GNMs\} reflect that crashes are less likely to occur for narrower lanes if the lane width is less than 12 ft whereas crashes are less likely to occur for wider lanes if the lane width is greater than 12 ft. However, these effects varied with the posted speed limits as the effect of interaction between lane width and speed limit was significant. The estimated \{CMFs\} show that crashes are less likely to occur for lane widths less than 12 ft than the lane widths greater than 12 ft if the speed limit is higher than or equal to 40 mph. It was also found from the \{CMFs\} that crashes at higher severity levels (KABC and KAB) are less likely to occur for lane widths greater or less than 12 ft compared to 12-ft lane. The study demonstrates that the \{CMFs\} estimated using \{GNMs\} clearly reflect variations in crashes with lane width, which cannot be captured by the \{CMFs\} estimated using GLMs. Thus, it is recommended that if the relationship between crash rate and lane width is nonlinear, the \{CMFs\} are estimated using GNMs. }
}
@article{Lee20146,
title = {Analysis of residence characteristics of at-fault drivers in traffic crashes },
journal = {Safety Science },
volume = {68},
number = {0},
pages = {6 - 13},
year = {2014},
note = {},
issn = {0925-7535},
doi = {http://dx.doi.org/10.1016/j.ssci.2014.02.019},
url = {http://www.sciencedirect.com/science/article/pii/S0925753514000459},
author = {Jaeyoung Lee and Mohamed Abdel-Aty and Keechoo Choi},
keywords = {Bayesian modeling},
keywords = {Poisson-lognormal model},
keywords = {Residence analysis},
keywords = {\{ZIP\} code},
keywords = {Socioeconomic factors},
keywords = {Census data },
abstract = {Abstract In recent years many studies have investigated traffic crashes with various contributing factors at the macroscopic level. Nevertheless, while previous studies have concentrated only on zones where the crash occurred, there have been few studies that focused on residence characteristics associated with the origin of the drivers causing traffic crashes, so called at-fault drivers. Intuitively, it is reasonable to assume that the number of at-fault drivers is related to socio-demographic features of the at-fault drivers’ residence area. Thus, the main objective of this study is to find out the relationship between the number of at-fault drivers and zonal characteristics of the residence where at-fault drivers came from. The Bayesian Poisson-lognormal model was adopted to find out the contributing factors of the residence zones on the number of crashes based on the at-fault drivers. The findings from the study implied that the crash occurrence is not only affected by roadway/traffic factors but also by several demographic and socioeconomic characteristics of residence zones. The result from this study can be used to identify zones with a higher potential of at-fault drivers; thus we can concentrate on these zones for safety treatments, including more targeted awareness, education or stricter enforcement. }
}
@article{Yu2014235,
title = {An optimal variable speed limits system to ameliorate traffic safety risk },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {46},
number = {0},
pages = {235 - 246},
year = {2014},
note = {},
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/j.trc.2014.05.016},
url = {http://www.sciencedirect.com/science/article/pii/S0968090X1400165X},
author = {Rongjie Yu and Mohamed Abdel-Aty},
keywords = {Variable speed limit},
keywords = {Traffic safety},
keywords = {Driver compliance},
keywords = {Crash risk},
keywords = {Micro-simulation },
abstract = {Abstract Active Traffic Management (ATM) systems have been emerging in recent years in the \{US\} and Europe. They provide control strategies to improve traffic flow and reduce congestion on freeways. This study investigates the feasibility of utilizing a Variable Speed Limits (VSL) system, one key part of ATM, to improve traffic safety on freeways. A proactive traffic safety improvement \{VSL\} control algorithm is proposed. First, an extension of the \{METANET\} (METANET: A macroscopic simulation program for motorway networks) traffic flow model is employed to analyze VSL’s impact on traffic flow. Then, a real-time crash risk evaluation model is estimated for the purpose of quantifying crash risk. Finally, optimal \{VSL\} control strategies are achieved by employing an optimization technique to minimize the total crash risk along the \{VSL\} implementation corridor. Constraints are setup to limit the increase of average travel time and the differences of the posted speed limits temporarily and spatially. This novel \{VSL\} control algorithm can proactively reduce crash risk and therefore improve traffic safety. The proposed \{VSL\} control algorithm is implemented and tested for a mountainous freeway bottleneck area through the micro-simulation software VISSIM. Safety impacts of the \{VSL\} system are quantified as crash risk improvements and speed homogeneity improvements. Moreover, three different driver compliance levels are modeled in \{VISSIM\} to monitor the sensitivity of \{VSL\} effects on driver compliance. Conclusions demonstrated that the proposed \{VSL\} system could improve traffic safety by decreasing crash risk and enhancing speed homogeneity under both the high and moderate compliance levels; while the \{VSL\} system fails to significantly enhance traffic safety under the low compliance scenario. Finally, future implementation suggestions of the \{VSL\} control strategies and related research topics are also discussed. }
}
@article{Yang201533,
title = {A hazard-based duration model for analyzing crossing behavior of cyclists and electric bike riders at signalized intersections },
journal = {Accident Analysis & Prevention },
volume = {74},
number = {0},
pages = {33 - 41},
year = {2015},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2014.10.014},
url = {http://www.sciencedirect.com/science/article/pii/S000145751400311X},
author = {Xiaobao Yang and Mei Huan and Mohamed Abdel-Aty and Yichuan Peng and Ziyou Gao},
keywords = {Cyclist},
keywords = {Electric bike},
keywords = {Red-light running},
keywords = {Waiting time},
keywords = {Hazard-based duration model},
keywords = {Intersection },
abstract = {Abstract This paper presents a hazard-based duration approach to investigate riders’ waiting times, violation hazards, associated risk factors, and their differences between cyclists and electric bike riders at signalized intersections. A total of 2322 two-wheeled riders approaching the intersections during red light periods were observed in Beijing, China. The data were classified into censored and uncensored data to distinguish between safe crossing and red-light running behavior. The results indicated that the red-light crossing behavior of most riders was dependent on waiting time. They were inclined to terminate waiting behavior and run against the traffic light with the increase of waiting duration. Over half of the observed riders cannot endure 49 s or longer. 25% of the riders can endure 97 s or longer. Rider type, gender, waiting position, conformity tendency and crossing traffic volume were identified to have significant effects on riders’ waiting times and violation hazards. Electric bike riders were found to be more sensitive to the external risk factors such as other riders’ crossing behavior and crossing traffic volume than cyclists. Moreover, unobserved heterogeneity was examined in the proposed models. The finding of this paper can explain when and why cyclists and electric bike riders run against the red light at intersections. The results of this paper are useful for traffic design and management agencies to implement strategies to enhance the safety of riders. }
}
@article{Lee201413,
title = {Development of zone system for macro-level traffic safety analysis },
journal = {Journal of Transport Geography },
volume = {38},
number = {0},
pages = {13 - 21},
year = {2014},
note = {},
issn = {0966-6923},
doi = {http://dx.doi.org/10.1016/j.jtrangeo.2014.04.018},
url = {http://www.sciencedirect.com/science/article/pii/S0966692314000854},
author = {Jaeyoung Lee and Mohamed Abdel-Aty and Ximiao Jiang},
keywords = {Traffic safety analysis zones},
keywords = {Macro-level analysis},
keywords = {\{MAUP\}},
keywords = {Bayesian Poisson Log-normal model},
keywords = {Transportation safety planning},
keywords = {Regionalization },
abstract = {Abstract Various geographic units have been used in macro-level modeling. Amongst these units, traffic analysis zones (TAZs) have been broadly employed in many macroscopic safety studies. Nevertheless, no studies questioned the validity of \{TAZs\} for crash analysis at the macro-level crash modeling. In this study, we point out several possible problems of \{TAZs\} as spatial units for macroscopic safety studies. Current \{TAZs\} with homogenous crash rates were combined into new single zones. Then we created ten new zonal systems by different zone aggregation levels. The optimal zonal scale for traffic safety analysis zones (TSAZ) was determined using the Brown-Forsythe test. It was found that the zone system with about 1:2 aggregation was the optimal zone system for macroscopic safety modeling. Thus we develop what we call traffic safety analysis zones (TSAZs) that has the potential of reducing several possible problems of TAZs. Also it was shown that \{TSAZ\} based models had better fit compared to \{TAZ\} based models. }
}
@article{Xu2014110,
title = {Sensitivity analysis in the context of regional safety modeling: Identifying and assessing the modifiable areal unit problem },
journal = {Accident Analysis & Prevention },
volume = {70},
number = {0},
pages = {110 - 120},
year = {2014},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2014.02.012},
url = {http://www.sciencedirect.com/science/article/pii/S0001457514000517},
author = {Pengpeng Xu and Helai Huang and Ni Dong and Mohamed Abdel-Aty},
keywords = {Modifiable areal unit problem},
keywords = {Sensitivity analysis},
keywords = {Regional safety prediction model},
keywords = {\{REDCAP\} },
abstract = {Abstract A wide array of spatial units has been explored in current regional safety analysis. Since traffic crashes exhibit extreme spatiotemporal heterogeneity which has rarely been a consideration in partitioning these zoning systems, research based on these areal units may be subjected to the modifiable areal unit problem (MAUP). This study attempted to conduct a sensitivity analysis to quantitatively investigate the \{MAUP\} effect in the context of regional safety modeling. The emerging regionalization method-RECDAP (regionalization with dynamically constrained agglomerative clustering and partitioning) was employed to aggregate 738 traffic analysis zones in the county of Hillsborough to 14 zoning schemes at an incremental step-size of 50 zones based on spatial homogeneity of crash risk. At each level of aggregation, a Bayesian Poisson lognormal model and a Bayesian spatial model were calibrated to explain observed variations in total/severe crash counts given a number of zone-level factors. Results revealed that as the number of zones increases, the spatial autocorrelation of crash data increases. The Bayesian spatial model outperforms the Bayesian Poisson-lognormal model in accurately accounting for spatial autocorrelation effects, unbiased parameter estimates, and model performance, especially in cases with higher disaggregated levels. Zoning schemes with higher number of zones tend to have increasing number of significant variables, more stable coefficient estimation, smaller standard error, whereas worse model performance. The variables of population density and median household income show consistently significant effects on crash risk and are robust to variation in data aggregation. The \{MAUP\} effects may be significantly reduced if we just maintain at about 50% of the original number of zones (350 or larger). The present study highlights \{MAUP\} that is generally ignored by transportation safety analysts, and provides insights into the nature of parameter sensitivity to data aggregation in the context of regional safety modeling. }
}
@article{Park2015179,
title = {Developing crash modification functions to assess safety effects of adding bike lanes for urban arterials with different roadway and socio-economic characteristics },
journal = {Accident Analysis & Prevention },
volume = {74},
number = {0},
pages = {179 - 191},
year = {2015},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2014.10.024},
url = {http://www.sciencedirect.com/science/article/pii/S0001457514003212},
author = {Juneyoung Park and Mohamed Abdel-Aty and Jaeyoung Lee and Chris Lee},
keywords = {Safety effectiveness},
keywords = {Crash modification factors},
keywords = {Simple and full crash modification functions},
keywords = {Heterogeneous effect},
keywords = {Before–after method},
keywords = {Adding a bike lane },
abstract = {Abstract Although many researchers have estimated crash modification factors (CMFs) for specific treatments (or countermeasures), there is a lack of studies that explored the heterogeneous effects of roadway characteristics on crash frequency among treated sites. Generally, the \{CMF\} estimated by before–after studies represents overall safety effects of the treatment in a fixed value. However, as each treated site has different roadway characteristics, there is a need to assess the variation of \{CMFs\} among the treated sites with different roadway characteristics through crash modification functions (CMFunctions). The main objective of this research is to determine relationships between the safety effects of adding a bike lane and the roadway characteristics through (1) evaluation of \{CMFs\} for adding a bike lane using observational before–after with empirical Bayes (EB) and cross-sectional methods, and (2) development of simple and full \{CMFunctions\} which are describe the \{CMF\} in a function of roadway characteristics of the sites. Data was collected for urban arterials in Florida, and the Florida-specific full \{SPFs\} were developed. Moreover, socio-economic parameters were collected and included in \{CMFunctions\} and \{SPFs\} (1) to capture the effects of the variables that represent volume of bicyclists and (2) to identify general relationship between the \{CMFs\} and these characteristics. In order to achieve better performance of CMFunctions, data mining techniques were used. The results of both before–after and cross-sectional methods show that adding a bike lane on urban arterials has positive safety effects (i.e., CMF < 1) for all crashes and bike crashes. It was found that adding a bike lane is more effective in reducing bike crashes than all crashes. It was also found that the \{CMFs\} vary across the sites with different roadway characteristics. In particular, annual average daily traffic (AADT), number of lanes, \{AADT\} per lane, median width, bike lane width, and lane width are significant characteristics that affect the variation in safety effects of adding a bike lane. Some socio-economic characteristics such as bike commuter rate and population density also have significant effect on the variation in CMFs. The findings suggest that full \{CMFunctions\} showed better model fit than simple \{CMFuncttions\} since they account for the heterogeneous effects of multiple roadway and socio-economic characteristics. The proposed \{CMFunctions\} provide insights into bike lane design and selection of sites for bike lane installation for reducing crashes. }
}
@article{Wang201537,
title = {Estimating safety performance trends over time for treatments at intersections in Florida },
journal = {Accident Analysis & Prevention },
volume = {80},
number = {0},
pages = {37 - 47},
year = {2015},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2015.03.015},
url = {http://www.sciencedirect.com/science/article/pii/S0001457515000895},
author = {Jung-Han Wang and Mohamed A. Abdel-Aty and Juneyoung Park and Chris Lee and Pei-Fen Kuo},
keywords = {Crash Modification Factor},
keywords = {Crash Modification Function},
keywords = {Intersection},
keywords = {Signalization},
keywords = {Red light running camera},
keywords = {Time series model},
keywords = {\{ARMA\} },
abstract = {Abstract Researchers have put great efforts in quantifying Crash Modification Factors (CMFs) for diversified treatment types. In the Highway Safety Manual (HSM), \{CMFs\} have been identified to predict safety effectiveness of converting a stop-controlled to a signal-controlled intersection (signalization) and installing Red Light Running Cameras (RLCs). Previous studies showed that both signalization and adding \{RLCs\} reduced angle crashes but increased rear-end crashes. However, some studies showed that \{CMFs\} varied over time after the treatment was implemented. Thus, the objective of this study is to investigate trends of \{CMFs\} for the signalization and adding \{RLCs\} over time. \{CMFs\} for the two treatments were measured in each month and 90-day moving windows respectively. The \{ARMA\} time series model was applied to predict trends of \{CMFs\} over time based on monthly variations in CMFs. The results of the signalization show that the \{CMFs\} for rear-end crashes were lower at the early phase after the signalization but gradually increased from the 9th month. On the other hand, the \{CMFs\} for angle crashes were higher at the early phase after adding \{RLCs\} but decreased after the 9th month and then became stable. It was also found that the \{CMFs\} for total and fatal/injury crashes after adding \{RLCs\} in the first 18 months were significantly greater than the \{CMFs\} in the following 18 months. This indicates that there was a lag effect of the treatments on safety performance. The results of the \{ARMA\} model show that the model can better predict trends of the \{CMFs\} for the signalization and adding \{RLCs\} when the \{CMFs\} are calculated in 90-day moving windows compared to the \{CMFs\} calculated in each month. In particular, the \{ARMA\} model predicted a significant safety effect of the signalization on reducing angle and left-turn crashes in the long term. Thus, it is recommended that the safety effects of the treatment be assessed using the \{ARMA\} model based on trends of \{CMFs\} in the long term after the implementation of the treatment. }
}
@article{Yu201397,
title = {Multi-level Bayesian analyses for single- and multi-vehicle freeway crashes },
journal = {Accident Analysis & Prevention },
volume = {58},
number = {0},
pages = {97 - 105},
year = {2013},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2013.04.025},
url = {http://www.sciencedirect.com/science/article/pii/S0001457513001681},
author = {Rongjie Yu and Mohamed Abdel-Aty},
keywords = {Safety performance functions},
keywords = {Bivariate Poisson-lognormal model},
keywords = {Random parameter},
keywords = {Bayesian logistic regression},
keywords = {Mountainous freeway },
abstract = {Abstract This study presents multi-level analyses for single- and multi-vehicle crashes on a mountainous freeway. Data from a 15-mile mountainous freeway section on I-70 were investigated. Both aggregate and disaggregate models for the two crash conditions were developed. Five years of crash data were used in the aggregate investigation, while the disaggregate models utilized one year of crash data along with real-time traffic and weather data. For the aggregate analyses, safety performance functions were developed for the purpose of revealing the contributing factors for each crash type. Two methodologies, a Bayesian bivariate Poisson-lognormal model and a Bayesian hierarchical Poisson model with correlated random effects, were estimated to simultaneously analyze the two crash conditions with consideration of possible correlations. Except for the factors related to geometric characteristics, two exposure parameters (annual average daily traffic and segment length) were included. Two different sets of significant explanatory and exposure variables were identified for the single-vehicle (SV) and multi-vehicle (MV) crashes. It was found that the Bayesian bivariate Poisson-lognormal model is superior to the Bayesian hierarchical Poisson model, the former with a substantially lower \{DIC\} and more significant variables. In addition to the aggregate analyses, microscopic real-time crash risk evaluation models were developed for the two crash conditions. Multi-level Bayesian logistic regression models were estimated with the random parameters accounting for seasonal variations, crash-unit-level diversity and segment-level random effects capturing unobserved heterogeneity caused by the geometric characteristics. The model results indicate that the effects of the selected variables on crash occurrence vary across seasons and crash units; and that geometric characteristic variables contribute to the segment variations: the more unobserved heterogeneity have been accounted, the better classification ability. Potential applications of the modeling results from both analysis approaches are discussed. }
}
@article{Yu201391,
title = {Investigating the different characteristics of weekday and weekend crashes },
journal = {Journal of Safety Research },
volume = {46},
number = {0},
pages = {91 - 97},
year = {2013},
note = {},
issn = {0022-4375},
doi = {http://dx.doi.org/10.1016/j.jsr.2013.05.002},
url = {http://www.sciencedirect.com/science/article/pii/S0022437513000467},
author = {Rongjie Yu and Mohamed Abdel-Aty},
keywords = {Multivariate Poisson model},
keywords = {Weekend crash},
keywords = {Random effects Bayesian logistic regression},
keywords = {Mountainous freeway traffic safety },
abstract = {AbstractIntroduction This study provides a systematic approach to investigate the different characteristics of weekday and weekend crashes. Method Weekend crashes were defined as crashes occurring between Friday 9 p.m. and Sunday 9 p.m., while the other crashes were labeled as weekday crashes. In order to reveal the various features for weekday and weekend crashes, multi-level traffic safety analyses have been conducted. For the aggregate analysis, crash frequency models have been developed through Bayesian inference technique; correlation effects of weekday and weekend crash frequencies have been accounted. A multivariate Poisson model and correlated random effects Poisson model were estimated; model goodness-of-fits have been compared through \{DIC\} values. In addition to the safety performance functions, a disaggregate crash time propensity model was calibrated with Bayesian logistic regression model. Moreover, in order to account for the cross-section unobserved heterogeneity, random effects Bayesian logistic regression model was employed. Results It was concluded that weekday crashes are more probable to happen during congested sections, while the weekend crashes mostly occur under free flow conditions. Finally, for the purpose of confirming the aforementioned conclusions, real-time crash prediction models have been developed. Random effects Bayesian logistic regression models incorporating the microscopic traffic data were developed. Results of the real-time crash prediction models are consistent with the crash time propensity analysis. Furthermore, results from these models would shed some lights on future geometric improvements and traffic management strategies to improve traffic safety. Impact on Industry Utilizing safety performance to identify potential geometric improvements to reduce crash occurrence and monitoring real-time crash risks to pro-actively improve traffic safety. }
}
@article{Yu2014161,
title = {Using hierarchical Bayesian binary probit models to analyze crash injury severity on high speed facilities with real-time traffic data },
journal = {Accident Analysis & Prevention },
volume = {62},
number = {0},
pages = {161 - 167},
year = {2014},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2013.08.009},
url = {http://www.sciencedirect.com/science/article/pii/S0001457513003205},
author = {Rongjie Yu and Mohamed Abdel-Aty},
keywords = {Crash injury severity},
keywords = {Binary probit model},
keywords = {Random effects},
keywords = {Hierarchical probit model},
keywords = {Bayesian inference },
abstract = {Abstract Severe crashes are causing serious social and economic loss, and because of this, reducing crash injury severity has become one of the key objectives of the high speed facilities’ (freeway and expressway) management. Traditional crash injury severity analysis utilized data mainly from crash reports concerning the crash occurrence information, drivers’ characteristics and roadway geometric related variables. In this study, real-time traffic and weather data were introduced to analyze the crash injury severity. The space mean speeds captured by the Automatic Vehicle Identification (AVI) system on the two roadways were used as explanatory variables in this study; and data from a mountainous freeway (I-70 in Colorado) and an urban expressway (State Road 408 in Orlando) have been used to identify the analysis result's consistence. Binary probit (BP) models were estimated to classify the non-severe (property damage only) crashes and severe (injury and fatality) crashes. Firstly, Bayesian \{BP\} models’ results were compared to the results from Maximum Likelihood Estimation \{BP\} models and it was concluded that Bayesian inference was superior with more significant variables. Then different levels of hierarchical Bayesian \{BP\} models were developed with random effects accounting for the unobserved heterogeneity at segment level and crash individual level, respectively. Modeling results from both studied locations demonstrate that large variations of speed prior to the crash occurrence would increase the likelihood of severe crash occurrence. Moreover, with considering unobserved heterogeneity in the Bayesian \{BP\} models, the model goodness-of-fit has improved substantially. Finally, possible future applications of the model results and the hierarchical Bayesian probit models were discussed. }
}
@article{Yu201450,
title = {Analyzing crash injury severity for a mountainous freeway incorporating real-time traffic and weather data },
journal = {Safety Science },
volume = {63},
number = {0},
pages = {50 - 56},
year = {2014},
note = {},
issn = {0925-7535},
doi = {http://dx.doi.org/10.1016/j.ssci.2013.10.012},
url = {http://www.sciencedirect.com/science/article/pii/S0925753513002373},
author = {Rongjie Yu and Mohamed Abdel-Aty},
keywords = {Crash injury severity},
keywords = {Random parameter logit model},
keywords = {Support vector machine},
keywords = {Traffic safety},
keywords = {Microscopic traffic data },
abstract = {Abstract This study focuses on developing crash injury severity analysis models for a mountainous freeway section. In addition to the data obtained from crash reports, real-time traffic and weather data were utilized. The introduction of real-time data would benefit model applications on crash injury severity prediction. Crash injury severity was classified as a binary outcome (severe and non-severe crashes) and random forest model was firstly estimated to select the most important explanatory variables associated with severe crash occurrence. Four most critical variables (snow season indicator, steep grade indicator, speed standard deviation, and temperature) were chosen by the random forest model as inputs for the modeling analyses. For the purpose of identifying actual relationships between severe crash occurrence and the chosen explanatory variables and enhancing model goodness-of-fit, a total of three models were developed to analyze crash injury severity: (1) fixed parameter logit model; (2) support vector machine (SVM) model with radial-basis kernel function to detect non-linearity; and (3) random parameter logit model with unrestricted variance–covariance matrix to account for individual heterogeneity and also to investigate potential correlations between the explanatory variables. The three models were compared based on the areas under the \{ROC\} curve (AUC) values and it was demonstrated that \{SVM\} model and random parameter model provide superior model fits than the fixed parameter logit model. Findings of this study demonstrate that real-time traffic and weather variables have substantial influences on crash injury severity, which could be utilized to predict crash injury severity. Moreover, it is important to consider possible non-linearity and individual heterogeneity when analyzing crash injury severity. In addition, potential applications of the modeling results, limitations of this study have been discussed. }
}
@article{Wu201372,
title = {A novel visible network approach for freeway crash analysis },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {36},
number = {0},
pages = {72 - 82},
year = {2013},
note = {},
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/j.trc.2013.08.005},
url = {http://www.sciencedirect.com/science/article/pii/S0968090X13001691},
author = {Jianjun Wu and Mohamed Abdel-Aty and Rongjie Yu and Ziyou Gao},
keywords = {Freeway safety},
keywords = {Crash data},
keywords = {Safety analysis},
keywords = {Visible network },
abstract = {Abstract Freeway crashes have attracted considerable attention in recent years leading to the development of various methodologies to unveil the crash occurrence mechanisms including two general modeling approaches: parametric and non-parametric. In this paper, a novel visible network approach has been proposed to analyze crash characteristics with real-time traffic and weather data. In the suggested model, traffic states prior to crash occurrence have been extracted from real-time data; and crashes are mapped as nodes on the network. Each node contains information for the most hazardous factors relate to crash occurrence selected by random forest algorithm. With the help of transferring technology, links are connected between the nodes according to the state values. Therefore, complete freeway crash evolution networks can be obtained by analyzing one year crash data (including real-time weather and traffic variables) on I-70 in the state of Colorado. Additionally, the suggested method is also used to analyze single- and multi-vehicle crashes separately to identify their distinct characteristics. Compared with the traditional analysis methods, the proposed visible approach has the advantages of easy to be extended, transferred, and applied; easy to identify the effects of the various contributing factors on a traffic crash and to visually inspect the model. Moreover, the crash contributing factors identified in this study is beneficial for designing advanced early-warning and risk assessment systems in the context of real-time highway management. }
}
@article{Wang201322,
title = {Investigation of road network features and safety performance },
journal = {Accident Analysis & Prevention },
volume = {56},
number = {0},
pages = {22 - 31},
year = {2013},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2013.02.026},
url = {http://www.sciencedirect.com/science/article/pii/S0001457513000675},
author = {Xuesong Wang and Xingwei Wu and Mohamed Abdel-Aty and Paul J. Tremont},
keywords = {Road network structures},
keywords = {Safety performance},
keywords = {Traffic analysis zone},
keywords = {Meshedness Coefficient},
keywords = {Closeness Centrality},
keywords = {Betweenness Centrality},
keywords = {Bayesian Conditional Autoregressive model },
abstract = {The analysis of road network designs can provide useful information to transportation planners as they seek to improve the safety of road networks. The objectives of this study were to compare and define the effective road network indices and to analyze the relationship between road network structure and traffic safety at the level of the Traffic Analysis Zone (TAZ). One problem in comparing different road networks is establishing criteria that can be used to scale networks in terms of their structures. Based on data from Orange and Hillsborough Counties in Florida, road network structural properties within \{TAZs\} were scaled using 3 indices: Closeness Centrality, Betweenness Centrality, and Meshedness Coefficient. The Meshedness Coefficient performed best in capturing the structural features of the road network. Bayesian Conditional Autoregressive (CAR) models were developed to assess the safety of various network configurations as measured by total crashes, crashes on state roads, and crashes on local roads. The models’ results showed that crash frequencies on local roads were closely related to factors within the \{TAZs\} (e.g., zonal network structure, \{TAZ\} population), while crash frequencies on state roads were closely related to the road and traffic features of state roads. For the safety effects of different networks, the Grid type was associated with the highest frequency of crashes, followed by the Mixed type, the Loops & Lollipops type, and the Sparse type. This study shows that it is possible to develop a quantitative scale for structural properties of a road network, and to use that scale to calculate the relationships between network structural properties and safety. }
}
@article{Yu201351,
title = {Investigating different approaches to develop informative priors in hierarchical Bayesian safety performance functions },
journal = {Accident Analysis & Prevention },
volume = {56},
number = {0},
pages = {51 - 58},
year = {2013},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2013.03.023},
url = {http://www.sciencedirect.com/science/article/pii/S0001457513001218},
author = {Rongjie Yu and Mohamed Abdel-Aty},
keywords = {Informative prior},
keywords = {Bayesian inference},
keywords = {Hierarchical Bayesian model},
keywords = {Safety performance functions},
keywords = {Weather and traffic data },
abstract = {Abstract The Bayesian inference method has been frequently adopted to develop safety performance functions. One advantage of the Bayesian inference is that prior information for the independent variables can be included in the inference procedures. However, there are few studies that discussed how to formulate informative priors for the independent variables and evaluated the effects of incorporating informative priors in developing safety performance functions. This paper addresses this deficiency by introducing four approaches of developing informative priors for the independent variables based on historical data and expert experience. Merits of these informative priors have been tested along with two types of Bayesian hierarchical models (Poisson-gamma and Poisson-lognormal models). Deviance information criterion (DIC), R-square values, and coefficients of variance for the estimations were utilized as evaluation measures to select the best model(s). Comparison across the models indicated that the Poisson-gamma model is superior with a better model fit and it is much more robust with the informative priors. Moreover, the two-stage Bayesian updating informative priors provided the best goodness-of-fit and coefficient estimation accuracies. Furthermore, informative priors for the inverse dispersion parameter have also been introduced and tested. Different types of informative priors’ effects on the model estimations and goodness-of-fit have been compared and concluded. Finally, based on the results, recommendations for future research topics and study applications have been made. }
}
@article{Hassan201329,
title = {Predicting reduced visibility related crashes on freeways using real-time traffic flow data },
journal = {Journal of Safety Research },
volume = {45},
number = {0},
pages = {29 - 36},
year = {2013},
note = {},
issn = {0022-4375},
doi = {http://dx.doi.org/10.1016/j.jsr.2012.12.004},
url = {http://www.sciencedirect.com/science/article/pii/S0022437512001326},
author = {Hany M. Hassan and Mohamed A. Abdel-Aty},
keywords = {Real-time crash prediction},
keywords = {Freeways},
keywords = {Reduced visibility},
keywords = {Random Forests},
keywords = {Matched case-control logistic regression },
abstract = {AbstractObjectives The main objective of this paper is to investigate whether real-time traffic flow data, collected from loop detectors and radar sensors on freeways, can be used to predict crashes occurring at reduced visibility conditions. In addition, it examines the difference between significant factors associated with reduced visibility related crashes to those factors correlated with crashes occurring at clear visibility conditions. Method Random Forests and matched case-control logistic regression models were estimated. Results The findings indicated that real-time traffic variables can be used to predict visibility related crashes on freeways. The results showed that about 69% of reduced visibility related crashes were correctly identified. The results also indicated that traffic flow variables leading to visibility related crashes are slightly different from those variables leading to clear visibility crashes. Impact on Industry Using time slices 5–15 minutes before crashes might provide an opportunity for the appropriate traffic management centers for a proactive intervention to reduce crash risk in real-time. }
}
@article{Park2014167,
title = {Exploration and comparison of crash modification factors for multiple treatments on rural multilane roadways },
journal = {Accident Analysis & Prevention },
volume = {70},
number = {0},
pages = {167 - 177},
year = {2014},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2014.03.016},
url = {http://www.sciencedirect.com/science/article/pii/S0001457514000827},
author = {Juneyoung Park and Mohamed Abdel-Aty and Chris Lee},
keywords = {Safety effectiveness},
keywords = {Crash modification factors},
keywords = {Multiple treatments},
keywords = {Roadside elements},
keywords = {Highway Safety Manual },
abstract = {Abstract As multiple treatments (or countermeasures) are simultaneously applied to roadways, there is a need to assess their combined safety effects. Due to a lack of empirical crash modification factors (CMFs) for multiple treatments, the Highway Safety Manual (HSM) and other related studies developed various methods of combining multiple \{CMFs\} for single treatments. However, the literature did not evaluate the accuracy of these methods using \{CMFs\} obtained from the same study area. Thus, the main objectives of this research are: (1) develop \{CMFs\} for two single treatments (shoulder rumble strips, widening shoulder width) and one combined treatment (shoulder rumble strips + widening shoulder width) using before–after and cross-sectional methods and (2) evaluate the accuracy of the combined \{CMFs\} for multiple treatments estimated by the existing methods based on actual evaluated combined CMFs. Data was collected for rural multi-lane highways in Florida and four safety performance functions (SPFs) were estimated using 360 reference sites for two crash types (All crashes and Single Vehicle Run-off Roadway (SVROR) crashes) and two severity levels (all severity (KABCO) and injury (KABC)). The results of both before–after and cross-sectional methods show that the two single treatments and the combined treatment produced safety improvement. It was found that safety effects were higher for the roadway segments with shoulder rumble strips and wider shoulder width. It was also found that the treatments were more safety effective (i.e. lower CMF) for the roadway segments with narrower original shoulder width in the before period. However, although \{CMFs\} for multiple treatments were generally lower than \{CMFs\} for single treatments, they were similar for the roadway segments with shoulder width of 8–12 feet. More specifically, \{CMFs\} for single treatments were lower than \{CMFs\} for multiple treatments for the roadway segments with shoulder width of 9 feet or higher. Among different methods of combining CMFs, the HSM, Systematic Reduction of Subsequent CMFs, Applying only the most effective CMF, and Weighted average of multiple \{CMFs\} (Meta-Analysis) showed good estimates of the combined \{CMFs\} for multiple treatments with 2.2% difference between actual and estimated CMFs. The findings suggest that the existing methods of combining multiple \{CMFs\} are generally valid but they need to be applied for different crash types and injury levels separately. Lastly, an average of the combined \{CMFs\} from the best two methods was closer to the actual \{CMF\} than the combined \{CMF\} from only one best method. This indicates that it is better not to rely on only one specific existing method of combining \{CMFs\} for predicting \{CMF\} for multiple treatments. }
}
@article{Huang2014339,
title = {Indexing crash worthiness and crash aggressivity by major car brands },
journal = {Safety Science },
volume = {62},
number = {0},
pages = {339 - 347},
year = {2014},
note = {},
issn = {0925-7535},
doi = {http://dx.doi.org/10.1016/j.ssci.2013.09.002},
url = {http://www.sciencedirect.com/science/article/pii/S0925753513002105},
author = {Helai Huang and Shuiyan Hu and Mohamed Abdel-Aty},
keywords = {Crash compatibility},
keywords = {Crash worthiness},
keywords = {Crash aggressivity},
keywords = {Car brand},
keywords = {Car origin },
abstract = {Abstract This study aims at indexing the crash worthiness and crash aggressivity of 23 major car brands in Florida with consideration of the brand origin. It contributes to the literature by proposing a method for redefining the safety performance of cars by taking into account the cars’ hazardousness imposed on counterpart cars that are involved in the same crashes. A Bayesian hierarchical ordered logistic model was applied to relate the level of severity of drivers’ injuries to the crash compatibility of car brands. In the models, we assume that driver injury depends on the difference between the striking car’s aggressivity and the struck car’s self-protectiveness in two-vehicle crashes with external factors controlled. A total of 17,178 two-vehicle-crash records involving 34,356 cars in Florida were used in the investigation. The results show that most of the premium cars such as Volvo, Cadillac, Infiniti, and Lexus possess excellent crash worthiness and relatively low crash aggressivity. The self-protection abilities of popular car brands such as Ford, Toyota, Honda, and Chevrolet vary considerably, but have similar, below average hazardousness performances. European cars have relatively good self-protection but are also more hazardous to the counterpart cars when crashes occur. Japanese cars show lower worthiness and aggressivity than American cars, while South Korean cars are associated with the lowest crash worthiness and mean crash aggressivity. }
}
@article{Yu2013371,
title = {Bayesian random effect models incorporating real-time weather and traffic data to investigate mountainous freeway hazardous factors },
journal = {Accident Analysis & Prevention },
volume = {50},
number = {0},
pages = {371 - 376},
year = {2013},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2012.05.011},
url = {http://www.sciencedirect.com/science/article/pii/S0001457512001637},
author = {Rongjie Yu and Mohamed Abdel-Aty and Mohamed Ahmed},
keywords = {Mountainous freeway safety},
keywords = {Bayesian inference},
keywords = {Real-time weather data and random effect model },
abstract = {Freeway crash occurrences are highly influenced by geometric characteristics, traffic status, weather conditions and drivers’ behavior. For a mountainous freeway which suffers from adverse weather conditions, it is critical to incorporate real-time weather information and traffic data in the crash frequency study. In this paper, a Bayesian inference method was employed to model one year's crash data on I-70 in the state of Colorado. Real-time weather and traffic variables, along with geometric characteristics variables were evaluated in the models. Two scenarios were considered in this study, one seasonal and one crash type based case. For the methodology part, the Poisson model and two random effect models with a Bayesian inference method were employed and compared in this study. Deviance Information Criterion (DIC) was utilized as a comparison factor. The correlated random effect models outperformed the others. The results indicate that the weather condition variables, especially precipitation, play a key role in the crash occurrence models. The conclusions imply that different active traffic management strategies should be designed based on seasons, and single-vehicle crashes have different crash mechanism compared to multi-vehicle crashes. }
}
@article{Yu2013252,
title = {Utilizing support vector machine in real-time crash risk evaluation },
journal = {Accident Analysis & Prevention },
volume = {51},
number = {0},
pages = {252 - 259},
year = {2013},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2012.11.027},
url = {http://www.sciencedirect.com/science/article/pii/S0001457512004186},
author = {Rongjie Yu and Mohamed Abdel-Aty},
keywords = {Support vector machine model},
keywords = {Bayesian logistic regression},
keywords = {Real-time crash risk evaluation},
keywords = {Mountainous freeway safety },
abstract = {Real-time crash risk evaluation models will likely play a key role in Active Traffic Management (ATM). Models have been developed to predict crash occurrence in order to proactively improve traffic safety. Previous real-time crash risk evaluation studies mainly employed logistic regression and neural network models which have a linear functional form and over-fitting drawbacks, respectively. Moreover, these studies mostly focused on estimating the models but barely investigated the models’ predictive abilities. In this study, support vector machine (SVM), a recently proposed statistical learning model was introduced to evaluate real-time crash risk. The data has been split into a training dataset (used for developing the models) and scoring datasets (meant for assessing the models’ predictive power). Classification and regression tree (CART) model has been developed to select the most important explanatory variables and based on the results, three candidates Bayesian logistic regression models have been estimated with accounting for different levels unobserved heterogeneity. Then \{SVM\} models with different kernel functions have been developed and compared to the Bayesian logistic regression model. Model comparisons based on areas under the \{ROC\} curve (AUC) demonstrated that the \{SVM\} model with Radial-basis kernel function outperformed the others. Moreover, several extension analyses have been conducted to evaluate the effect of sample size on \{SVM\} models’ predictive capability; the importance of variable selection before developing \{SVM\} models; and the effect of the explanatory variables in the \{SVM\} models. Results indicate that (1) smaller sample size would enhance the \{SVM\} model's classification accuracy, (2) variable selection procedure is needed prior to the \{SVM\} model estimation, and (3) explanatory variables have identical effects on crash occurrence for the \{SVM\} models and logistic regression models. }
}
@article{Ahmed2013203,
title = {A data fusion framework for real-time risk assessment on freeways },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {26},
number = {0},
pages = {203 - 213},
year = {2013},
note = {},
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/j.trc.2012.09.002},
url = {http://www.sciencedirect.com/science/article/pii/S0968090X1200112X},
author = {Mohamed Ahmed and Mohamed Abdel-Aty},
keywords = {Freeway safety},
keywords = {Automatic Vehicle Identification},
keywords = {Remote Traffic Microwave Sensor},
keywords = {Data mining},
keywords = {Data fusion},
keywords = {Stochastic Gradient Boosting },
abstract = {The increased deployment of non-intrusive detection systems such as Automatic Vehicle Identification (AVI) and Remote Traffic Microwave Sensors (RTMSs) provides access to real-time traffic data from multiple sources. The availability of such rich data enhances the reliability of travel time estimation and route guidance systems, however, utilization of these data is absent in the context of proactive safety management systems. This paper presents a framework for real-time risk assessment on a freeway in Colorado by fusing data from two different detection systems (AVI and RTMS), real-time weather and roadway geometry. Stochastic Gradient Boosting (SGB), a relatively recent and promising machine learning technique is used to calibrate the models. SGB’s key strengths lie in its capability to fit complex nonlinear relationships, handling different types of predictors (nominal and categorical) and accommodating missing values with no need for prior transformation of the predictor variables or elimination of outliers. Boosting multiple simple trees together overcomes the drawback of single tree models of poor prediction accuracy and provides fast and superior predictive performance. The proposed framework is considered a good alternative for real-time risk assessment on freeways because of its high estimation accuracy, robustness and reliability. }
}
@article{AbdelAty2012288,
title = {Real-time prediction of visibility related crashes },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {24},
number = {0},
pages = {288 - 298},
year = {2012},
note = {},
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/j.trc.2012.04.001},
url = {http://www.sciencedirect.com/science/article/pii/S0968090X12000514},
author = {Mohamed A. Abdel-Aty and Hany M. Hassan and Mohamed Ahmed and Ali S. Al-Ghamdi},
keywords = {Real-time crash risk},
keywords = {Loop/radar detectors},
keywords = {Automatic vehicle identification},
keywords = {Reduced visibility},
keywords = {Bayesian matched case-control logistic regression },
abstract = {More researchers started using real-time traffic surveillance data, collected from loop/radar detectors (LDs), for proactive crash risk assessment. However, there is a lack of prior studies that investigated the link between real-time traffic data and crash risk of reduced visibility related (VR) crashes. Two issues that have not explicitly been addressed in prior studies are; (1) the possibility of predicting \{VR\} crashes using traffic data collected from the Automatic Vehicle Identification (AVI) sensors installed on Expressways and (2) which traffic data are advantageous for predicting \{VR\} crashes; \{LDs\} or AVIs. Thus, this study attempts to examine the relationships between \{VR\} crash risk and real-time traffic data collected from \{LDs\} installed on two Freeways in Central Florida (I-4 and I-95) and from \{AVI\} sensors installed on two Expressways (SR 408 and \{SR\} 417). Also, it investigates which data are better for predicting \{VR\} crashes. The approach adopted here involves developing Bayesian matched case-control logistic regression models using the historical crashes, \{LDs\} and \{AVI\} data. Regarding the model estimated based on \{LDs\} data, the average speed observed at the nearest downstream station along with the coefficient of variation in speed observed at the nearest upstream station, all at 5–10 min prior to the crash time, were found to have significant effect on \{VR\} crash risk. However, for the model developed based on \{AVI\} data, the coefficient of variation in speed observed at the crash segment, at 5–10 min prior to the crash time, affected the likelihood of \{VR\} crash occurrence. The results showed that both \{LDs\} and \{AVI\} systems can be used for safety application (i.e., predicting \{VR\} crashes). It was found that up to 73% of \{VR\} crashes could be identified correctly. Argument concerning which traffic data (LDs or AVI) are better for predicting \{VR\} crashes is also provided and discussed. }
}
@article{Jiang201474,
title = {Application of Poisson random effect models for highway network screening },
journal = {Accident Analysis & Prevention },
volume = {63},
number = {0},
pages = {74 - 82},
year = {2014},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2013.10.029},
url = {http://www.sciencedirect.com/science/article/pii/S0001457513004399},
author = {Ximiao Jiang and Mohamed Abdel-Aty and Samer Alamili},
keywords = {Hotspot identification},
keywords = {Network screening},
keywords = {Empirical Bayesian},
keywords = {Full Bayesian},
keywords = {Random effect},
keywords = {Poisson Log-Normal },
abstract = {Abstract In recent years, Bayesian random effect models that account for the temporal and spatial correlations of crash data became popular in traffic safety research. This study employs random effect Poisson Log-Normal models for crash risk hotspot identification. Both the temporal and spatial correlations of crash data were considered. Potential for Safety Improvement (PSI) were adopted as a measure of the crash risk. Using the fatal and injury crashes that occurred on urban 4-lane divided arterials from 2006 to 2009 in the Central Florida area, the random effect approaches were compared to the traditional Empirical Bayesian (EB) method and the conventional Bayesian Poisson Log-Normal model. A series of method examination tests were conducted to evaluate the performance of different approaches. These tests include the previously developed site consistence test, method consistence test, total rank difference test, and the modified total score test, as well as the newly proposed total safety performance measure difference test. Results show that the Bayesian Poisson model accounting for both temporal and spatial random effects (PTSRE) outperforms the model that with only temporal random effect, and both are superior to the conventional Poisson Log-Normal model (PLN) and the \{EB\} model in the fitting of crash data. Additionally, the method evaluation tests indicate that the \{PTSRE\} model is significantly superior to the \{PLN\} model and the \{EB\} model in consistently identifying hotspots during successive time periods. The results suggest that the \{PTSRE\} model is a superior alternative for road site crash risk hotspot identification. }
}
@article{Huang20111364,
title = {Indexing crash worthiness and crash aggressivity by vehicle type },
journal = {Accident Analysis & Prevention },
volume = {43},
number = {4},
pages = {1364 - 1370},
year = {2011},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2011.02.010},
url = {http://www.sciencedirect.com/science/article/pii/S0001457511000248},
author = {Helai Huang and Chowdhury Siddiqui and Mohamed Abdel-Aty},
keywords = {Crash compatibility},
keywords = {Crash worthiness},
keywords = {Crash aggressivity},
keywords = {Bayesian hierarchical model},
keywords = {Ordered logistic model },
abstract = {Crash aggressivity (CA), along with conventional crash worthiness (CW), has been recently studied to deal with the crash incompatibility between vehicles on roads. Clearly, injury severity depends on the attacking ability of striking vehicle as well as the protective ability of struck vehicle. This study proposes a systematic crash-based approach to index \{CA\} and \{CW\} of various vehicles. The approach deviates from existing methods in three aspects: (a) an explicit definition and specification in the model for \{CW\} and CA; (b) Bayesian hierarchical analysis to account for the crash-vehicle two-level data structure; (c) a five-level ordinal model to explicitly consider all levels of crash severity. The case study on major vehicle types illustrated the method and confirmed the consistency of results with previous studies. Both crash worthiness and crash aggressivity significantly vary by vehicle types, in which we identified the dominating effect of vehicle mass, and also highlighted the extraordinary aggressivity of Light Trucks and Vans (LTVs). While it was not surprising to identify least \{CA\} and \{CW\} of motorcycles, buses were unconventionally found to be less aggressive than other motor vehicles. The method proposed in this research is applicable to detailed crash-based vehicle inspection and evaluation. }
}
@article{Siddiqui2012317,
title = {Aggregate nonparametric safety analysis of traffic zones },
journal = {Accident Analysis & Prevention },
volume = {45},
number = {0},
pages = {317 - 325},
year = {2012},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2011.07.019},
url = {http://www.sciencedirect.com/science/article/pii/S0001457511002168},
author = {Chowdhury Siddiqui and Mohamed Abdel-Aty and Helai Huang},
keywords = {Macro-level safety analysis},
keywords = {Total crash},
keywords = {Severe crash},
keywords = {Data mining},
keywords = {Random forest},
keywords = {Safety planning },
abstract = {Exploring the significant variables related to specific types of crashes is vitally important in the planning stage of a transportation network. This paper aims to identify and examine important variables associated with total crashes and severe crashes per traffic analysis zone (TAZ) in four counties of the state of Florida by applying nonparametric statistical techniques such as data mining and random forest. The intention of investigating these factors in such aggregate level analysis is to incorporate proactive safety measures in transportation planning. Total and severe crashes per \{TAZ\} were modeled to provide predictive decision trees. The variables which carried higher weight of importance for total crashes per \{TAZ\} were – total number of intersections per TAZ, airport trip productions, light truck productions, and total roadway segment length with 35 mph posted speed limit. The other significant variables identified for total crashes were total roadway length with 15 mph posted speed limit, total roadway length with 65 mph posted speed limit, and non-home based work productions. For severe crashes, total number of intersections per TAZ, light truck productions, total roadway length with 35 mph posted speed limit, and total roadway length with 65 mph posted speed limit were among the significant variables. These variables were further verified and supported by the random forest results. }
}
@article{AbdelAty201362,
title = {Geographical unit based analysis in the context of transportation safety planning },
journal = {Transportation Research Part A: Policy and Practice },
volume = {49},
number = {0},
pages = {62 - 75},
year = {2013},
note = {},
issn = {0965-8564},
doi = {http://dx.doi.org/10.1016/j.tra.2013.01.030},
url = {http://www.sciencedirect.com/science/article/pii/S0965856413000372},
author = {Mohamed Abdel-Aty and Jaeyoung Lee and Chowdhury Siddiqui and Keechoo Choi},
keywords = {Macro-level analysis},
keywords = {Bayesian Poisson log-normal model},
keywords = {Transportation safety planning},
keywords = {Traffic analysis zones },
abstract = {A wide array of spatial units has been explored in macro-level modeling. With the advancement of Geographic Information System (GIS) analysts are able to analyze crashes for various geographical units. However, a clear guideline on which geographic entity should be chosen is not present. Macro level safety analysis is at the core of transportation safety planning (TSP) which in turn is a key in many aspects of policy and decision making of safety investments. The preference of spatial unit can vary with the dependent variable of the model. Or, for a specific dependent variable, models may be invariant to multiple spatial units by producing a similar goodness-of-fits. In this study three different crash models were investigated for traffic analysis zones (TAZs), block groups (BGs) and census tracts (CTs) of two counties in Florida. The models were developed for the total crashes, severe crashes and pedestrian crashes in this region. The primary objective of the study was to explore and investigate the effect of zonal variation (scale and zoning) on these specific types of crash models. These models were developed based on various roadway characteristics and census variables (e.g., land use, socio-economic, etc.). It was found that the significance of explanatory variables is not consistent among models based on different zoning systems. Although the difference in variable significance across geographic units was found, the results also show that the sign of the coefficients are reasonable and explainable in all models. Key findings of this study are, first, signs of coefficients are consistent if these variables are significant in models with same response variables, even if geographic units are different. Second, the number of significant variables is affected by response variables and also geographic units. Admittedly, \{TAZs\} are now the only traffic related zone system, thus \{TAZs\} are being widely used by transportation planners and frequently utilized in research related to macroscopic crash analysis. Nevertheless, considering that \{TAZs\} are not delineated for traffic crash analysis but they were designed for the long range transportation plans, \{TAZs\} might not be the optimal zone system for traffic crash modeling at the macroscopic level. Therefore, it recommended that other zone systems be explored for crash analysis as well. }
}
@article{Dixit20111610,
title = {Quality of traffic flow on urban arterial streets and its relationship with safety },
journal = {Accident Analysis & Prevention },
volume = {43},
number = {5},
pages = {1610 - 1616},
year = {2011},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2011.01.006},
url = {http://www.sciencedirect.com/science/article/pii/S0001457511000078},
author = {Vinayak V. Dixit and Anurag Pande and Mohamed Abdel-Aty and Abhishek Das and Essam Radwan},
keywords = {Two-fluid model},
keywords = {Driver behavior},
keywords = {Arterials},
keywords = {Surrogate safety measures },
abstract = {The two-fluid model for vehicular traffic flow explains the traffic on arterials as a mix of stopped and running vehicles. It describes the relationship between the vehicles’ running speed and the fraction of running vehicles. The two parameters of the model essentially represent ‘free flow’ travel time and level of interaction among vehicles, and may be used to evaluate urban roadway networks and urban corridors with partially limited access. These parameters are influenced by not only the roadway characteristics but also by behavioral aspects of driver population, e.g., aggressiveness. Two-fluid models are estimated for eight arterial corridors in Orlando, \{FL\} for this study. The parameters of the two-fluid model were used to evaluate corridor level operations and the correlations of these parameters’ with rates of crashes having different types/severity. Significant correlations were found between two-fluid parameters and rear-end and angle crash rates. Rate of severe crashes was also found to be significantly correlated with the model parameter signifying inter-vehicle interactions. While there is need for further analysis, the findings suggest that the two-fluid model parameters may have potential as surrogate measures for traffic safety on urban arterial streets. }
}
@article{Park20111267,
title = {A stochastic catastrophe model using two-fluid model parameters to investigate traffic safety on urban arterials },
journal = {Accident Analysis & Prevention },
volume = {43},
number = {3},
pages = {1267 - 1278},
year = {2011},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2011.01.009},
url = {http://www.sciencedirect.com/science/article/pii/S0001457511000108},
author = {Peter Y. Park and Mohamed Abdel-Aty},
keywords = {Catastrophe model},
keywords = {Urban arterials},
keywords = {Two-fluid model},
keywords = {Pro-active safety },
abstract = {During the last few decades, the two-fluid model and its two parameters have been widely used in transportation engineering to represent the quality of operational traffic service on urban arterials. Catastrophe models have also often been used to describe traffic flow on freeway sections. This paper demonstrates the possibility of developing a pro-active network screening tool that estimates the crash rate using a stochastic cusp catastrophe model with the two-fluid model's parameters as inputs. The paper investigates the analogy in logic behind the two-fluid model and the catastrophe model using straightforward graphical illustrations. The paper then demonstrates the application of two-fluid model parameters to a stochastic catastrophe model designed to estimate the level of safety on urban arterials. Current road safety management, including network safety screening, is post-active rather than pro-active in the sense that an existing hotspot must be identified before a safety improvement program can be implemented. This paper suggests that a stochastic catastrophe model can help us to become more pro-active by helping us to identify urban arterials that currently show an acceptable level of safety, but which are vulnerable to turning into crash hotspots. We would then be able to implement remedial actions before hotspots develop. }
}
@article{Ahmed20111581,
title = {Exploring a Bayesian hierarchical approach for developing safety performance functions for a mountainous freeway },
journal = {Accident Analysis & Prevention },
volume = {43},
number = {4},
pages = {1581 - 1589},
year = {2011},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2011.03.021},
url = {http://www.sciencedirect.com/science/article/pii/S0001457511000728},
author = {Mohamed Ahmed and Helai Huang and Mohamed Abdel-Aty and Bernardo Guevara},
keywords = {Safety},
keywords = {Freeway},
keywords = {Adverse weather},
keywords = {Slope},
keywords = {Curve},
keywords = {Bayesian model },
abstract = {While rural freeways generally have lower crash rates, interactions between driver behavior, traffic and geometric characteristics, and adverse weather conditions may increase the crash risk along some freeway sections. This paper examines the safety effects of roadway geometrics on crash occurrence along a freeway section that features mountainous terrain and adverse weather. Starting from preliminary exploration using Poisson models, Bayesian hierarchical models with spatial and random effects were developed to efficiently model the crash frequencies on road segments on the 20-mile freeway section of study. Crash data for 6 years (2000–2005), roadway geometry, traffic characteristics and weather information in addition to the effect of steep slopes and adverse weather of snow and dry seasons, were used in the investigation. Estimation of the model coefficients indicates that roadway geometry is significantly associated with crash risk; segments with steep downgrades were found to drastically increase the crash risk. Moreover, this crash risk could be significantly increased during snow season compared to dry season as a confounding effect between grades and pavement condition. Moreover, sites with higher degree of curvature, wider medians and an increase of the number of lanes appear to be associated with lower crash rate. Finally, a Bayesian ranking technique was implemented to rank the hazard levels of the roadway segments; the results confirmed that segments with steep downgrades are more crash prone along the study section. }
}
@article{AbdelAty2007581,
title = {Crash data analysis: Collective vs. individual crash level approach },
journal = {Journal of Safety Research },
volume = {38},
number = {5},
pages = {581 - 587},
year = {2007},
note = {},
issn = {0022-4375},
doi = {http://dx.doi.org/10.1016/j.jsr.2007.04.007},
url = {http://www.sciencedirect.com/science/article/pii/S0022437507001065},
author = {Mohamed Abdel-Aty and Anurag Pande},
keywords = {Traffic safety},
keywords = {Crash data analysis},
keywords = {Black-spots},
keywords = {Crash frequency},
keywords = {Real-time crash likelihood },
abstract = {Introduction Traffic safety literature has traditionally focused on identification of location profiles where “more crashes are likely to occur” over a period of time. The analysis involves estimation of crash frequency and/or rate (i.e., frequency normalized based on some measure of exposure) with geometric design features (e.g., number of lanes) and traffic characteristics (e.g., Average Annual Daily Traffic [AADT]) of the roadway location. In the recent past, a new category of traffic safety studies has emerged, which attempts to identify locations where a “crash is more likely to occur.” The distinction between the two groups of studies is that the latter group of locations would change based on the varying traffic patterns over the course of the day or even within the hour. Method Hence, instead of estimation of crash frequency over a period of time, the objective becomes real-time estimation of crash likelihood. The estimation of real-time crash likelihood has a traffic management component as well. It is a proactive extension to the traditional approach of incident detection, which involves analysis of traffic data recorded immediately after the incident. The units of analysis used in these studies are individual crashes rather than counts of crashes. Results In this paper, crash data analysis based on the two approaches, collective and at individual crash level, is discussed along with the advantages and shortcomings of the two approaches. }
}
@article{Das2009317,
title = {Using conditional inference forests to identify the factors affecting crash severity on arterial corridors },
journal = {Journal of Safety Research },
volume = {40},
number = {4},
pages = {317 - 327},
year = {2009},
note = {},
issn = {0022-4375},
doi = {http://dx.doi.org/10.1016/j.jsr.2009.05.003},
url = {http://www.sciencedirect.com/science/article/pii/S0022437509000693},
author = {Abhishek Das and Mohamed Abdel-Aty and Anurag Pande},
keywords = {Multilane arterials},
keywords = {Severe crashes},
keywords = {Crash types},
keywords = {Conditional inference trees and forests},
keywords = {Classification trees },
abstract = {Introduction The study aims at identifying traffic/highway design/driver-vehicle information significantly related with fatal/severe crashes on urban arterials for different crash types. Since the data used in this study are observational (i.e., collected outside the purview of a designed experiment), an information discovery approach is adopted for this study. Method Random Forests, which are ensembles of individual trees grown by \{CART\} (Classification and Regression Tree) algorithm, are applied in numerous applications for this purpose. Specifically, conditional inference forests have been implemented. In each tree of the conditional inference forest, splits are based on how good the association is. Chi-square test statistics are used to measure the association. Apart from identifying the variables that improve classification accuracy, the methodology also clearly identifies the variables that are neutral to accuracy, and also those that decrease it. Results The methodology is quite insightful in identifying the variables of interest in the database (e.g., alcohol/ drug use and higher posted speed limits contribute to severe crashes). Failure to use safety equipment by all passengers and presence of driver/passenger in the vulnerable age group (more than 55 years or less than 3 years) increased the severity of injuries given a crash had occurred. A new variable, ‘element’ has been used in this study, which assigns crashes to segments, intersections, or access points based on the information from site location, traffic control, and presence of signals. Impact The authors were able to identify roadway locations where severe crashes tend to occur. For example, segments and access points were found to be riskier for single vehicle crashes. Higher skid resistance and k-factor also contributed toward increased severity of injuries in crashes. }
}
@article{Pande2010391,
title = {A classification tree based modeling approach for segment related crashes on multilane highways },
journal = {Journal of Safety Research },
volume = {41},
number = {5},
pages = {391 - 397},
year = {2010},
note = {},
issn = {0022-4375},
doi = {http://dx.doi.org/10.1016/j.jsr.2010.06.004},
url = {http://www.sciencedirect.com/science/article/pii/S0022437510000757},
author = {Anurag Pande and Mohamed Abdel-Aty and Abhishek Das},
keywords = {Crash frequency},
keywords = {Arterial safety},
keywords = {Classification trees},
keywords = {Mid-block segment crashes },
abstract = {Introduction This study presents a classification tree based alternative to crash frequency analysis for analyzing crashes on mid-block segments of multilane arterials. Method The traditional approach of modeling counts of crashes that occur over a period of time works well for intersection crashes where each intersection itself provides a well-defined unit over which to aggregate the crash data. However, in the case of mid-block segments the crash frequency based approach requires segmentation of the arterial corridor into segments of arbitrary lengths. In this study we have used random samples of time, day of week, and location (i.e., milepost) combinations and compared them with the sample of crashes from the same arterial corridor. For crash and non-crash cases, geometric design/roadside and traffic characteristics were derived based on their milepost locations. The variables used in the analysis are non-event specific and therefore more relevant for roadway safety feature improvement programs. First classification tree model is a model comparing all crashes with the non-crash data and then four groups of crashes (rear-end, lane-change related, pedestrian, and single-vehicle/off-road crashes) are separately compared to the non-crash cases. The classification tree models provide a list of significant variables as well as a measure to classify crash from non-crash cases. \{ADT\} along with time of day/day of week are significantly related to all crash types with different groups of crashes being more likely to occur at different times. Conclusions From the classification performance of different models it was apparent that using non-event specific information may not be suitable for single vehicle/off-road crashes. Impact on Industry The study provides the safety analysis community an additional tool to assess safety without having to aggregate the corridor crash data over arbitrary segment lengths. }
}
@article{Das2010548,
title = {A genetic programming approach to explore the crash severity on multi-lane roads },
journal = {Accident Analysis & Prevention },
volume = {42},
number = {2},
pages = {548 - 557},
year = {2010},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2009.09.021},
url = {http://www.sciencedirect.com/science/article/pii/S0001457509002590},
author = {Abhishek Das and Mohamed Abdel-Aty},
keywords = {Crash severity},
keywords = {Multi-lane roads},
keywords = {Genetic algorithm},
keywords = {Genetic programming},
keywords = {Discipulus },
abstract = {The study aims at understanding the relationship of geometric and environmental factors with injury related crashes as well as with severe crashes through the development of classification models. The Linear Genetic Programming (LGP) method is used to achieve these objectives. \{LGP\} is based on the traditional genetic algorithm, except that it evolves computer programs. The methodology is different from traditional non-parametric methods like classification and regression trees which develop only one model, with fixed criteria, for any given dataset. The \{LGP\} on the other hand not only evolves numerous models through the concept of biological evolution, and using the evolutionary operators of crossover and mutation, but also allows the investigator to choose the best models, developed over various runs, based on classification rates. Discipulus™ software was used to evolve the models. The results included vision obstruction which was found to be a leading factor for severe crashes. Percentage of trucks, even if small, is more likely to make the crashes injury prone. The ‘lawn and curb’ median are found to be safe for angle/turning movement crashes. Dry surface conditions as well as good pavement conditions decrease the severity of crashes and so also wider shoulder and sidewalk widths. Interaction terms among variables like on-street parking with higher posted speed limit have been found to make injuries more probable. }
}
@article{Wang20081674,
title = {Analysis of left-turn crash injury severity by conflicting pattern using partial proportional odds models },
journal = {Accident Analysis & Prevention },
volume = {40},
number = {5},
pages = {1674 - 1682},
year = {2008},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2008.06.001},
url = {http://www.sciencedirect.com/science/article/pii/S0001457508000948},
author = {Xuesong Wang and Mohamed Abdel-Aty},
keywords = {Signalized intersection},
keywords = {Left-turn crash},
keywords = {Conflicting pattern},
keywords = {Crash injury severity},
keywords = {Partial proportional odds model},
keywords = {Significant factor },
abstract = {The purpose of this study is to examine left-turn crash injury severity. Left-turning traffic colliding with opposing through traffic and with near-side through traffic are the two most frequently occurring conflicting patterns among left-turn crashes (Patterns 5 and 8 in the paper, respectively), and they are prone to be severe. Ordered probability models with either logit or probit function is commonly applied in crash injury severity analyses; however, its critical assumption that the slope coefficients do not vary over different alternatives except the cut-off points is usually too restrictive. Partial proportional odds models are generalizations of ordered probability models, for which some of the beta coefficients can differ across alternatives, were applied to investigate Patterns 5 and 8, and the total left-turn crash injuries. The results show that partial proportional odds models consistently perform better than ordered probability models. By focusing on specific conflicting patterns, locating crashes to the exact crash sites and relating approach variables to crash injury in the analysis, researchers are able to investigate how these variables affect left-turn crash injuries. For example, opposing through traffic and near-side crossing through traffic in the hour of collision were identified significant for Patterns 5 and 8 crash injuries, respectively. Protected left-turn phasing is significantly correlated with Pattern 5 crash injury. Many other variables in driver attributes, vehicular characteristics, roadway geometry design, environmental factors, and crash characteristics were identified. Specifically, the use of the partial proportional formulation allows a much better identification of the increasing effect of alcohol and/or drug use on crash injury severity, which previously was masked using the conventional ordered probability models. }
}
@article{Huang20101556,
title = {Multilevel data and Bayesian analysis in traffic safety },
journal = {Accident Analysis & Prevention },
volume = {42},
number = {6},
pages = {1556 - 1565},
year = {2010},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2010.03.013},
url = {http://www.sciencedirect.com/science/article/pii/S0001457510000953},
author = {Helai Huang and Mohamed Abdel-Aty},
keywords = {Road safety},
keywords = {Crash prediction models},
keywords = {Bayesian hierarchical models},
keywords = {Multilevel data},
keywords = {Spatiotemporal data },
abstract = {Background Traditional crash prediction models, such as generalized linear regression model, are incapable of taking into account multilevel data structure. Therefore they suffer from a common underlying limitation that each observation (e.g. a crash or a vehicle involvement) in the estimation procedure corresponds to an individual situation in which the residuals exhibit independence. Problem However, this “independence” assumption may often not hold true since multilevel data structures exist extensively because of the traffic data collection and clustering process. Disregarding the possible within-group correlations may lead to production of models with unreliable parameter estimates and statistical inferences. Proposed theory In this paper, a 5 × ST-level hierarchy is proposed to represent the general framework of multilevel data structures in traffic safety, i.e. [Geographic region level − Traffic site level − Traffic crash level − Driver-vehicle unit level − Occupant level] × Spatiotemporal level. The involvement and emphasis for different sub-groups of these levels depend on different research purposes and also rely on the heterogeneity examination on crash data employed. To properly accommodate the potential cross-group heterogeneity and spatiotemporal correlation due to the multilevel data structure, a Bayesian hierarchical approach that explicitly specifies multilevel structure and reliably yields parameter estimates is introduced and recommended. Case studies Using Bayesian hierarchical models, the results from several case studies are highlighted to show the improvements on model fitting and predictive performance over traditional models by appropriately accounting for the multilevel data structure. }
}
@article{Siddiqui2012382,
title = {Macroscopic spatial analysis of pedestrian and bicycle crashes },
journal = {Accident Analysis & Prevention },
volume = {45},
number = {0},
pages = {382 - 391},
year = {2012},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2011.08.003},
url = {http://www.sciencedirect.com/science/article/pii/S0001457511002235},
author = {Chowdhury Siddiqui and Mohamed Abdel-Aty and Keechoo Choi},
keywords = {Pedestrian crashes},
keywords = {Bicycle crashes},
keywords = {Spatial analysis},
keywords = {Traffic Analysis Zones},
keywords = {Bayesian analysis },
abstract = {This study investigates the effect of spatial correlation using a Bayesian spatial framework to model pedestrian and bicycle crashes in Traffic Analysis Zones (TAZs). Aggregate models for pedestrian and bicycle crashes were estimated as a function of variables related to roadway characteristics, and various demographic and socio-economic factors. It was found that significant differences were present between the predictor sets for pedestrian and bicycle crashes. The Bayesian Poisson-lognormal model accounting for spatial correlation for pedestrian crashes in the \{TAZs\} of the study counties retained nine variables significantly different from zero at 95% Bayesian credible interval. These variables were – total roadway length with 35 mph posted speed limit, total number of intersections per TAZ, median household income, total number of dwelling units, log of population per square mile of a TAZ, percentage of households with non-retired workers but zero auto, percentage of households with non-retired workers and one auto, long term parking cost, and log of total number of employment in a TAZ. A separate distinct set of predictors were found for the bicycle crash model. In all cases the Bayesian models with spatial correlation performed better than the models that did not account for spatial correlation among TAZs. This finding implies that spatial correlation should be considered while modeling pedestrian and bicycle crashes at the aggregate or macro-level. }
}
@article{Hassan2013361,
title = {Exploring the safety implications of young drivers’ behavior, attitudes and perceptions },
journal = {Accident Analysis & Prevention },
volume = {50},
number = {0},
pages = {361 - 370},
year = {2013},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2012.05.003},
url = {http://www.sciencedirect.com/science/article/pii/S0001457512001558},
author = {Hany M. Hassan and Mohamed A. Abdel-Aty},
keywords = {Crash risk},
keywords = {Young drivers’ behavior},
keywords = {Structural equation modeling },
abstract = {The present study aims at identifying and quantifying significant factors (i.e., demographic, aberrant driving behavior) associated with young drivers’ involvement in at-fault crashes or traffic citations at the ages of 16–17 (while having the Operational License) and 18–24 years old (while having the Full License). A second objective was to investigate the main reason(s) for involvement in risky driving behavior by young drivers. The data used for the analyses were obtained from a self-reported questionnaire survey carried out among 680 young drivers in Central Florida. To achieve these goals, the structural equation modeling approach was adopted. The results revealed that aggressive violations, in-vehicle distractions and demographic characteristics were the significant factors affecting young drivers’ involvement in at-fault crashes or traffic violations at the age of 16–17. However, in-vehicle distractions, attitudes toward speeding and demographic characteristics were the significant factors affecting young drivers’ crash risk at 18–24. Additionally, the majority of participants reported that “running late” is the main reason for taking risk while driving (i.e., speeding, accept short gaps, or drive so close to the car in front) followed by “racing other cars”. Additionally, “exceed speed limits” was the main reason for receiving traffic citations at 16–17 and 18–24 age groups. Practical suggestions on how to reduce crash risk and promote safe driving among young drivers are also discussed. }
}
@article{Hassan2011614,
title = {Analysis of drivers’ behavior under reduced visibility conditions using a Structural Equation Modeling approach },
journal = {Transportation Research Part F: Traffic Psychology and Behaviour },
volume = {14},
number = {6},
pages = {614 - 625},
year = {2011},
note = {Special Issue: Driving Simulation in Traffic Psychology },
issn = {1369-8478},
doi = {http://dx.doi.org/10.1016/j.trf.2011.07.002},
url = {http://www.sciencedirect.com/science/article/pii/S1369847811000696},
author = {Hany M. Hassan and Mohamed A. Abdel-Aty},
keywords = {Drivers’ behavior},
keywords = {Reduced visibility},
keywords = {Warning messages},
keywords = {Changeable message signs},
keywords = {Variable speed limit signs},
keywords = {Structural Equation Modeling },
abstract = {One way to improve safety under reduced visibility conditions (i.e., reduce the chances of visibility related crashes) is to improve drivers’ behavior under such adverse weather conditions. The aim of this paper is to thoroughly examine drivers’ responses under low visibility conditions and quantify the impacts and values of various factors found to be related to drivers’ compliance and drivers’ satisfaction with variable speed limit (VSL) and changeable message signs (CMS) instructions in different visibility, traffic conditions, and on two types of roadways; freeways and two-lane roads. The data used for the analyses were obtained from a self-reported questionnaire survey carried out among 566 drivers in Central Florida, USA. To achieve these goals, Explanatory Factor Analysis (EFA) and Structural Equation Modeling (SEM) approaches were adopted. The results revealed that drivers’ satisfaction with VSL/CMS was the most significant factor that positively affected drivers’ compliance with advice or warning messages displayed on VSL/CMS under different fog conditions followed by human factors. Moreover, it was found that roadway type affected drivers’ compliance to \{VSL\} instructions under medium and heavy fog conditions. Furthermore, drivers’ familiarity with \{VSL\} and human factors were the significant factors affecting drivers’ satisfaction with VSL/CMS advice under reduced visibility conditions. Based on the findings of the present study, several recommendations are suggested as guidelines to improve drivers’ behavior in such reduced visibility conditions by enhancing drivers’ compliance with VSL/CMS instructions. }
}
@article{Pande2009985,
title = {A novel approach for analyzing severe crash patterns on multilane highways },
journal = {Accident Analysis & Prevention },
volume = {41},
number = {5},
pages = {985 - 994},
year = {2009},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2009.06.003},
url = {http://www.sciencedirect.com/science/article/pii/S0001457509001183},
author = {Anurag Pande and Mohamed Abdel-Aty},
keywords = {Multilane highways},
keywords = {Traffic safety},
keywords = {Severe crashes},
keywords = {Matched sampling },
abstract = {This study presents a novel approach for analysis of patterns in severe crashes that occur on mid-block segments of multilane highways with partially limited access. A within stratum matched crash vs. non-crash classification approach is adopted towards that end. Under this approach crashes serve as units of analysis and it does not require aggregation of crash data over arterial segments of arbitrary lengths. Also, the proposed approach does not use information on non-severe crashes and hence is not affected by under-reporting of the minor crashes. Random samples of time, day of week, and location (i.e., milepost) combinations were collected for multilane arterials in the state of Florida and matched with severe crashes from the corresponding corridor to form matched strata consisting of severe crash and non-crash cases. For these cases, geometric design/roadside and traffic characteristics were derived based on the corresponding milepost locations. Four groups of crashes, severe rear-end, lane-change related, pedestrian, and single-vehicle/off-road crashes, on multilane arterials segments were compared separately to the non-crash cases. Severe lane-change related crashes may primarily be attributed to exposure while single-vehicle crashes and pedestrian crashes have no significant relationship with the \{ADT\} (Average Daily Traffic). For severe rear-end crashes speed limit, ADT, K-factor, time of day/day of week, median type, pavement condition, and presence of horizontal curvature were significant factors. The proposed approach uses general roadway characteristics as independent variables rather than event-specific information (i.e., crash characteristics such as driver/vehicle details); it has the potential to fit within a safety evaluation framework for arterial segments. }
}
@article{Wang2011682,
title = {Design and verification of a laser based device for pavement macrotexture measurement },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {19},
number = {4},
pages = {682 - 694},
year = {2011},
note = {},
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/j.trc.2010.12.001},
url = {http://www.sciencedirect.com/science/article/pii/S0968090X10001646},
author = {Weifeng Wang and Xinping Yan and Helai Huang and Xiumin Chu and Mohamed Abdel-Aty},
keywords = {Road surface},
keywords = {Pavement management},
keywords = {Texture profile},
keywords = {Macrotexture measuring device},
keywords = {Laser technique },
abstract = {Pavement surface macrotexture greatly contributes to tire-pavement skid resistance which has a direct effect on traffic operation and safety particularly at high speeds. Therefore, efforts are needed to develop effective and practical devices to measure macrotexture profile. In this study, a practical laser device was developed, which is lightweight and portable with low cost. Following a critical review on existing devices, this paper outlines the hardware and software configurations of the proposed system. A comprehensive illustration on how the system works is presented to show a number of merits associated with the proposed device and accompanying analysis programs. Results from pilot testing experiments confirm that the proposed system provides efficient, reliable, accurate and consistent measurements for pavement surface profiles. }
}
@article{AbdelAty20111730,
title = {A study on crashes related to visibility obstruction due to fog and smoke },
journal = {Accident Analysis & Prevention },
volume = {43},
number = {5},
pages = {1730 - 1737},
year = {2011},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2011.04.003},
url = {http://www.sciencedirect.com/science/article/pii/S0001457511000844},
author = {Mohamed Abdel-Aty and Al-Ahad Ekram and Helai Huang and Keechoo Choi},
keywords = {Fog and smoke},
keywords = {Visibility},
keywords = {Crash risk},
keywords = {Injury severity },
abstract = {Research on weather effects has focused on snow- or rain-related crashes. However, there is a lack of understanding of crashes that occur during fog or smoke (FS). This study presents a comprehensive examination of FS-related crashes using crash data from Florida between 2003 and 2007. A two-stage research strategy was implemented (1) to examine FS-related crash characteristics with respect to temporal distribution, influential factors and crash types and (2) to estimate the effects of various factors on injury severity given that a FS-related crash has occurred. The morning hours from December to February are the prevalent times for FS-related crashes. Compared to crashes under clear-visibility conditions, FS-related crashes tend to result in more severe injuries and involve more vehicles. Head-on and rear-end crashes are the two most common crash types in terms of crash risk and severity. These crashes were more prevalent on high-speed roads, undivided roads, roads with no sidewalks and two-lane rural roads. Moreover, FS-related crashes were more likely to occur at night without street lighting, leading to more severe injuries. }
}
@article{Yan20111751,
title = {Motor vehicle–bicycle crashes in Beijing: Irregular maneuvers, crash patterns, and injury severity },
journal = {Accident Analysis & Prevention },
volume = {43},
number = {5},
pages = {1751 - 1758},
year = {2011},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2011.04.006},
url = {http://www.sciencedirect.com/science/article/pii/S000145751100087X},
author = {Xinping Yan and Ming Ma and Helai Huang and Mohamed Abdel-Aty and Chaozhong Wu},
keywords = {Motor vehicle–bicycle crash},
keywords = {Irregular maneuver},
keywords = {Crash pattern},
keywords = {Injury severity},
keywords = {Logit model },
abstract = {This research presents a comprehensive analysis of motor vehicle–bicycle crashes using 4 years of reported crash data (2004–2007) in Beijing. The interrelationship of irregular maneuvers, crash patterns and bicyclist injury severity are investigated by controlling for a variety of risk factors related to bicyclist demographics, roadway geometric design, road environment, etc. Results show that different irregular maneuvers are correlated with a number of risk factors at different roadway locations such as the bicyclist age and gender, weather and traffic condition. Furthermore, angle collisions are the leading pattern of motor vehicle–bicycle crashes, and different irregular maneuvers may lead to some specific crash patterns such as head-on or rear-end crashes. Orthokinetic scrape is more likely to result in running over bicyclists, which may lead to more severe injury. Moreover, bicyclist injury severity level could be elevated by specific crash patterns and risk factors including head-on and angle collisions, occurrence of running over bicyclists, night without streetlight, roads without median/division, higher speed limit, heavy vehicle involvement and older bicyclists. This study suggests installation of median, division between roadway and bikeway, and improvement of illumination on road segments. Reduced speed limit is also recommended at roadway locations with high bicycle traffic volume. Furthermore, it may be necessary to develop safety campaigns aimed at male, teenage and older bicyclists. }
}
@article{Haleem2010347,
title = {Examining traffic crash injury severity at unsignalized intersections },
journal = {Journal of Safety Research },
volume = {41},
number = {4},
pages = {347 - 357},
year = {2010},
note = {},
issn = {0022-4375},
doi = {http://dx.doi.org/10.1016/j.jsr.2010.04.006},
url = {http://www.sciencedirect.com/science/article/pii/S002243751000068X},
author = {Kirolos Haleem and Mohamed Abdel-Aty},
keywords = {Ordered probit},
keywords = {Binary probit},
keywords = {Nested logit},
keywords = {3-Legged unsignalized intersection},
keywords = {4-Legged unsignalized intersection},
keywords = {Injury severity},
keywords = {Crash severity },
abstract = {Introduction This study presents multiple approaches to the analysis of crash injury severity at three- and four-legged unsignalized intersections in the state of Florida from 2003 until 2006. An extensive data collection process was conducted for this study. Method The dataset used in the analysis included 2,043 unsignalized intersections in six counties in the state of Florida. For the scope of this study, there were three approaches explored. The first approach dealt with the five injury levels, and an ordered probit model was fitted. The second approach was an aggregated one, and dealt with only the severe versus non-severe crash levels, and a binary probit model was used. The third approach dealt with fitting a nested logit model. Results from the three fitted approaches were shown and discussed, and a comparison between the three approaches was shown. Results Several important factors affecting crash severity at unsignalized intersections were identified. These include the traffic volume on the major approach, and the number of through lanes on the minor approach (surrogate measure for traffic volume), and among the geometric factors, the upstream and downstream distance to the nearest signalized intersection, left and right shoulder width, number of left turn movements on the minor approach, and number of right and left turn lanes on the major approach. As for driver factors, young and very young at-fault drivers were associated with the least fatal probability compared to other age groups. Impact on industry The analysis identified some countermeasures to reduce injury severity at unsignalized intersections. The spatial covariates showed the importance of including safety awareness campaigns for speeding enforcement. Also, having a 90-degree intersection design is the most appropriate safety design for reducing severity. Moreover, the assurance of marking stop lines at unsignalized intersections is very essential. }
}
@article{Pande2009145,
title = {Market basket analysis of crash data from large jurisdictions and its potential as a decision support tool },
journal = {Safety Science },
volume = {47},
number = {1},
pages = {145 - 154},
year = {2009},
note = {},
issn = {0925-7535},
doi = {http://dx.doi.org/10.1016/j.ssci.2007.12.001},
url = {http://www.sciencedirect.com/science/article/pii/S0925753507001877},
author = {Anurag Pande and Mohamed Abdel-Aty},
keywords = {Association rules},
keywords = {Crash characteristics},
keywords = {Data mining},
keywords = {Traffic safety },
abstract = {Data mining applications are becoming increasingly popular for many applications across a set of very divergent fields. Analysis of crash data is no exception. There are many data mining methodologies that have been applied to crash data in the recent past. However, one particular application conspicuously missing from the traffic safety literature until recently is association analysis or market basket analysis. The methodology is used by retailers all over the world to determine which items are purchased together. In this study, crashes are analyzed as supermarket transactions to detect interdependence among crash characteristics. The results from the analysis include simple rules that indicate which crash characteristics are associated with each other. The application is demonstrated using non-intersection crash data from the state of Florida for the year 2004. In the proposed methodology no variable needs to be assigned as dependent variable. Hence, it is useful in identifying previously unknown patterns in the data obtained from large jurisdictions (such as the State of Florida) as opposed to the data from a single roadway or intersection. Based on the association rules discovered from the analysis, it was concluded that there is a significant correlation between lack of illumination and high severity of crashes. Furthermore, it was found that under rainy conditions straight sections with vertical curves are particularly crash prone. Results are consistent with the understanding of crash characteristics and point to the potential of this methodology for the analysis of crash data collected by the state and federal agencies. The potential of this technique may be realized in the form of a decision support tool for the traffic safety administrators. }
}
@article{AbdelAty2011461,
title = {Analyzing angle crashes at unsignalized intersections using machine learning techniques },
journal = {Accident Analysis & Prevention },
volume = {43},
number = {1},
pages = {461 - 470},
year = {2011},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2010.10.002},
url = {http://www.sciencedirect.com/science/article/pii/S0001457510002812},
author = {Mohamed Abdel-Aty and Kirolos Haleem},
keywords = {Data mining},
keywords = {Machine learning},
keywords = {Multivariate adaptive regression splines},
keywords = {\{MARS\}},
keywords = {Angle crash},
keywords = {Random forest},
keywords = {Unsignalized intersections},
keywords = {Crash prediction },
abstract = {A recently developed machine learning technique, multivariate adaptive regression splines (MARS), is introduced in this study to predict vehicles’ angle crashes. \{MARS\} has a promising prediction power, and does not suffer from interpretation complexity. Negative Binomial (NB) and \{MARS\} models were fitted and compared using extensive data collected on unsignalized intersections in Florida. Two models were estimated for angle crash frequency at 3- and 4-legged unsignalized intersections. Treating crash frequency as a continuous response variable for fitting a \{MARS\} model was also examined by considering the natural logarithm of the crash frequency. Finally, combining \{MARS\} with another machine learning technique (random forest) was explored and discussed. The fitted \{NB\} angle crash models showed several significant factors that contribute to angle crash occurrence at unsignalized intersections such as, traffic volume on the major road, the upstream distance to the nearest signalized intersection, the distance between successive unsignalized intersections, median type on the major approach, percentage of trucks on the major approach, size of the intersection and the geographic location within the state. Based on the mean square prediction error (MSPE) assessment criterion, \{MARS\} outperformed the corresponding \{NB\} models. Also, using \{MARS\} for predicting continuous response variables yielded more favorable results than predicting discrete response variables. The generated \{MARS\} models showed the most promising results after screening the covariates using random forest. Based on the results of this study, \{MARS\} is recommended as an efficient technique for predicting crashes at unsignalized intersections (angle crashes in this study). }
}
@article{Yan2008274,
title = {Validating a driving simulator using surrogate safety measures },
journal = {Accident Analysis & Prevention },
volume = {40},
number = {1},
pages = {274 - 288},
year = {2008},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2007.06.007},
url = {http://www.sciencedirect.com/science/article/pii/S0001457507001054},
author = {Xuedong Yan and Mohamed Abdel-Aty and Essam Radwan and Xuesong Wang and Praveen Chilakapati},
keywords = {Driving simulator},
keywords = {Signalized intersections},
keywords = {Geo-specific database modeling},
keywords = {Speed validation},
keywords = {Safety validation},
keywords = {Rear-end crashes },
abstract = {Traffic crash statistics and previous research have shown an increased risk of traffic crashes at signalized intersections. How to diagnose safety problems and develop effective countermeasures to reduce crash rate at intersections is a key task for traffic engineers and researchers. This study aims at investigating whether the driving simulator can be used as a valid tool to assess traffic safety at signalized intersections. In support of the research objective, this simulator validity study was conducted from two perspectives, a traffic parameter (speed) and a safety parameter (crash history). A signalized intersection with as many important features (including roadway geometries, traffic control devices, intersection surroundings, and buildings) was replicated into a high-fidelity driving simulator. A driving simulator experiment with eight scenarios at the intersection were conducted to determine if the subjects’ speed behavior and traffic risk patterns in the driving simulator were similar to what were found at the real intersection. The experiment results showed that speed data observed from the field and in the simulator experiment both follow normal distributions and have equal means for each intersection approach, which validated the driving simulator in absolute terms. Furthermore, this study used an innovative approach of using surrogate safety measures from the simulator to contrast with the crash analysis for the field data. The simulator experiment results indicated that compared to the right-turn lane with the low rear-end crash history record (2 crashes), subjects showed a series of more risky behaviors at the right-turn lane with the high rear-end crash history record (16 crashes), including higher deceleration rate (1.80 ± 1.20 m/s2 versus 0.80 ± 0.65 m/s2), higher non-stop right-turn rate on red (81.67% versus 57.63%), higher right-turn speed as stop line (18.38 ± 8.90 km/h versus 14.68 ± 6.04 km/h), shorter following distance (30.19 ± 13.43 m versus 35.58 ± 13.41 m), and higher rear-end probability (9/59 = 0.153 versus 2/60 = 0.033). Therefore, the relative validity of driving simulator was well established for the traffic safety studies at signalized intersections. }
}
@article{Harb20071026,
title = {Light truck vehicles (LTVs) contribution to rear-end collisions },
journal = {Accident Analysis & Prevention },
volume = {39},
number = {5},
pages = {1026 - 1036},
year = {2007},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2007.01.007},
url = {http://www.sciencedirect.com/science/article/pii/S000145750700019X},
author = {Rami Harb and Essam Radwan and Xuedong Yan and Mohamed Abdel-Aty},
keywords = {Light truck vehicle (LTV)},
keywords = {Rear-end collision},
keywords = {Horizontal visibility blockage},
keywords = {Driving simulator},
keywords = {Brake response time},
keywords = {Deceleration rate },
abstract = {Light truck vehicles (LTVs), comprising light-duty trucks, vans, and sport-utility vehicles (SUVs) drive higher and wider than passenger cars which could affect the visibility for the following passenger car driver. This paper investigates the contribution of \{LTVs\} to rear-end collisions resulting from horizontal visibility blockage using the University of Central Florida sophisticated reconfigurable driving simulator. Indeed, a sudden stop of a leading LTV, in the shadow of the blindness of the succeeding passenger car driver, may deprive the latter of a sufficient response time, which may lead to high probability of a rear-end collision. To investigate this issue, two scenarios were developed in the \{UCF\} driving simulator. The first scenario serves as a base scenario where the simulator car follows a passenger car, and the second scenario serves as a test scenario, where the simulator car follows an LTV. The results obtained by comparing the scenarios showed that \{LTVs\} produce more rear-end collisions at unsignalized intersections due to horizontal visibility blockage and due to the resulting drivers’ behavior when driving behind an LTV. }
}
@article{Guo201084,
title = {Modeling signalized intersection safety with corridor-level spatial correlations },
journal = {Accident Analysis & Prevention },
volume = {42},
number = {1},
pages = {84 - 92},
year = {2010},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2009.07.005},
url = {http://www.sciencedirect.com/science/article/pii/S0001457509001705},
author = {Feng Guo and Xuesong Wang and Mohamed A. Abdel-Aty},
keywords = {Bayesian approach},
keywords = {Signalized intersection},
keywords = {Safety analysis},
keywords = {Corridor},
keywords = {Spatial model},
keywords = {Conditional autoregressive model },
abstract = {Intersections in close spatial proximity along a corridor should be considered as correlated due to interacted traffic flows as well as similar road design and environmental characteristics. It is critical to incorporate this spatial correlation for assessing the true safety impacts of risk factors. In this paper, several Bayesian models were developed to model the crash data from 170 signalized intersections in the state of Florida. The safety impacts of risk factors such as geometric design features, traffic control, and traffic flow characteristics were evaluated. The Poisson and Negative Binomial Bayesian models with non-informative priors were fitted but the focus is to incorporate spatial correlations among intersections. Two alternative models were proposed to capture this correlation: (1) a mixed effect model in which the corridor-level correlation is incorporated through a corridor-specific random effect and (2) a conditional autoregressive model in which the magnitude of correlations is determined by spatial distances among intersections. The models were compared using the Deviance Information Criterion. The results indicate that the Poisson spatial model provides the best model fitting. Analysis of the posterior distributions of model parameters indicated that the size of intersection, the traffic conditions by turning movement, and the coordination of signal phase have significant impacts on intersection safety. }
}
@article{Wang200876,
title = {Modeling left-turn crash occurrence at signalized intersections by conflicting patterns },
journal = {Accident Analysis & Prevention },
volume = {40},
number = {1},
pages = {76 - 88},
year = {2008},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2007.04.006},
url = {http://www.sciencedirect.com/science/article/pii/S0001457507000711},
author = {Xuesong Wang and Mohamed Abdel-Aty},
keywords = {Signalized intersection},
keywords = {Left-turn crashes},
keywords = {Conflicting patterns},
keywords = {Approach level model},
keywords = {Negative Binomial},
keywords = {Generalized Estimating Equations },
abstract = {In order to better understand the underlying crash mechanisms, left-turn crashes occurring at 197 four-legged signalized intersections over 6 years were classified into nine patterns based on vehicle maneuvers and then were assigned to intersection approaches. Crash frequency of each pattern was modeled at the approach level by mainly using Generalized Estimating Equations (GEE) with the Negative Binomial as the link function to account for the correlation among the crash data. \{GEE\} with a binomial logit link function was also applied for patterns with fewer crashes. The Cumulative Residuals test shows that, for correlated left-turn crashes, \{GEE\} models usually outperformed basic Negative Binomial models. The estimation results show that there are obvious differences in the factors that cause the occurrence of different left-turn collision patterns. For example, for each pattern, the traffic flows to which the colliding vehicles belong are identified to be significant. The width of the crossing distance (represented by the number of through lanes on the opposing approach of the left-turning traffic) is associated with more left-turn traffic colliding with opposing through traffic (Pattern 5), but with less left-turning traffic colliding with near-side crossing through traffic (Pattern 8). The safety effectiveness of the left-turning signal is not consistent for different crash patterns; “protected” phasing is correlated with fewer Pattern 5 crashes, but with more Pattern 8 crashes. The study indicates that in order to develop efficient countermeasures for left-turn crashes and improve safety at signalized intersections, left-turn crashes should be considered in different patterns. }
}
@article{AbdelAty2009777,
title = {Safety evaluation of multilane arterials in Florida },
journal = {Accident Analysis & Prevention },
volume = {41},
number = {4},
pages = {777 - 788},
year = {2009},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2009.03.015},
url = {http://www.sciencedirect.com/science/article/pii/S0001457509000657},
author = {Mohamed Abdel-Aty and Prem Chand Devarasetty and Anurag Pande},
keywords = {Resurfacing},
keywords = {Safety evaluation},
keywords = {Empirical Bayes},
keywords = {Safety performance function},
keywords = {Severe crashes},
keywords = {Multilane arterials },
abstract = {Resurfacing is one of the more common construction activities on highways. While its effect on riding quality on any type of roadway is obviously positive; its impact on safety as measured in terms of crashes is far from obvious. This study examines the safety effects of the resurfacing projects on multilane arterials with partially limited access. Empirical Bayes method, which is one of the most accepted approaches for conducting before–after evaluations, has been used to assess the safety effects of the resurfacing projects. Safety effects are estimated not only in terms of all crashes but also rear-end as well as severe crashes (crashes involving incapacitating and fatal injuries). The safety performance functions (SPFs) used in this study are negative binomial crash frequency estimation models that use the information on ADT, length of the segments, speed limit and number of lanes. These \{SPFs\} are segregated by crash groups (all, rear-end, and severe), length of the segments being evaluated, and land use (urban, suburban, and rural). The results of the analysis show that the resulting changes in safety following resurfacing projects vary widely. Evaluating additional improvements carried out with resurfacing activities showed that all (other than sidewalk improvements for total crashes) of them consistently led to improvements in safety of multilane arterial sections. It leads to the inference that it may be a good idea to take up additional improvements if it is cost effective to do them along with resurfacing. It was also found that the addition of turning lanes (left and/or right) and paving shoulders were two improvements associated with a project's relative performance in terms of reduction in rear-end crashes. }
}
@article{Das20111156,
title = {A combined frequency–severity approach for the analysis of rear-end crashes on urban arterials },
journal = {Safety Science },
volume = {49},
number = {8–9},
pages = {1156 - 1163},
year = {2011},
note = {},
issn = {0925-7535},
doi = {http://dx.doi.org/10.1016/j.ssci.2011.03.007},
url = {http://www.sciencedirect.com/science/article/pii/S0925753511000774},
author = {Abhishek Das and Mohamed A. Abdel-Aty},
keywords = {Arterial safety},
keywords = {Genetic Programming},
keywords = {Injury severity},
keywords = {Crash frequency},
keywords = {Sensitivity analysis },
abstract = {Analysis of both the crash count and the severity of injury are required to provide the complete picture of the safety situation of any given roadway. The randomness of crashes, the one-way dependency of injury on crash occurrence and the difference in response types have typically led researchers into developing independent statistical models for crash count and severity classification. The Genetic Programming (GP) methodology adopts the concepts of evolutionary biology such as crossover and mutation in effectively giving a common heuristic approach to model the development for the two different modeling objectives. The chosen \{GP\} models have the highest hit rate for rear-end crash classification problem and the least error for function fitting (regression) problems. Higher Average Daily Traffic (ADT) is more likely to result in more crashes. Absence of on-street parking may result in diminished severity of injuries resulting from crashes as they may provide “soft” crash barrier in contrast to fixed road side objects. Graphical presentation of the frequency of crashes with varying input variables shed new light on the results and its interpretation. Higher friction coefficient of roadways result in reduced frequency of crashes during the morning peak hours, with the trend being reversed during the afternoon peak hours. Crash counts have been observed to be at a maximum at a surface width of 30 ft. Sensitivity analysis results reflect that \{ADT\} is responsible for the largest variation in crash counts on urban arterials. }
}
@article{Haleem2010654,
title = {Using a reliability process to reduce uncertainty in predicting crashes at unsignalized intersections },
journal = {Accident Analysis & Prevention },
volume = {42},
number = {2},
pages = {654 - 666},
year = {2010},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2009.10.012},
url = {http://www.sciencedirect.com/science/article/pii/S0001457509002760},
author = {Kirolos Haleem and Mohamed Abdel-Aty and Kevin Mackie},
keywords = {Negative binomial model},
keywords = {Reliability},
keywords = {Bayesian updating},
keywords = {3-Legged unsignalized intersection},
keywords = {4-Legged unsignalized intersection},
keywords = {Crash prediction },
abstract = {The negative binomial (NB) model has been used extensively by traffic safety analysts as a crash prediction model, because it can accommodate the over-dispersion criterion usually exhibited in crash count data. However, the \{NB\} model is still a probabilistic model that may benefit from updating the parameters of the covariates to better predict crash frequencies at intersections. The objective of this paper is to examine the effect of updating the parameters of the covariates in the fitted \{NB\} model using a Bayesian updating reliability method to more accurately predict crash frequencies at 3-legged and 4-legged unsignalized intersections. For this purpose, data from 433 unsignalized intersections in Orange County, Florida were collected and used in the analysis. Four Bayesian-structure models were examined: (1) a non-informative prior with a log-gamma likelihood function, (2) a non-informative prior with an \{NB\} likelihood function, (3) an informative prior with an \{NB\} likelihood function, and (4) an informative prior with a log-gamma likelihood function. Standard measures of model effectiveness, such as the Akaike information criterion (AIC), mean absolute deviance (MAD), mean square prediction error (MSPE) and overall prediction accuracy, were used to compare the \{NB\} and Bayesian model predictions. Considering only the best estimates of the model parameters (ignoring uncertainty), both the \{NB\} and Bayesian models yielded favorable results. However, when considering the standard errors for the fitted parameters as a surrogate measure for measuring uncertainty, the Bayesian methods yielded more promising results. The full Bayesian updating framework using the log-gamma likelihood function for updating parameter estimates of the \{NB\} probabilistic models resulted in the least standard error values. }
}
@article{Wang20061137,
title = {Temporal and spatial analyses of rear-end crashes at signalized intersections },
journal = {Accident Analysis & Prevention },
volume = {38},
number = {6},
pages = {1137 - 1150},
year = {2006},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2006.04.022},
url = {http://www.sciencedirect.com/science/article/pii/S0001457506000789},
author = {Xuesong Wang and Mohamed Abdel-Aty},
keywords = {Rear-end crashes},
keywords = {Signalized intersections},
keywords = {Temporal correlation},
keywords = {Spatial correlation},
keywords = {Negative binomial},
keywords = {Generalized estimating equations },
abstract = {In this study, the generalized estimating equations with the negative binomial link function were used to model rear-end crash frequencies at signalized intersections to account for the temporal or spatial correlation among the data. The longitudinal data for 208 signalized intersections over 3 years and the spatially correlated data for 476 signalized intersections which are located along different corridors were collected in the state of Florida. The modeling results showed that there are high correlations between the longitudinal or spatially correlated rear-end crashes. Some intersection related variables are identified as significantly influencing rear-end crash occurrences at signalized intersections. Intersections with heavy traffic on the major and minor roadways, having more right and left-turn lanes on the major roadway, having a large number of phases per cycle (indicated by the left-turn protection on the minor roadway), with high speed limits on the major roadway, and in high population areas are correlated with high rear-end crash frequencies. On the other hand, intersections with three legs, having channelized or exclusive right-turn lanes on the minor roadway, with protected left-turning on the major roadway, with medians on the minor roadway, and having longer signal spacing have a lower frequency of rear-end crashes. }
}
@article{Lee20081703,
title = {Presence of passengers: Does it increase or reduce driver's crash potential? },
journal = {Accident Analysis & Prevention },
volume = {40},
number = {5},
pages = {1703 - 1712},
year = {2008},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2008.06.006},
url = {http://www.sciencedirect.com/science/article/pii/S0001457508000997},
author = {Chris Lee and Mohamed Abdel-Aty},
keywords = {Passenger},
keywords = {Driver},
keywords = {Freeway crash},
keywords = {Bivariate probit},
keywords = {Binary logit },
abstract = {This study examines the impact of passengers on the driver's crash potential on freeways. To estimate the impact, a set of bivariate probit models were developed using the 5-year (1999–2003) crash records on a 36.3-mile stretch of Interstate-4 freeway (I-4) in Orlando, Florida. Bivariate probit models identify the correlation between potentially inter-related choices of three passenger characteristics and three crash characteristics. The analysis using bivariate probit models showed that there exist strong correlations between passenger and crash characteristics. It was found that drivers generally display safer driving behavior when they are accompanied by passengers, and more passengers reduce driver's crash potential. It was also found that younger driver's crash potential increases with the presence of a younger passenger only. In addition, the analysis of crash type using traffic flow parameters at the time of crashes showed that young drivers with only younger passengers are more likely to be involved in single-vehicle crashes in high-speed and low-volume conditions. The findings in this study provide insight into how the presence of passengers has an impact on driver behavior and traffic safety in various conditions. }
}
@article{AbdelAty2007355,
title = {Detecting periodic patterns of arrival delay },
journal = {Journal of Air Transport Management },
volume = {13},
number = {6},
pages = {355 - 361},
year = {2007},
note = {},
issn = {0969-6997},
doi = {http://dx.doi.org/10.1016/j.jairtraman.2007.06.002},
url = {http://www.sciencedirect.com/science/article/pii/S0969699707000646},
author = {Mohamed Abdel-Aty and Chris Lee and Yuqiong Bai and Xin Li and Martin Michalak},
keywords = {Flight delays},
keywords = {Periodicity},
keywords = {Frequency analysis},
keywords = {Airport operations },
abstract = {This study identifies the periodic patterns of arrival delay for non-stop domestic flights at the Orlando International Airport during 2002–2003. Cyclic variations in air travel demand and weather at the airport were observed and their consequent effects on flight delay were investigated. This study detected the frequencies of any regularly repeating delay patterns and then identified the factors associated with the detected frequencies of delay. These sequential tasks called the “two-stage approach” were performed using a mathematical frequency analysis and statistical analysis techniques. The results of the frequency analysis showed that arrival delay displayed daily, weekly and seasonal patterns of variation. The results of the statistical analysis showed that time of day, day of week, season, flight distance, precipitation at \{MCO\} and scheduled time intervals between successive flights were significantly correlated with arrival delay. }
}
@article{AbdelAty2007571,
title = {Geo-spatial and log-linear analysis of pedestrian and bicyclist crashes involving school-aged children },
journal = {Journal of Safety Research },
volume = {38},
number = {5},
pages = {571 - 579},
year = {2007},
note = {},
issn = {0022-4375},
doi = {http://dx.doi.org/10.1016/j.jsr.2007.04.006},
url = {http://www.sciencedirect.com/science/article/pii/S0022437507001053},
author = {Mohamed Abdel-Aty and Sai Srinivas Chundi and Chris Lee},
keywords = {School children},
keywords = {Pedestrian crashes},
keywords = {Bicycle crashes},
keywords = {Geographic Information Systems},
keywords = {Log-linear model },
abstract = {Problem There is a growing concern with the safety of school-aged children. This study identifies the locations of pedestrian/bicyclist crashes involving school-aged children and examines the conditions when these crashes are more likely to occur. Method The 5-year records of crashes in Orange County, Florida where school-aged children were involved were used. The spatial distribution of these crashes was investigated using the Geographic Information Systems (GIS) and the likelihoods of crash occurrence under different conditions were estimated using log-linear models. Results A majority of school-aged children crashes occurred in the areas near schools. Although elementary school children were generally very involved, middle and high school children were more involved in crashes, particularly on high-speed multi-lane roadways. Driver's age, gender, and alcohol use, pedestrian's/bicyclist's age, number of lanes, median type, speed limits, and speed ratio were also found to be correlated with the frequency of crashes. Discussion The result confirms that school-aged children are exposed to high crash risk near schools. High crash involvement of middle and high school children reflects that middle and high schools tend to be located near multi-lane high-speed roads. Impact on Industry The pedestrian's/bicyclist's demographic factors and geometric characteristics of the roads adjacent to schools associated with school children's crash involvement are of interest to school districts. }
}
@article{AbdelAty2007113,
title = {Considering various \{ALINEA\} ramp metering strategies for crash risk mitigation on freeways under congested regime },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {15},
number = {2},
pages = {113 - 134},
year = {2007},
note = {},
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/j.trc.2007.02.003},
url = {http://www.sciencedirect.com/science/article/pii/S0968090X07000058},
author = {Mohamed Abdel-Aty and Albinder Dhindsa and Vikash Gayah},
keywords = {Crash risk},
keywords = {Freeway safety},
keywords = {Ramp metering},
keywords = {Micro-simulation },
abstract = {This study evaluates the expected benefits of using the \{ALINEA\} ramp metering algorithm as a method for real-time safety improvement on an urban freeway. The objective of this research is to use ramp metering to produce a significant decrease in the risk of crashes on the freeway while avoiding any significant adverse effects on operation. This is achieved by simulating the freeway during the congested period in micro-simulation and testing various ramp metering configurations to determine which provides the best results. Statistical measures developed for the same stretch of freeway using loop detector data are used to quantify the risk of crashes as well as the benefits in each of the alternative strategies. The study concludes that there are significant benefits in metering multiple ramps when the feedback ramp metering algorithm is implemented at multiple locations. It was found that increasing the number of metered on-ramps produces increasing safety benefits. Also, a shorter cycle length for each of the meters and a higher critical occupancy value leads to better results. }
}
@article{Yan2005983,
title = {Characteristics of rear-end accidents at signalized intersections using multiple logistic regression model },
journal = {Accident Analysis & Prevention },
volume = {37},
number = {6},
pages = {983 - 995},
year = {2005},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2005.05.001},
url = {http://www.sciencedirect.com/science/article/pii/S0001457505000801},
author = {Xuedong Yan and Essam Radwan and Mohamed Abdel-Aty},
keywords = {Rear-end accidents},
keywords = {Signalized intersections},
keywords = {Quasi-induced exposure},
keywords = {Multiple logistic regression},
keywords = {Striking role},
keywords = {Struck role },
abstract = {Multi-vehicle rear-end accidents constitute a substantial portion of the accidents occurring at signalized intersections. To examine the accident characteristics, this study utilized the 2001 Florida traffic accident data to investigate the accident propensity for different vehicle roles (striking or struck) that are involved in the accidents and identify the significant risk factors related to the traffic environment, the driver characteristics, and the vehicle types. The Quasi-induced exposure concept and the multiple logistic regression technique are used to perform this analysis. The results showed that seven road environment factors (number of lanes, divided/undivided highway, accident time, road surface condition, highway character, urban/rural, and speed limit), five factors related to striking role (vehicle type, driver age, alcohol/drug use, driver residence, and gender), and four factors related to struck role (vehicle type, driver age, driver residence, and gender) are significantly associated with the risk of rear-end accidents. Furthermore, the logistic regression technique confirmed several significant interaction effects between those risk factors. }
}
@article{AbdelAty2003597,
title = {Analysis of driver injury severity levels at multiple locations using ordered probit models },
journal = {Journal of Safety Research },
volume = {34},
number = {5},
pages = {597 - 603},
year = {2003},
note = {},
issn = {0022-4375},
doi = {http://dx.doi.org/10.1016/j.jsr.2003.05.009},
url = {http://www.sciencedirect.com/science/article/pii/S0022437503000811},
author = {Mohamed Abdel-Aty},
keywords = {Injury severity},
keywords = {Signalized intersections},
keywords = {Toll plazas},
keywords = {Roadway sections},
keywords = {Ordered probit },
abstract = {Problem: The occurrence and outcome of traffic crashes have long been recognized as complex events involving interactions between many factors, including the roadway, driver, traffic characteristics, and the environment. This study is concerned with the outcome of the crash. Method: Driver injury severity levels are analyzed using the ordered probit modeling methodology. Models were developed for roadway sections, signalized intersections, and toll plazas in Central Florida. All models showed the significance of driver's age, gender, seat belt use, point of impact, speed, and vehicle type on the injury severity level. Other variables were found significant only in specific cases. Results: A driver's violation was significant in the case of signalized intersections. Alcohol, lighting conditions, and the existence of a horizontal curve affected the likelihood of injuries in the roadway sections' model. A variable specific to toll plazas, vehicles equipped with Electronic Toll Collection (ETC), had a positive effect on the probability of higher injury severity at toll plazas. Other variables that entered into some of the models were weather condition, area type, and some interaction factors. This study illustrates the similarities and the differences in the factors that affect injury severity between different locations. }
}
@article{AbdelAty2004457,
title = {Analysis and prediction of traffic fatalities resulting from angle collisions including the effect of vehicles’ configuration and compatibility },
journal = {Accident Analysis & Prevention },
volume = {36},
number = {3},
pages = {457 - 469},
year = {2004},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/S0001-4575(03)00041-1},
url = {http://www.sciencedirect.com/science/article/pii/S0001457503000411},
author = {Mohamed Abdel-Aty and Hassan Abdelwahab},
keywords = {Light truck vehicle},
keywords = {Time series analysis},
keywords = {Angle collisions},
keywords = {Traffic fatalities},
keywords = {Collision},
keywords = {Configuration},
keywords = {Traffic composition },
abstract = {Although the rapid growth in light truck vehicle (LTV) sales, including minivans, sports utility vehicles (SUVs), and light-duty trucks, has not been associated with an overall increase in collisions or traffic deaths in the US, there is a need for a research program to determine whether particular types of collisions have become more frequent or injurious because of the increase in the percent of \{LTVs\} in traffic. This paper presents an analysis of the effect of the increasing number of \{LTV\} registrations on fatal angle collision trends in the US. The analysis investigates the number of annual fatalities that result from angle collisions as well as collision configuration (car–car, car–LTV, LTV–car, and LTV–LTV). The analysis uses the Fatality Analysis Reporting System (FARS) crash databases covering the period 1975–2000. Results showed that death rates differ based on the collision configuration. Time series modeling results showed that fatalities in angle collisions will increase in the next 10 years, and that they are affected by the expected increase in the percentage of \{LTVs\} in traffic. Forecast showed that the total number of annual deaths is expected to reach 6300 deaths by the year 2010 (an increase of 12% over 2000). Analysis into the configuration of the collision indicated the seriousness of angle collisions involving an \{LTV\} striking a common passenger car (LTV–car). A time series model illustrated the significance of time lag and percent of \{LTVs\} in traffic on the increase of this type of fatal collisions. Forecasts from the time series model indicated a 32% increase in deaths due to this type of collisions in the next 10 years. }
}
@article{AbdelAty2005417,
title = {Exploring the overall and specific crash severity levels at signalized intersections },
journal = {Accident Analysis & Prevention },
volume = {37},
number = {3},
pages = {417 - 425},
year = {2005},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2004.11.002},
url = {http://www.sciencedirect.com/science/article/pii/S0001457504001186},
author = {Mohamed Abdel-Aty and Joanne Keller},
keywords = {Signalized intersections},
keywords = {Crash severity},
keywords = {Ordered probit models},
keywords = {Tree-based regression},
keywords = {Traffic safety data },
abstract = {Many studies have shown that intersections are among the most dangerous locations of a roadway network. Therefore, there is a need to understand the factors that contribute to injuries at such locations. This paper addresses the different factors that affect crash injury severity at signalized intersections. It also looks into the quality and completeness of the crash data and the effect that incomplete data has on the final results. Data from multiple sources have been cross-checked to ensure the completeness of all crashes including minor crashes that are usually unreported or not coded into crash databases. The ordered probit modeling technique has been adopted in this study to account for the fact that injury levels are naturally ordered variables. The tree-based regression methodology has also been adopted in this study to explore the factors that affect each severity level. The probit model results showed that a combination of crash-specific information and intersection characteristics result in the highest prediction rate of injury level. More specifically, having a divided minor roadway or a higher speed limit on the minor roadway decreased the level of injury while crashes involving a pedestrian/bicyclist and left turn crashes had the highest probability of a more severe crash. Several regression tree models showed a difference in the significant factors that affect the different severity types. Completing the data with minor non injury crashes improved the modeling results and depicted differences when modeling the no injury crashes. }
}
@article{AbdelAty2001265,
title = {Using ordered probit modeling to study the effect of \{ATIS\} on transit ridership },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {9},
number = {4},
pages = {265 - 277},
year = {2001},
note = {},
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/S0968-090X(00)00037-1},
url = {http://www.sciencedirect.com/science/article/pii/S0968090X00000371},
author = {Mohamed A. Abdel-Aty},
keywords = {Transit information},
keywords = {Transit attributes},
keywords = {Customized surveys},
keywords = {Stated preference},
keywords = {Ordered probit models },
abstract = {A computer-aided telephone interview was conducted in two metropolitan areas in northern California. The survey included an innovative stated preference design to collect data that address the potential of advanced transit information systems. The study’s main objectives are to investigate whether advanced transit information would increase the acceptance of transit, and to determine the types and levels of information that are desired by commuters. The survey included a customized procedure that presents realistic choice sets, including the respondent’s preferred information items and realistic travel times. The ordered probit modeling technique was used. The results indicated a promising potential of advanced transit information in increasing the acceptance of transit as a commute mode. It also showed that the frequency of service, number of transfers, seat availability, walking time to the transit stop and fare information are among the significant information types that commuters desire. Commute time by transit, income, education, and whether the commuter is currently carpooling, were among the factors that contribute to the likelihood of using transit given information was provided. }
}
@article{AbdelAty2000633,
title = {Modeling traffic accident occurrence and involvement },
journal = {Accident Analysis & Prevention },
volume = {32},
number = {5},
pages = {633 - 642},
year = {2000},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/S0001-4575(99)00094-9},
url = {http://www.sciencedirect.com/science/article/pii/S0001457599000949},
author = {Mohamed A. Abdel-Aty and A.Essam Radwan},
keywords = {Accident occurrence},
keywords = {Accident involvement},
keywords = {Negative Binomial models},
keywords = {Roadway geometric characteristics},
keywords = {Driver characteristics},
keywords = {Traffic safety },
abstract = {The Negative Binomial modeling technique was used to model the frequency of accident occurrence and involvement. Accident data over a period of 3 years, accounting for 1606 accidents on a principal arterial in Central Florida, were used to estimate the model. The model illustrated the significance of the Annual Average Daily Traffic (AADT), degree of horizontal curvature, lane, shoulder and median widths, urban/rural, and the section’s length, on the frequency of accident occurrence. Several Negative Binomial models of the frequency of accident involvement were also developed to account for the demographic characteristics of the driver (age and gender). The results showed that heavy traffic volume, speeding, narrow lane width, larger number of lanes, urban roadway sections, narrow shoulder width and reduced median width increase the likelihood for accident involvement. Subsequent elasticity computations identified the relative importance of the variables included in the models. Female drivers experience more accidents than male drivers in heavy traffic volume, reduced median width, narrow lane width, and larger number of lanes. Male drivers have greater tendency to be involved in traffic accidents while speeding. The models also indicated that young and older drivers experience more accidents than middle aged drivers in heavy traffic volume, and reduced shoulder and median widths. Younger drivers have a greater tendency of being involved in accidents on roadway curves and while speeding. }
}
@article{AbdelAty2000473,
title = {Exploring the relationship between alcohol and the driver characteristics in motor vehicle accidents },
journal = {Accident Analysis & Prevention },
volume = {32},
number = {4},
pages = {473 - 482},
year = {2000},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/S0001-4575(99)00062-7},
url = {http://www.sciencedirect.com/science/article/pii/S0001457599000627},
author = {Mohamed A. Abdel-Aty and Hassan T. Abdelwahab},
keywords = {Driver characteristics},
keywords = {Alcohol},
keywords = {Accidents},
keywords = {Conditional probability},
keywords = {Log-linear models },
abstract = {This study examines the differences in alcohol-related accident involvement among different driver groups in the state of Florida. The driver characteristics considered in this study are: age, gender, race, and residency of the driver of a motor vehicle involved in an accident while under the influence of alcohol, drugs, or alcohol and drugs. The main objective of this study is to test whether there are associations between the different driver characteristics and alcohol involvement in traffic accidents, and to identify the high-risk group within each driver factor. This would improve our understanding of the relationship between alcohol involvement, accidents, and the four aforementioned driver factors. It would also enable us to better design educational and awareness programs targeting specific groups in the population to reduce drinking and driving in the state. The relationship between alcohol-related accident involvement and the driver factors are investigated using general descriptive statistics, conditional probabilities and log-linear models. The results showed that the 25–34 age group experience the highest rate of alcohol/drug involvement in accidents. The rates decline with the increase in the age of the drivers. The results also indicated that there are significant relationships between the driver characteristics and alcohol/drug involvement in accidents. Male, white, and in-state drivers were also more involved in alcohol/drugs-related traffic accidents. }
}
@article{AbdelAty200597,
title = {Identifying crash propensity using specific traffic speed conditions },
journal = {Journal of Safety Research },
volume = {36},
number = {1},
pages = {97 - 108},
year = {2005},
note = {},
issn = {0022-4375},
doi = {http://dx.doi.org/10.1016/j.jsr.2004.11.002},
url = {http://www.sciencedirect.com/science/article/pii/S0022437504001197},
author = {Mohamed Abdel-Aty and Anurag Pande},
keywords = {Freeway crashes},
keywords = {Loop detectors},
keywords = {Crash prediction},
keywords = {Probabilistic Neural Networks},
keywords = {Traffic speed },
abstract = {Introduction: In spite of recent advances in traffic surveillance technology and ever-growing concern over traffic safety, there have been very few research efforts establishing links between real-time traffic flow parameters and crash occurrence. This study aims at identifying patterns in the freeway loop detector data that potentially precede traffic crashes. Method: The proposed solution essentially involves classification of traffic speed patterns emerging from the loop detector data. Historical crash and loop detector data from the Interstate-4 corridor in the Orlando metropolitan area were used for this study. Traffic speed data from sensors embedded in the pavement (i.e., loop detector stations) to measure characteristics of the traffic flow were collected for both crash and non-crash conditions. Bayesian classifier based methodology, probabilistic neural network (PNN), was then used to classify these data as belonging to either crashes or non-crashes. \{PNN\} is a neural network implementation of well-known Bayesian-Parzen classifier. With its superb mathematical credentials, the \{PNN\} trains much faster than multilayer feed forward networks. The inputs to final classification model, selected from various candidate models, were logarithms of the coefficient of variation in speed obtained from three stations, namely, station of the crash (i.e., station nearest to the crash location) and two stations immediately preceding it in the upstream direction (measured in 5 minute time slices of 10–15 minutes prior to the crash time). Results: The results showed that at least 70% of the crashes on the evaluation dataset could be identified using the classifiers developed in this paper. }
}
@article{AbdelAty2004447,
title = {Modeling rear-end collisions including the role of driver’s visibility and light truck vehicles using a nested logit structure },
journal = {Accident Analysis & Prevention },
volume = {36},
number = {3},
pages = {447 - 456},
year = {2004},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/S0001-4575(03)00040-X},
url = {http://www.sciencedirect.com/science/article/pii/S000145750300040X},
author = {Mohamed Abdel-Aty and Hassan Abdelwahab},
keywords = {Rear-end},
keywords = {Nested logit},
keywords = {Light truck vehicles},
keywords = {Vehicle compatibility},
keywords = {Crash configuration },
abstract = {This paper presents an analysis of the effect of the geometric incompatibility of light truck vehicles (LTV)—light-duty trucks, vans, and sport utility vehicles—on drivers’ visibility of other passenger cars involved in rear-end collisions. The geometric incompatibility arises from the fact that most \{LTVs\} ride higher and are wider than regular passenger cars. The objective of this paper is to explore the effect of the lead vehicle’s size on the rear-end crash configuration. Four rear-end crash configurations are defined based on the type of the two involved vehicles (lead and following vehicles). Nested logit models were calibrated to estimate the probabilities of the four rear-end crash configurations as a function of driver’s age, gender, vehicle type, vehicle maneuver, light conditions, driver’s visibility and speed. Results showed that driver’s visibility and inattention in the following (striker) vehicle have the largest effect on being involved in a rear-end collision of configuration CarTrk (a regular passenger car striking an LTV). Possibly, indicating a sight distance problem. A driver of a smaller car following an LTV, have a problem seeing the roadway beyond the LTV, and therefore would not be able to adjust his/her speed accordingly, increasing the probability of a rear-end collision. Also, the probability of a CarTrk rear-end crash increases in the case that the lead vehicle stops suddenly. }
}
@article{Pande2006936,
title = {Assessment of freeway traffic parameters leading to lane-change related collisions },
journal = {Accident Analysis & Prevention },
volume = {38},
number = {5},
pages = {936 - 948},
year = {2006},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2006.03.004},
url = {http://www.sciencedirect.com/science/article/pii/S0001457506000455},
author = {Anurag Pande and Mohamed Abdel-Aty},
keywords = {Lane-change crashes},
keywords = {Freeway crashes},
keywords = {Sideswipe collisions},
keywords = {Loop detector data},
keywords = {Data mining},
keywords = {Real-time traffic },
abstract = {This study aims at ‘predicting’ the occurrence of lane-change related freeway crashes using the traffic surveillance data collected from a pair of dual loop detectors. The approach adopted here involves developing classification models using the historical crash data and corresponding information on real-time traffic parameters obtained from loop detectors. The historical crash and loop detector data to calibrate the neural network models (corresponding to crash and non-crash cases to set up a binary classification problem) were collected from the Interstate-4 corridor in Orlando (FL) metropolitan area. Through a careful examination of crash data, it was concluded that all sideswipe collisions and the angle crashes that occur on the inner lanes (left most and center lanes) of the freeway may be attributed to lane-changing maneuvers. These crashes are referred to as lane-change related crashes in this study. The factors explored as independent variables include the parameters formulated to capture the overall measure of lane-changing and between-lane variations of speed, volume and occupancy at the station located upstream of crash locations. Classification tree based variable selection procedure showed that average speeds upstream and downstream of crash location, difference in occupancy on adjacent lanes and standard deviation of volume and speed downstream of the crash location were found to be significantly associated with the binary variable (crash versus non-crash). The classification models based on data mining approach achieved satisfactory classification accuracy over the validation dataset. The results indicate that these models may be applied for identifying real-time traffic conditions prone to lane-change related crashes. }
}
@article{Lee2005775,
title = {Comprehensive analysis of vehicle–pedestrian crashes at intersections in Florida },
journal = {Accident Analysis & Prevention },
volume = {37},
number = {4},
pages = {775 - 786},
year = {2005},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2005.03.019},
url = {http://www.sciencedirect.com/science/article/pii/S0001457505000564},
author = {Chris Lee and Mohamed Abdel-Aty},
keywords = {Pedestrian},
keywords = {Crash frequency},
keywords = {Injury severity},
keywords = {Exposure},
keywords = {Intersection },
abstract = {This study analyzes vehicle–pedestrian crashes at intersections in Florida over 4 years, 1999–2002. The study identifies the group of drivers and pedestrians, and traffic and environmental characteristics that are correlated with high pedestrian crashes using log-linear models. The study also estimates the likelihood of pedestrian injury severity when pedestrians are involved in crashes using an ordered probit model. To better reflect pedestrian crash risk, a logical measure of exposure is developed using the information on individual walking trips in the household travel survey. Lastly, the impact of average traffic volume on pedestrian crashes is examined. As a result of the analysis, it was found that pedestrian and driver demographic factors, and road geometric, traffic and environment conditions are closely related to the frequency and injury severity of pedestrian crashes. Higher average traffic volume at intersections increases the number of pedestrian crashes; however, the rate of increase is steeper at lower values of average traffic volume. Based on the findings in the analysis, some countermeasures are recommended to improve pedestrian safety. }
}
@article{Vaughn1999107,
title = {A framework for developing a daily activity and multimodal travel planner },
journal = {International Transactions in Operational Research },
volume = {6},
number = {1},
pages = {107 - 121},
year = {1999},
note = {},
issn = {0969-6016},
doi = {http://dx.doi.org/10.1016/S0969-6016(98)00052-5},
url = {http://www.sciencedirect.com/science/article/pii/S0969601698000525},
author = {Kenneth M. Vaughn and Mohamed A. Abdel-Aty and Ryuichi Kitamura},
keywords = {\{ATIS\}},
keywords = {Activity scheduling},
keywords = {Traveling salesman problem},
keywords = {Vehicle routing},
keywords = {Multimodal travel },
abstract = {There is a need to further explore ways to use Advanced Traveler Information Systems (ATIS) to encourage transit and ridesharing. One mechanism is to provide convenient travel itinerary information, not just for one trip, but for a day’s travel. The formulation should consider time constraints, activity needs, real transit service parameters and the actual street system. Basic algorithmic development is needed to spur the private sector interest in such a product by demonstrating its utility. The activity travel planner will aid its user in planning his daily itinerary by arranging the sequence of stops, suggesting and possibly selecting stop locations, providing transit route and schedule information, and suggesting travel routes. This paper develops a framework for solving the Travel Itinerary Planning Problem (TIPP) which is a variant of the Traveling Salesman Problem (TSP). Implementation of the solution algorithm would be used to develop and test a prototype for an activity and travel planner. }
}
@comment{{Subasish Das PAPERS}}
@article{das2015edge,
title = {Investigating Safety Impact of Edgelines on Narrow, Rural Two-Lane Highways by Empirical Bayes Method.},
author = {Subasish Das and Xiaoduan Sun and Fan Wang and Charles Leboeuf},
url = {http://trrjournalonline.trb.org/doi/abs/10.3141/2433-14},
booktitle = {Transportation Research Record},
number = {2433},
year = {2015}
}
@article{Das2015,
title = {Estimating likelihood of future crashes for crash-prone drivers },
journal = {Journal of Traffic and Transportation Engineering (English Edition) },
volume = {},
number = {0},
pages = { - },
year = {2015},
note = {},
issn = {2095-7564},
doi = {http://dx.doi.org/10.1016/j.jtte.2015.03.003},
url = {http://www.sciencedirect.com/science/article/pii/S2095756415000252},
author = {Subasish Das and Xiaoduan Sun and Fan Wang and Charles Leboeuf},
keywords = {Roadway safety},
keywords = {Crash-prone drivers},
keywords = {Crash risk},
keywords = {Logistic regression},
keywords = {Sensitivity },
abstract = {At-fault crash-prone drivers are usually considered as the high risk group for possible future incidents or crashes. In Louisiana, 34% of crashes are repeatedly committed by the at-fault crash-prone drivers who represent only 5% of the total licensed drivers in the state. This research has conducted an exploratory data analysis based on the driver faultiness and proneness. The objective of this study is to develop a crash prediction model to estimate the likelihood of future crashes for the at-fault drivers. The logistic regression method is used by employing eight years' traffic crash data (2004–2011) in Louisiana. Crash predictors such as the driver's crash involvement, crash and road characteristics, human factors, collision type, and environmental factors are considered in the model. The at-fault and not-at-fault status of the crashes are used as the response variable. The developed model has identified a few important variables, and is used to correctly classify at-fault crashes up to 62.40% with a specificity of 77.25%. This model can identify as many as 62.40% of the crash incidence of at-fault drivers in the upcoming year. Traffic agencies can use the model for monitoring the performance of an at-fault crash-prone drivers and making roadway improvements meant to reduce crash proneness. From the findings, it is recommended that crash-prone drivers should be targeted for special safety programs regularly through education and regulations. }
}
@article{das2015factor,
title = {Factor Association Using Multiple Correspondence Analysis in Vehicle-Pedestrian Crashes},
author = {Das, Subasish and Sun, Xiaoduan},
booktitle = {Transportation Research Record},
url = {http://www.sciencedirect.com/science/article/pii/S0191261513000180},
number = {},
year = {2015}
}
@article{sun2013four,
title = {Four-lane to five-lane urban roadway conversions for safety},
author = {Sun, Xiaoduan and Das, Subasish and Fruge, Nicholas and Bertinot, Ronald L and Magri, Daniel},
journal = {Journal of Transportation Safety \& Security},
volume = {5},
number = {2},
pages = {106--117},
year = {2013},
url = {http://www.tandfonline.com/eprint/aWcxwhVCv57sBUpWzydI/full},
publisher = {Taylor \& Francis}
}
@inproceedings{das2014investigating,
title = {Investigating the Pattern of Traffic Crashes under Rainy Weather by Association Rules in Data Mining 2},
author = {Das, Subasish and Sun, Xiaoduan},
booktitle = {Transportation Research Board 93rd Annual Meeting},
url = {http://trid.trb.org/view.aspx?id=1288303},
number = {14-1540},
year = {2014}
}
@inproceedings{das2015zero,
title = {Zero-Inflated Models for Different Severity Types in Rural Two-Lane Crashes},
author = {Das, Subasish and Sun, Xiaoduan},
booktitle = {Transportation Research Board 94th Annual Meeting},
url = {http://trid.trb.org/view.aspx?id=1288303},
number = {15-2539},
year = {2015}
}
@inproceedings{das2014exploring,
title = {Exploring Clusters of Contributing Factors for Single Vehicle Fatal Crashes through Multiple Correspondence Analysis 2},
author = {Das, Subasish and Sun, Xiaoduan},
booktitle = {Transportation Research Board 93rd Annual Meeting},
url = {http://trid.trb.org/view.aspx?id=1288303},
number = {14-2411},
year = {2014}
}
@comment{{Jonathan Aguero-Valverde PAPERS}}
@article{Wu201486,
title = {Relating crash frequency and severity: Evaluating the effectiveness of shoulder rumble strips on reducing fatal and major injury crashes },
journal = {Accident Analysis & Prevention },
volume = {67},
number = {0},
pages = {86 - 95},
year = {2014},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2014.02.004},
url = {http://www.sciencedirect.com/science/article/pii/S0001457514000438},
author = {Kun-Feng Wu and Eric T. Donnell and Jonathan Aguero-Valverde},
keywords = {Crash severity},
keywords = {Shoulder rumble strips},
keywords = {Fixed-effects model},
keywords = {Heavy trucks},
keywords = {Motorcycles},
keywords = {Pedestrians },
abstract = {Abstract To approach the goal of “Toward Zero Deaths,” there is a need to develop an analysis paradigm to better understand the effects of a countermeasure on reducing the number of severe crashes. One of the goals in traffic safety research is to search for an effective treatment to reduce fatal and major injury crashes, referred to as severe crashes. To achieve this goal, the selection of promising countermeasures is of utmost importance, and relies on the effectiveness of candidate countermeasures in reducing severe crashes. Although it is important to precisely evaluate the effectiveness of candidate countermeasures in reducing the number of severe crashes at a site, the current state-of-the-practice often leads to biased estimates. While there have been a few advanced statistical models developed to mitigate the problem in practice, these models are computationally difficult to estimate because severe crashes are dispersed spatially and temporally, and cannot be integrated into the Highway Safety Manual framework, which develops a series of safety performance functions and crash modification factors to predict the number of crashes. Crash severity outcomes are generally integrated into the Highway Safety Manual using deterministic distributions rather than statistical models. Accounting for the variability in crash severity as a function geometric design, traffic flow, and other roadway and roadside features is afforded by estimating statistical models. Therefore, there is a need to develop a new analysis paradigm to resolve the limitations in the current Highway Safety Manual methods. We propose an approach which decomposes the severe crash frequency into a function of the change in the total number of crashes and the probability of a crash becoming a severe crash before and after a countermeasure is implemented. We tested this approach by evaluating the effectiveness of shoulder rumble strips on reducing the number of severe crashes. A total of 310 segments that have had shoulder rumble strips installed during 2002–2009 are included in the analysis. It was found that shoulder rumble strips reduce the total number of crashes, but have no statistically significant effect on reducing the probability of a severe crash outcome. }
}
@article{AgueroValverde2013365,
title = {Multivariate spatial models of excess crash frequency at area level: Case of Costa Rica },
journal = {Accident Analysis & Prevention },
volume = {59},
number = {0},
pages = {365 - 373},
year = {2013},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2013.06.014},
url = {http://www.sciencedirect.com/science/article/pii/S000145751300242X},
author = {Jonathan Aguero-Valverde},
keywords = {Multivariate spatial},
keywords = {\{CAR\}},
keywords = {\{MCAR\}},
keywords = {Full Bayes },
abstract = {Abstract Recently, areal models of crash frequency have being used in the analysis of various area-wide factors affecting road crashes. On the other hand, disease mapping methods are commonly used in epidemiology to assess the relative risk of the population at different spatial units. A natural next step is to combine these two approaches to estimate the excess crash frequency at area level as a measure of absolute crash risk. Furthermore, multivariate spatial models of crash severity are explored in order to account for both frequency and severity of crashes and control for the spatial correlation frequently found in crash data. This paper aims to extent the concept of safety performance functions to be used in areal models of crash frequency. A multivariate spatial model is used for that purpose and compared to its univariate counterpart. Full Bayes hierarchical approach is used to estimate the models of crash frequency at canton level for Costa Rica. An intrinsic multivariate conditional autoregressive model is used for modeling spatial random effects. The results show that the multivariate spatial model performs better than its univariate counterpart in terms of the penalized goodness-of-fit measure Deviance Information Criteria. Additionally, the effects of the spatial smoothing due to the multivariate spatial random effects are evident in the estimation of excess equivalent property damage only crashes. }
}
@article{AgueroValverde2013289,
title = {Full Bayes Poisson gamma, Poisson lognormal, and zero inflated random effects models: Comparing the precision of crash frequency estimates },
journal = {Accident Analysis & Prevention },
volume = {50},
number = {0},
pages = {289 - 297},
year = {2013},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2012.04.019},
url = {http://www.sciencedirect.com/science/article/pii/S0001457512001522},
author = {Jonathan Aguero-Valverde},
keywords = {Full Bayes},
keywords = {Zero inflated models},
keywords = {Random effects},
keywords = {Ranking of sites },
abstract = {In recent years, complex statistical modeling approaches have being proposed to handle the unobserved heterogeneity and the excess of zeros frequently found in crash data, including random effects and zero inflated models. This research compares random effects, zero inflated, and zero inflated random effects models using a full Bayes hierarchical approach. The models are compared not just in terms of goodness-of-fit measures but also in terms of precision of posterior crash frequency estimates since the precision of these estimates is vital for ranking of sites for engineering improvement. Fixed-over-time random effects models are also compared to independent-over-time random effects models. For the crash dataset being analyzed, it was found that once the random effects are included in the zero inflated models, the probability of being in the zero state is drastically reduced, and the zero inflated models degenerate to their non zero inflated counterparts. Also by fixing the random effects over time the fit of the models and the precision of the crash frequency estimates are significantly increased. It was found that the rankings of the fixed-over-time random effects models are very consistent among them. In addition, the results show that by fixing the random effects over time, the standard errors of the crash frequency estimates are significantly reduced for the majority of the segments on the top of the ranking. }
}
@comment{{Paul P. Jovanis PAPERS}}
@article{Wu2014210,
title = {Using naturalistic driving data to explore the association between traffic safety-related events and crash risk at driver level },
journal = {Accident Analysis & Prevention },
volume = {72},
number = {0},
pages = {210 - 218},
year = {2014},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2014.07.005},
url = {http://www.sciencedirect.com/science/article/pii/S0001457514002012},
author = {Kun-Feng Wu and Jonathan Aguero-Valverde and Paul P. Jovanis},
keywords = {Naturalistic driving data},
keywords = {Surrogate events},
keywords = {Safety-related events},
keywords = {Multivariate Poisson log-normal models },
abstract = {Abstract There has been considerable research conducted over the last 40 years using traffic safety-related events to support road safety analyses. Dating back to traffic conflict studies from the 1960s these observational studies of driver behavior have been criticized due to: poor quality data; lack of available and useful exposure measures linked to the observations; the incomparability of self-reported safety-related events; and, the difficulty in assessing culpability for safety-related events. This study seeks to explore the relationships between driver characteristics and traffic safety-related events, and between traffic safety-related events and crash involvement while mitigating some of those limitations. The Virginia Tech Transportation Institute 100-Car Naturalistic Driving Study dataset, in which the participants’ vehicles were instrumented with various cameras and sensors during the study period, was used for this study. The study data set includes 90 drivers observed for 12–13 months driving. This study focuses on single vehicle run-off-road safety-related events only, including 14 crashes and 182 safety-related events (30 near crashes, and 152 crash-relevant incidents). Among the findings are: (1) drivers under age 25 are significantly more likely to be involved in safety-related events and crashes; and (2) significantly positive correlations exist between crashes, near crashes, and crash-relevant incidents. Although there is still much to learn about the factors affecting the positive correlation between safety-related events and crashes, a Bayesian multivariate Poisson log-normal model is shown to be useful to quantify the associations between safety-related events and crash risk while controlling for driver characteristics. }
}
@article{Wu201310,
title = {Defining and screening crash surrogate events using naturalistic driving data },
journal = {Accident Analysis & Prevention },
volume = {61},
number = {0},
pages = {10 - 22},
year = {2013},
note = {Emerging Research Methods and Their Application to Road Safety Emerging Issues in Safe and Sustainable Mobility for Older Persons The Candrive/Ozcandrive Prospective Older Driver Study: Methodology and Early Study Findings },
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2012.10.004},
url = {http://www.sciencedirect.com/science/article/pii/S0001457512003600},
author = {Kun-Feng Wu and Paul P. Jovanis},
keywords = {Traffic safety},
keywords = {Crash surrogate},
keywords = {Naturalistic driving study },
abstract = {Naturalistic driving studies provide an excellent opportunity to better understand crash causality and to supplement crash observations with a much larger number of near crash events. The goal of this research is the development of a set of diagnostic procedures to define, screen, and identify crash and near crash events that can be used in enhanced safety analyses. A way to better understand crash occurrence and identify potential countermeasures to improve safety is to learn from and use near crash events, particularly those near crashes that have a common etiology to crash outcomes. This paper demonstrates that a multi-stage modeling framework can be used to search through naturalistic driving data, extracting statistically similar crashes and near crashes. The procedure is tested using data from the \{VTTI\} 100-car study for road departure events. A total of 63 events are included in this application. While the sample size is limited in this empirical study, the authors believe the procedure is ready for testing in other applications. }
}
@article{Wu2012507,
title = {Crashes and crash-surrogate events: Exploratory modeling with naturalistic driving data },
journal = {Accident Analysis & Prevention },
volume = {45},
number = {0},
pages = {507 - 516},
year = {2012},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2011.09.002},
url = {http://www.sciencedirect.com/science/article/pii/S0001457511002399},
author = {Kun-Feng Wu and Paul P. Jovanis},
keywords = {Traffic safety},
keywords = {Crash surrogate},
keywords = {Naturalistic driving study data analysis },
abstract = {There is a need to extend and refine the use of crash surrogates to enhance safety analyses. This is particularly true given opportunities for data collection presented by naturalistic driving studies. This paper connects the original research on traffic conflicts to the contemporary literature concerning crash surrogates using the crash-to-surrogate ratio, π. A conceptual structure is developed in which the ratio can be estimated using either a Logit or Probit formulation which captures context and event variables as predictors in the model specification. This allows the expansion of the crash-to-surrogate concept beyond traffic conflicts to many contexts and crash types. The structure is tested using naturalistic driving data from a study conducted in the United States (Dingus et al., 2005). While the sample size is limited (13 crashes and 38 near crashes), there is reasonable correspondence between predicted and observed crash frequencies using a Logit model formulation. The paper concludes with a summary of empirical results and suggestions for future research. }
}
@article{AgueroValverde2006618,
title = {Spatial analysis of fatal and injury crashes in Pennsylvania },
journal = {Accident Analysis & Prevention },
volume = {38},
number = {3},
pages = {618 - 625},
year = {2006},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2005.12.006},
url = {http://www.sciencedirect.com/science/article/pii/S0001457505002095},
author = {Jonathan Aguero-Valverde and Paul P. Jovanis},
keywords = {Full Bayes hierarchical model},
keywords = {Spatial correlation},
keywords = {Negative binomial model},
keywords = {Crash risk},
keywords = {Weather conditions and crash risk },
abstract = {Using injury and fatal crash data for Pennsylvania for 1996–2000, full Bayes (FB) hierarchical models (with spatial and temporal effects and space–time interactions) are compared to traditional negative binomial (NB) estimates of annual county-level crash frequency. Covariates include socio-demographics, weather conditions, transportation infrastructure and amount of travel. \{FB\} hierarchical models are generally consistent with the \{NB\} estimates. Counties with a higher percentage of the population under poverty level, higher percentage of their population in age groups 0–14, 15–24, and over 64 and those with increased road mileage and road density have significantly increased crash risk. Total precipitation is significant and positive in the \{NB\} models, but not significant with FB. Spatial correlation, time trend, and space–time interactions are significant in the \{FB\} injury crash models. County-level \{FB\} models reveal the existence of spatial correlation in crash data and provide a mechanism to quantify, and reduce the effect of, this correlation. Addressing spatial correlation is likely to be even more important in road segment and intersection-level crash models, where spatial correlation is likely to be even more pronounced. }
}
@article{AbdelAty199739,
title = {Using stated preference data for studying the effect of advanced traffic information on drivers' route choice },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {5},
number = {1},
pages = {39 - 50},
year = {1997},
note = {},
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/S0968-090X(96)00023-X},
url = {http://www.sciencedirect.com/science/article/pii/S0968090X9600023X},
author = {Mohamed A. Abdel-Aty and Ryuichi Kitamura and Paul P. Jovanis},
abstract = {This paper presents a statistical analysis of commuters' route choice including the effect of traffic information. The paper utilizes data collected from two stated preference survey techniques. Two route choice models were estimated. The first model used five hypothetical binary choice sets collected in a computer-aided telephone interview. The objective of the model was to determine how travel time variation affects route choice, and the potential interplay among travel time variation, traffic information acquisition and route choice. The second model used data collected in a mail survey from three binary route choice stated preference scenarios customized according to each respondent's actual commute route and travel time. The objective of the model was to investigate the potential effect of advanced traveler information systems on route choice. The correlation among error components in repeated measurement data was addressed in this paper with individual-specific random error components in a binary logit model with normal mixing distribution. The results underscored the significance of traffic information and the potential effect of advanced traveler information systems (ATIS) on route choice. }
}
@article{Kaneko1992437,
title = {Multiday driving patterns and motor carrier accident risk: A disaggregate analysis },
journal = {Accident Analysis & Prevention },
volume = {24},
number = {5},
pages = {437 - 456},
year = {1992},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/0001-4575(92)90055-N},
url = {http://www.sciencedirect.com/science/article/pii/000145759290055N},
author = {Tetsuya Kaneko and Paul P. Jovanis},
abstract = {A method has been developed to estimate the relative accident risk posed by different patterns of driving over a multiday period. The procedure explicitly considers whether a driver is on duty or off duty for each half hour of each day during the period of analysis. From a data set of over 1,000 drivers, nine distinct driving patterns are identified. Membership in the patterns is determined exclusively by the pattern of duty hours for seven consecutive days; for some drivers an accident occurred on the eighth day while others had no accident, therefore each pattern can be associated with a relative accident risk. Additional statistical modeling allowed the consideration, in addition to driving pattern, of driver age, experience with the firm, hours off duty prior to the last trip and hours driving on the last trip (either until the accident or successful completion of the trip). The finding of the modeling is that driving patterns over the previous seven days significantly affect accident risk on the eighth day. In general, driving during the early and late morning (e.g. midnight to 10 a.m.) has the highest accident risk while all seven other multiday patterns had indistinguishable risk. Consecutive hours driven also has a significant effect on accident risk: the first hour through the fourth hour having the lowest risk with a fluctuating increase in risk to a maximum beyond nine hours. Driver age and hours off duty immediately prior to a trip do not appear to affect accident risk significantly. These findings quantitatively assess the relative accident risk of multiday driving patterns using data from actual truck operations. Further research is recommended in the areas of refining model structures, adding explanatory variables (such as highway type), and testing more complex models. }
}
@article{Moore1988257,
title = {Modelling media choices in business organizations: Implications for analyzing telecommunications-transportation interactions },
journal = {Transportation Research Part A: General },
volume = {22},
number = {4},
pages = {257 - 273},
year = {1988},
note = {},
issn = {0191-2607},
doi = {http://dx.doi.org/10.1016/0191-2607(88)90004-0},
url = {http://www.sciencedirect.com/science/article/pii/0191260788900040},
author = {Anthony Moore and Paul P Jovanis},
abstract = {A framework to analyze the impact of the new electronic communication technologies on transportation systems in the business setting has been proposed. A component of the framework that focuses on the media choice processes of individuals was empirically tested using scenarios in which the physical mail media, courier services, the telephone, voice mail, and electronic mail were alternatives to complete information communication tasks. The media choice model developed in this research emphasizes the influence of the context of the communication activity on media choice. Individual and organizational characteristics are explicitly considered, along with variables describing the communication activity itself, and the relationship between the initiator and the recipient of the communication. These characteristics determine the relative importance of a set of communication attributes and personal needs which are then matched against the individual's perceptions and feelings about the media to form preferences and choices in specific contexts. Empirical results are presented using preference logit models for a series of information communication situations. Significant variations in preferences and the levels of significance of the independent variables provided evidence of the strong influence the context of the communication activity has on media choice. Implications of these results are discussed in terms of other types of business meetings which may involve choices between telecommunications media and transportation modes. The primary contribution of this research is a methodology that can be extended to rigorously analyze telecommunications-transportation interactions. The paper discusses some of the issues that need to be addressed in modelling telecommunications-transportation interactions. }
}
@article{Chang1990407,
title = {Formulating accident occurrence as a survival process },
journal = {Accident Analysis & Prevention },
volume = {22},
number = {5},
pages = {407 - 419},
year = {1990},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/0001-4575(90)90037-L},
url = {http://www.sciencedirect.com/science/article/pii/000145759090037L},
author = {Hsin-Li Chang and Paul P. Jovanis},
abstract = {A conceptual framework for accident occurrence is developed based on the principle of the driver as an information processor. The framework underlies the development of a modeling approach that is consistent with the definition of exposure to risk as a repeated trial. Survival theory is proposed as a statistical technique that is consistent with the conceptual structure and allows the exploration of a wide range of factors that contribute to highway operating risk. This survival model of accident occurrence is developed at a disaggregate level, allowing safety researchers to broaden the scope of studies which may be limited by the use of traditional aggregate approaches. An application of the approach to motor carrier safety is discussed as are potential applications to a variety of transportation industries. Lastly, a typology of highway safety research methodologies is developed to compare the properties of four safety methodologies: laboratory experiments, on-the-road studies, multidisciplinary accident investigations, and correlational studies. The survival theory formulation has a mathematical structure that is compatible with each safety methodology, so it may facilitate the integration of findings across methodologies. }
}
@article{Jovanis1989445,
title = {Disaggregate model of highway accident occurrence using survival theory },
journal = {Accident Analysis & Prevention },
volume = {21},
number = {5},
pages = {445 - 458},
year = {1989},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/0001-4575(89)90005-5},
url = {http://www.sciencedirect.com/science/article/pii/0001457589900055},
author = {Paul P. Jovanis and Hsin-Li Chang},
abstract = {The analysis of discrete accident data and aggregate exposure data frequently necessitates compromises that can obscure the relationship between accident occurrence and potential causal risk components. One way to overcome these difficulties is to develop a model of accident occurrence that includes accident and exposure data at a mathematically consistent disaggregate level. This paper describes the conceptual and mathematical development of such a model using principals of survival theory. The model predicts the probability of being involved in an accident at time t given that a vehicle has survived until that time. Several alternative functional forms are discussed including additive, proportional hazards and accelerated failure time models. Model estimation is discussed for the case in which both accident and nonaccident trips are included and for the case with only accident data. As formulated, the model has the distinct advantage of being able to consider accident and exposure data at a disaggregate level in an entirely consistent analytic framework. A conditional accident analysis is undertaken using truck accident data obtained from a major national carrier in the United States. Model results are interpretable and generally reasonable. Of particular interest is that segmenting accidents in several categories yields very different sets of significant parameters. Driver service hours seemed to most strongly effect accident risk: regularly scheduled drivers who take frequent trips are likely to have a reduced risk of an accident, particularly if they have a longer (greater than eight) number of hours off-duty just prior to a trip. }
}
@article{Srinivasan199473,
title = {Simulation study of driving performance with selected route guidance systems },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {2},
number = {2},
pages = {73 - 90},
year = {1994},
note = {},
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/0968-090X(94)90001-9},
url = {http://www.sciencedirect.com/science/article/pii/0968090X94900019},
author = {Raghavan Srinivasan and Chun-Zin Yang and Paul P. Jovanis and Ryuichi Kitamura and Mohammad Anwar},
abstract = {Experiments were conducted in a driving simulator developed by the Hughes Aircraft Corporation to study the human factors aspects of route guidance systems. The primary objective of this research was to study how in-vehicle route guidance system attributes, driver characteristics, and traffic conditions affect driving performance. Four types of route guidance systems were tested. They are: (1) Paper Map, (2) Heads Down Electronic Map, (3) Heads Up Display (HUD) in combination with Electronic Map, and (4) Voice Guidance in combination with Electronic Map. Data were collected for a total of 18 subjects, 9 male and 9 female. All subjects were tested in all four route guidance systems. The following performance measures were collected in the simulator: Number of Navigation Errors and Reaction times to external events. Apart from these, an unobstrusive eye tracker was also used to monitor eye fixations. Data were also collected on driver preferences and subjective workload associated with each of the four route guidance systems. The results of the study can be summarized as follows: (a) Subjective workload, user perceptions, eye tracker dwelling times, and number of errors all indicated that the voice guidance/electronic map combination performed the best, and the paper map the worst. The electronic map was found to be the second best, closely followed by the \{HUD\} electronic map. (b) The reaction time modelling yielded slightly different device performance depending on the event being reacted to. The heads up display/electronic map combination performed much better in comparison to its performance in the other performance measures, with voice/electronic map also doing well. The paper map again consistently performed the worst. (c) Driving performance did vary with gender and experience. Not surprisingly, drivers with higher experience performed better than drivers with lower experience. This effect was more prominent among females than males. }
}
@article{Christoffel198625,
title = {Childhood pedestrian injury: A pilot study concerning etiology },
journal = {Accident Analysis & Prevention },
volume = {18},
number = {1},
pages = {25 - 35},
year = {1986},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/0001-4575(86)90033-3},
url = {http://www.sciencedirect.com/science/article/pii/0001457586900333},
author = {Katherine K. Christoffel and Joseph L. Schofer and Paul P. Jovanis and Barbara Brandt and Barbara White and Robert Tanz},
abstract = {For U.S. children of preschool and school age, fatal pedestrian injury is more common than fatal passenger injury, but there is no agreement on preventive approaches and their efficacy. Development of preventive measures requires understanding of how and why such injuries occur, which in turn requires better methods to sort out the many factors which appear to contribute to the problem. In an attempt to develop the broadest possible picture of the dynamics of child pedestrian injury, a multidisciplinary process was developed to collect and interpret medical, traffic, social, psychological and behavioral information concerning specific injury events. In a pilot study, the process was used to study six pedestrian injuries. The pilot study indicated that: (1) the multidisciplinary approach identified possible etiologic factors missed without it; (2) this approach requires the availability of high quality medical information and police accident records; (3) biological, psychological, and social characteristics of victims, victim families and communities appear to affect the occurrence of child pedestrian injuries; and, (4) such victim factors must be considered in development of countermeasures. It is concluded that the technique of multidisciplinary analysis merits further application as a productive way to generate quantitatively testable hypotheses concerning childhood pedestrian injury causality and potential countermeasures. }
}
@incollection{Jovanis1978207,
title = {\{PLANNING\} \{CONSEQUENCES\} \{OF\} \{TRAFFIC\} \{SYSTEMS\} \{MANAGEMENT\} },
editor = {INOUE, T. HASEGAWAK. },
booktitle = {Urban, Regional and National Planning (UNRENAP) },
publisher = {Pergamon},
edition = {},
address = {},
year = {1978},
pages = {207 - 215},
isbn = {978-0-08-022013-0},
doi = {http://dx.doi.org/10.1016/B978-0-08-022013-0.50035-1},
url = {http://www.sciencedirect.com/science/article/pii/B9780080220130500351},
author = {Paul P. Jovanis and Adolf D. May},
abstract = {\{ABSTRACT\} The traffic network model, \{TRANSYT\} 6, has been modified to include fuel consumption and vehicle emission impacts, as well as modal and spatial demand responses. Tests on a 5-mile section at Wilshire Boulevard in Los Angeles indicate that the most promising strategies from an environmental and passenger productivity viewpoint appear to be exclusive bus lanes and signal optimization on a passenger basis. Further tests under varying conditions are needed before traffic management guidelines can be established. }
}
@comment{{Panagiotis Ch. Anastasopoulos PAPERS}}
@article{Anastasopoulos2010136,
title = {Contracting in highway maintenance and rehabilitation: Are spatial effects important? },
journal = {Transportation Research Part A: Policy and Practice },
volume = {44},
number = {3},
pages = {136 - 146},
year = {2010},
note = {},
issn = {0965-8564},
doi = {http://dx.doi.org/10.1016/j.tra.2009.12.002},
url = {http://www.sciencedirect.com/science/article/pii/S0965856409001281},
author = {Panagiotis Ch. Anastasopoulos and Raymond J.G.M. Florax and Samuel Labi and Mathew G. Karlaftis},
keywords = {Innovative outsourcing},
keywords = {Infrastructure maintenance},
keywords = {Rehabilitation},
keywords = {Cost savings},
keywords = {Contract management},
keywords = {Spatial econometric analysis },
abstract = {Highway agencies around the world strive to improve practices for infrastructure maintenance and rehabilitation, using project delivery policies that range from total ‘in-house’ responsibility to complete privatization, with a number of flexible contracting policies such as performance-based contracting, variants of design-build-maintain, and lane rentals among others between these two extremes. In this paper, we present a methodology that duly accounts for underlying spatial effects and estimates the expected cost savings of innovative contracting policies for highway maintenance and rehabilitation relative to in-house execution of these activities. Spatial econometric modeling is used to analyze highway contract data from 49 countries. We also investigate the marginal effects of key explanatory variables on contract cost savings using spatial multipliers. Our findings show that there are significant relationships between cost savings and contract characteristics, and that there is an apparent direct relationship between the average cost savings of contracts in a country and contract average cost savings and contract sizes in neighboring countries. }
}
@comment{{Peter T. Savolainen PAPERS}}
@article{Russo2014137e1,
title = {Assessing characteristics related to the use of seatbelts and cell phones by drivers: Application of a bivariate probit model },
journal = {Journal of Safety Research },
volume = {49},
number = {0},
pages = {137.e1 - 142},
year = {2014},
note = {Proceedings of the International Conference on Road Safety (RSS2013) International Conference on Road Safety },
issn = {0022-4375},
doi = {http://dx.doi.org/10.1016/j.jsr.2014.03.001},
url = {http://www.sciencedirect.com/science/article/pii/S002243751400019X},
author = {Brendan J. Russo and Jonathan J. Kay and Peter T. Savolainen and Timothy J. Gates},
keywords = {Cell phones},
keywords = {Safety belts},
keywords = {Driver behavior},
keywords = {Bivariate probit },
abstract = {AbstractIntroduction The effects of cell phone use and safety belt use have been an important focus of research related to driver safety. Cell phone use has been shown to be a significant source of driver distraction contributing to substantial degradations in driver performance, while safety belts have been demonstrated to play a vital role in mitigating injuries to crash-involved occupants. Method This study examines the prevalence of cell phone use and safety belt non-use among the driving population through direct observation surveys. A bivariate probit model is developed to simultaneously examine the factors that affect cell phone and safety belt use among motor vehicle drivers. Results The results show that several factors may influence drivers' decision to use cell phones and safety belts, and that these decisions are correlated. Practical applications Understanding the factors that affect both cell phone use and safety belt non-use is essential to targeting policy and programs that reduce such behavior. }
}
@article{Russo201421,
title = {Comparison of factors affecting injury severity in angle collisions by fault status using a random parameters bivariate ordered probit model },
journal = {Analytic Methods in Accident Research },
volume = {2},
number = {0},
pages = {21 - 29},
year = {2014},
note = {},
issn = {2213-6657},
doi = {http://dx.doi.org/10.1016/j.amar.2014.03.001},
url = {http://www.sciencedirect.com/science/article/pii/S2213665714000189},
author = {Brendan J. Russo and Peter T. Savolainen and William H. Schneider IV and Panagiotis Ch. Anastasopoulos},
keywords = {Crash severity},
keywords = {Intersection crash},
keywords = {Fault status},
keywords = {Random parameter bivariate ordered probit },
abstract = {Abstract The extant traffic safety research literature includes numerous examples of studies that assess those factors affecting the degree of injury sustained by crash-involved motor vehicle occupants. One important methodological concern in such work is the potential correlation in injury outcomes among occupants involved in the same crash, which may be due to common unobserved factors affecting such occupants. A second concern is unobserved heterogeneity, which is reflective of parameter effects that vary across individuals and crashes. To address these concerns, a random parameters bivariate ordered probit model is estimated to examine factors affecting the degree of injury sustained by drivers involved in angle collisions. The modeling framework distinguishes between the effects of relevant factors on the injury outcomes of the at-fault and not-at-fault parties. The methodological approach allows for consideration of within-crash correlation, as well as unobserved heterogeneity, and results in significantly improved fit as compared to a series of independent models with fixed parameters. While the factors affecting injury severity are found to be similar for both drivers, the magnitudes of these effects vary between the at-fault and not-at-fault drivers. The results demonstrate that injury severity outcomes are correlated for drivers involved in the same crash. Further, the impacts of specific factors may be over- or under-estimated if such correlation is not accounted for explicitly as a part of the analysis. Various factors are found to affect driver injury severity and the random parameters framework shows these effects to vary across crashes and individuals. The analytical approach utilized provides a useful framework for injury severity analysis. }
}
@article{Maistros2014129e1,
title = {A comparison of contributing factors between alcohol related single vehicle motorcycle and car crashes },
journal = {Journal of Safety Research },
volume = {49},
number = {0},
pages = {129.e1 - 135},
year = {2014},
note = {Proceedings of the International Conference on Road Safety (RSS2013) International Conference on Road Safety },
issn = {0022-4375},
doi = {http://dx.doi.org/10.1016/j.jsr.2014.03.002},
url = {http://www.sciencedirect.com/science/article/pii/S0022437514000334},
author = {Alexander Maistros and William H. Schneider IV and Peter T. Savolainen},
keywords = {Alcohol},
keywords = {Motorcycle},
keywords = {Crash},
keywords = {Mixed logit },
abstract = {\{ABSTRACTIntroduction\} Alcohol related crashes have accounted for approximately 35% of fatal crashes per year since 1994 nationwide, with approximately 30% involving impairment over the legal blood alcohol content limit of 0.08%. Educational campaigns and law enforcement efforts are two components of multi-faceted programs aimed toward reducing impaired driving. It is crucial that further research be conducted to guide the implementation of enforcement and educational programs. Method This research attempts to provide such guidance by examining differences in alcohol-involved crashes involving motorcycles and passenger cars. Prior safety research has shown that motorcyclists follow a significantly different culture than the average passenger car operator. These cultural differences may be reflected by differences in the contributing factors affecting crashes and the severity of the resulting injuries sustained by the driver or motorcyclist. This research is focused on single-vehicle crashes only, in order to isolate modal effects from the contribution of additional vehicles. The crash data provided for this study are from the Ohio Department of Public Safety from 2009 through 2012. Results The injury severity data are analysed through the development of two mixed logit models, one for motorcyclists and one for passenger car drivers. The models quantify the effects of various factors, including horizontal curves, speeds, seatbelt use, and helmet use, which indicate that the required motor skills and balance needed for proper motorcycle operation compounded with a lack of mechanical protection make motorcyclists more prone to severe injuries, particularly on curves and in collisions with roadside objects. Practical Applications The findings of this study have been incorporated into combined motorcycle and sober driving educational safety campaigns. The results have shown to be favorable in supporting national campaign messages with local justification and backing. }
}
@article{Kay201492,
title = {Driver behavior during bicycle passing maneuvers in response to a Share the Road sign treatment },
journal = {Accident Analysis & Prevention },
volume = {70},
number = {0},
pages = {92 - 99},
year = {2014},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2014.03.009},
url = {http://www.sciencedirect.com/science/article/pii/S000145751400075X},
author = {Jonathan J. Kay and Peter T. Savolainen and Timothy J. Gates and Tapan K. Datta},
keywords = {Bicycle safety},
keywords = {Share the Road sign},
keywords = {Centerline rumble strips},
keywords = {Bicycle passing event},
keywords = {Driver behavior },
abstract = {Abstract The interaction of motorists and bicyclists, particularly during passing maneuvers, is an area of concern to the bicycle safety community as there is a general perception that motor vehicle drivers may not share the road effectively with bicyclists. This is a particular concern on road sections with centerline rumble strips where motorists are prone to crowd bicyclists during passing events. One potential countermeasure to address this concern is the use of a bicycle warning sign with a “Share the Road” plaque. This paper presents the results of a controlled field evaluation of this sign treatment, which involved an examination of driver behavior while overtaking bicyclists. A series of field studies were conducted concurrently on two segments of a high-speed, rural two-lane highway. These segments were similar in terms of roadway geometry, traffic volumes, and other relevant factors, except that one of the segments included centerline rumble strips while the other did not. A before-and-after study design was utilized to examine changes in motor vehicle lateral placement and speed at the time of the passing event as they relate to the presence of centerline rumble strips and the sign treatment. Centerline rumble strips generally shifted vehicles closer to the bicyclists during passing maneuvers, though the magnitude of this effect was marginal. The sign treatment was found to shift motor vehicles away from the rightmost lane positions, though the signs did not significantly affect the mean buffer distance between the bicyclists and passing motorists or the propensity of crowding events during passing. The sign treatment also resulted in a 2.5 miles/h (4.0 km/h) reduction in vehicle speeds. Vehicle type, bicyclist position, and the presence of opposing traffic were also found to affect lateral placement and speed selection during passing maneuvers. }
}
@article{SchneiderIV2012669,
title = {Examination of factors determining fault in two-vehicle motorcycle crashes },
journal = {Accident Analysis & Prevention },
volume = {45},
number = {0},
pages = {669 - 676},
year = {2012},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2011.09.037},
url = {http://www.sciencedirect.com/science/article/pii/S0001457511002740},
author = {William H. Schneider IV and Peter T. Savolainen and Dan Van Boxel and Rick Beverley},
keywords = {Fault},
keywords = {At-fault},
keywords = {Multivariate probit},
keywords = {Motorcyclist safety},
keywords = {Motorcycle crash },
abstract = {Motorcycle crashes frequently involve a combination of high-risk behaviors by the motorcyclist or the other crash-involved driver. Such behaviors may include riding or driving without appropriate licensure or while under the influence of alcohol, as well as deciding not to use a safety device such as a helmet or safety belt. Given that these factors frequently occur in combination with one another, it is difficult to untangle the specific effects of individual factors leading up to the crash outcome. This study assesses how various rider-, driver-, and other crash-specific factors contribute to at-fault status in two-vehicle motorcycle crashes, as well as how these same factors affect the propensity for other high-risk behaviors. Furthermore, the interrelationships among fault status and these other behaviors are also examined using a multivariate probit model. This model is developed using police-reported crash data for the years 2006–2010 from the State of Ohio. The results show that younger motorcyclists are more likely to be at-fault in the event of a collision, as are riders who are under the influence of alcohol, riding without insurance, or not wearing a helmet. Similarly, motorcyclists were less likely to be at-fault when the other driver was of younger age or was driving under the influence of alcohol, without insurance, or not wearing their safety belt. Crash-involved parties who engaged in one high-risk behavior were more likely to engage in other such behaviors, as well, and this finding was consistent for both motorcyclists and drivers. The results of this study suggest that educational and enforcement strategies aimed at addressing any one of these behaviors are likely to have tangential impacts on the other behaviors, as well. }
}
@article{Moore2011621,
title = {Mixed logit analysis of bicyclist injury severity resulting from motor vehicle crashes at intersection and non-intersection locations },
journal = {Accident Analysis & Prevention },
volume = {43},
number = {3},
pages = {621 - 630},
year = {2011},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2010.09.015},
url = {http://www.sciencedirect.com/science/article/pii/S0001457510002782},
author = {Darren N. Moore and William H. Schneider IV and Peter T. Savolainen and Mohamadreza Farzaneh},
keywords = {Injury severity},
keywords = {Mixed logit model},
keywords = {Bicyclist safety },
abstract = {Standard multinomial logit (MNL) and mixed logit (MXL) models are developed to estimate the degree of influence that bicyclist, driver, motor vehicle, geometric, environmental, and crash type characteristics have on bicyclist injury severity, classified as property damage only, possible, nonincapacitating or severe (i.e., incapacitating or fatal) injury. This study is based on 10,029 bicycleinvolved crashes that occurred in the State of Ohio from 2002 to 2008. Results of likelihood ratio tests reveal that some of the factors affecting bicyclist injury severity at intersection and non-intersection locations are substantively different and using a common model to jointly estimate impacts on severity at both types of locations may result in biased or inconsistent estimates. Consequently, separate models are developed to independently assess the impacts of various factors on the degree of bicyclist injury severity resulting from crashes at intersection and non-intersection locations. Several covariates are found to have similar impacts on injury severity at both intersection and non-intersection locations. Conversely, six variables were found to significantly influence injury severity at intersection locations but not non-intersection locations while four variables influenced bicyclist injury severity only at non-intersection locations. In crashes occurring at intersection locations, the likelihood of severe bicyclist injury increases by 14.8 percent if the bicyclist is not wearing a helmet, 82.2 percent if the motorist is under the influence of alcohol, 141.3 percent if the crash-involved motor vehicle is a van, 40.6 percent if the motor vehicle strikes the side of the bicycle, and 182.6 percent if the crash occurs on a horizontal curve with a grade. Results from non-intersection locations show the likelihood of severe injuries increases by 374.5 percent if the bicyclist is under the influence of drugs, 150.1 percent if the motorist is under the influence of alcohol, 53.5 percent if the motor vehicle strikes the side of the bicycle and 99.9 percent if the crash-involved motor vehicle is a heavy-duty truck. }
}
@comment{{Mohammed A. Quddus PAPERS}}
@article{Wang2013264,
title = {The effect of traffic and road characteristics on road safety: A review and future research direction },
journal = {Safety Science },
volume = {57},
number = {0},
pages = {264 - 275},
year = {2013},
note = {},
issn = {0925-7535},
doi = {http://dx.doi.org/10.1016/j.ssci.2013.02.012},
url = {http://www.sciencedirect.com/science/article/pii/S092575351300060X},
author = {Chao Wang and Mohammed A. Quddus and Stephen G. Ison},
abstract = {Understanding factors affecting road accidents is an important area in road safety research. This paper provides a review of the factors, with specific focus on traffic and road related factors mainly for car accidents on major roads. This paper also offers an overview of road safety theories that explain how and why these factors affect road traffic accidents. This paper offers the road safety community with a better understanding of road accidents and aids in developing suitable methods and policies for road safety improvement. Several factors most notably: speed, congestion, and road horizontal curvature were found to have mixed effects on road safety and need further examination. Future research directions on the effect of factors are also developed most notably improving the quality of data, exploring the factors in developing counties and rural areas, and employing advanced statistical models. There is also a need to further investigate issues relating to the effect of speed and congestion on road accidents, whether curvature improves road safety, and the use of more sophisticated statistical models so as to better understand the effect of factors on road accidents. }
}
@article{Ryley2014364,
title = {Investigating the contribution of Demand Responsive Transport to a sustainable local public transport system },
journal = {Research in Transportation Economics },
volume = {48},
number = {0},
pages = {364 - 372},
year = {2014},
note = {Competition and Ownership in Land Passenger Transport (selected papers from the Thredbo 13 conference) },
issn = {0739-8859},
doi = {http://dx.doi.org/10.1016/j.retrec.2014.09.064},
url = {http://www.sciencedirect.com/science/article/pii/S073988591400105X},
author = {Tim J. Ryley and Peter A. Stanley and Marcus P. Enoch and Alberto M. Zanni and Mohammed A. Quddus},
keywords = {Demand Responsive Transport},
keywords = {Public transport},
keywords = {Sustainability },
abstract = {Abstract Various studies have advocated the potential for Demand Responsive Transport (DRT) services to deliver sustainable local public transport. This paper investigates the sustainability credentials of \{DRT\} services using evidence from UK-based research. More specifically, six potential \{DRT\} market niches were identified, including those which offer potential commercial opportunities (e.g. airport surface access) and those that meet social needs (e.g. non-emergency hospital trips). Mode share of these \{DRT\} services, against car or bus travel, was simulated from mixed logit models within a panel data modelling framework estimated from survey data. The survey was conducted of over 400 respondents in urban (Rochdale, Manchester) and rural (Melton Mowbray, Leicestershire) areas. Experience shows that it is particularly difficult to make \{DRT\} services financially viable. Of the \{DRT\} services investigated, those targeting airline or train passengers offer potential. However, they are in direct competition with the car, and so their success depends on the cost and availability of parking spaces. Some of the \{DRT\} schemes explored meet social needs, such as to access shopping facilities or hospitals, but they face cost challenges. In addition, institutional barriers for new \{DRT\} schemes need to be overcome in order to develop a sustainable local public transport system. }
}
@article{Wang20111979,
title = {Predicting accident frequency at their severity levels and its application in site ranking using a two-stage mixed multivariate model },
journal = {Accident Analysis & Prevention },
volume = {43},
number = {6},
pages = {1979 - 1990},
year = {2011},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2011.05.016},
url = {http://www.sciencedirect.com/science/article/pii/S0001457511001357},
author = {Chao Wang and Mohammed A. Quddus and Stephen G. Ison},
keywords = {Road accidents},
keywords = {Site ranking},
keywords = {Bayesian spatial model},
keywords = {Mixed logit model},
keywords = {Two-stage mixed multivariate model },
abstract = {Accident prediction models (APMs) have been extensively used in site ranking with the objective of identifying accident hotspots. Previously this has been achieved by using a univariate count data or a multivariate count data model (e.g. multivariate Poisson-lognormal) for modelling the number of accidents at different severity levels simultaneously. This paper proposes an alternative method to estimate accident frequency at different severity levels, namely the two-stage mixed multivariate model which combines both accident frequency and severity models. The accident, traffic and road characteristics data from the \{M25\} motorway and surrounding major roads in England have been collected to demonstrate the use of the two-stage model. A Bayesian spatial model and a mixed logit model have been employed at each stage for accident frequency and severity analysis respectively, and the results combined to produce estimation of the number of accidents at different severity levels. Based on the results from the two-stage model, the accident hotspots on the \{M25\} and surround have been identified. The ranking result using the two-stage model has also been compared with other ranking methods, such as the naïve ranking method, multivariate Poisson-lognormal and fixed proportion method. Compared to the traditional frequency based analysis, the two-stage model has the advantage in that it utilises more detailed individual accident level data and is able to predict low frequency accidents (such as fatal accidents). Therefore, the two-stage mixed multivariate model is a promising tool in predicting accident frequency according to their severity levels and site ranking. }
}
@article{Chi2013154,
title = {Gasoline price effects on traffic safety in urban and rural areas: Evidence from Minnesota, 1998–2007 },
journal = {Safety Science },
volume = {59},
number = {0},
pages = {154 - 162},
year = {2013},
note = {},
issn = {0925-7535},
doi = {http://dx.doi.org/10.1016/j.ssci.2013.05.012},
url = {http://www.sciencedirect.com/science/article/pii/S0925753513001276},
author = {Guangqing Chi and Mohammed A. Quddus and Arthur Huang and David Levinson},
keywords = {Gasoline prices},
keywords = {Traffic safety},
keywords = {Urban–rural difference},
keywords = {Traffic crashes },
abstract = {Abstract A large literature base has found that economic factors have important effects on traffic crashes. A small but growing branch of literature also examines the role of gasoline prices in the occurrence of traffic crashes. However, no studies have investigated the possible difference of these effects between urban and rural areas. In this study, we used the monthly traffic crash data from 1998 to 2007 at the county level in Minnesota to investigate the possibly different effects gasoline prices may have on traffic crashes per million vehicle miles traveled in urban versus rural areas. The results indicate that gasoline price effects on total crashes, property-damage-only crashes, and injury crashes are stronger in rural areas than in urban areas. Gasoline prices also significantly affect fatal crashes in both urban and rural areas; however, the difference is not significant. The results concerning the differences between urban and rural areas have important policy implications for traffic safety planners and decision makers. }
}
@article{Wang2009798,
title = {Impact of traffic congestion on road accidents: A spatial analysis of the \{M25\} motorway in England },
journal = {Accident Analysis & Prevention },
volume = {41},
number = {4},
pages = {798 - 808},
year = {2009},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2009.04.002},
url = {http://www.sciencedirect.com/science/article/pii/S0001457509000797},
author = {Chao Wang and Mohammed A. Quddus and Stephen G. Ison},
keywords = {\{GIS\}},
keywords = {Traffic congestion},
keywords = {Road accidents},
keywords = {Spatial modeling},
keywords = {\{M25\} motorway },
abstract = {Traffic congestion and road accidents are two external costs of transport and the reduction of their impacts is often one of the primary objectives for transport policy makers. The relationship between traffic congestion and road accidents however is not apparent and less studied. It is speculated that there may be an inverse relationship between traffic congestion and road accidents, and as such this poses a potential dilemma for transport policy makers. This study aims to explore the impact of traffic congestion on the frequency of road accidents using a spatial analysis approach, while controlling for other relevant factors that may affect road accidents. The \{M25\} London orbital motorway, divided into 70 segments, was chosen to conduct this study and relevant data on road accidents, traffic and road characteristics were collected. A robust technique has been developed to map \{M25\} accidents onto its segments. Since existing studies have often used a proxy to measure the level of congestion, this study has employed a precise congestion measurement. A series of Poisson based non-spatial (such as Poisson-lognormal and Poisson-gamma) and spatial (Poisson-lognormal with conditional autoregressive priors) models have been used to account for the effects of both heterogeneity and spatial correlation. The results suggest that traffic congestion has little or no impact on the frequency of road accidents on the \{M25\} motorway. All other relevant factors have provided results consistent with existing studies. }
}
@article{Schmöcker2008257,
title = {Mode choice of older and disabled people: a case study of shopping trips in London },
journal = {Journal of Transport Geography },
volume = {16},
number = {4},
pages = {257 - 267},
year = {2008},
note = {},
issn = {0966-6923},
doi = {http://dx.doi.org/10.1016/j.jtrangeo.2007.07.002},
url = {http://www.sciencedirect.com/science/article/pii/S0966692307000749},
author = {Jan-Dirk Schmöcker and Mohammed A. Quddus and Robert B. Noland and Michael G.H. Bell},
keywords = {Transport mode choice},
keywords = {Disability},
keywords = {Seniors},
keywords = {Variable travel costs},
keywords = {Accessibility },
abstract = {This paper attempts to understand mode choice decisions among older and disabled people in London, with the objective of determining what policies can best meet their mobility and activity needs. A literature review is followed by a description of the data sets and modelling methods used in this analysis. Two assumptions are made on the marginal costs of car usage and it is shown that large investments (car, travelcards) are not amortized in the mode choice decisions made, but that marginal costs need to be appropriately specified. Age and disability interactions are shown to influence public transport use with those with disabilities preferring not to use public transport, although if healthy, older people will use buses and trams. The preference for taxis also increases with age when there is a disability. Public transport accessibility measures were also found to be associated with increased public transport use. }
}
@article{Noland2005737,
title = {Congestion and safety: A spatial analysis of London },
journal = {Transportation Research Part A: Policy and Practice },
volume = {39},
number = {7–9},
pages = {737 - 754},
year = {2005},
note = {},
issn = {0965-8564},
doi = {http://dx.doi.org/10.1016/j.tra.2005.02.022},
url = {http://www.sciencedirect.com/science/article/pii/S0965856405000467},
author = {Robert B. Noland and Mohammed A. Quddus},
keywords = {Traffic safety},
keywords = {Pedestrian safety},
keywords = {Negative binomial model},
keywords = {\{GIS\} },
abstract = {A disaggregate spatial analysis, using enumeration district data for London was conducted with the aim of examining how congestion may affect traffic safety. It has been hypothesized that while congested traffic conditions may increase the number of vehicle crashes and interactions, their severity is normally lower than crashes under uncongested free flowing conditions. This is primarily due to the slower speeds of vehicles when congestion is present. Our analysis uses negative binomial count models to examine whether factors affecting casualties (fatalities, serious injuries and slight injuries) differed during congested time periods as opposed to uncongested time periods. We also controlled for congestion spatially using a number of proxy variables and estimated pedestrian casualty models since a large proportion of London casualties are pedestrians. Results are not conclusive. Our results suggest that road infrastructure effects may interact with congestion levels such that in London any spatial differences are largely mitigated. Some small differences are seen between the models for congested versus uncongested time periods, but no conclusive trends can be found. Our results lead us to suspect that congestion as a mitigator of crash severity is less likely to occur in urban conditions, but may still be a factor on higher speed roads and motorways. }
}
@article{Noland2004973,
title = {A spatially disaggregate analysis of road casualties in England },
journal = {Accident Analysis & Prevention },
volume = {36},
number = {6},
pages = {973 - 984},
year = {2004},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2003.11.001},
url = {http://www.sciencedirect.com/science/article/pii/S0001457503001581},
author = {Robert B. Noland and Mohammed A. Quddus},
keywords = {Transport safety},
keywords = {Negative binomial models},
keywords = {Spatial analyses},
keywords = {Geographic information systems},
keywords = {Deprivation},
keywords = {Land use },
abstract = {Spatially disaggregate ward level data for England is used in an analysis of various area-wide factors on road casualties. Data on 8414 wards was input into a geographic information system that contained data on land use types, road characteristics and road casualties. Demographic data on area-wide deprivation (the index of multiple deprivation) for each ward was also included. Negative binomial count data models were used to analyze the associations between these factors with traffic fatalities, serious injuries and slight injuries. Results suggest that urbanized areas are associated with fewer casualties (especially fatalities) while areas of higher employment density are associated with more casualties. More deprived areas tend to have higher levels of casualties, though not of motorized casualties (except slight injuries). The effect of road characteristics are less significant but there are some positive associations with the density of “A” and “B” level roads. }
}
@article{Quddus2007433,
title = {The impact of the congestion charge on the retail business in London: An econometric analysis },
journal = {Transport Policy },
volume = {14},
number = {5},
pages = {433 - 444},
year = {2007},
note = {},
issn = {0967-070X},
doi = {http://dx.doi.org/10.1016/j.tranpol.2007.04.008},
url = {http://www.sciencedirect.com/science/article/pii/S0967070X07000418},
author = {Mohammed A. Quddus and Michael G.H. Bell and Jan-Dirk Schmöcker and Achille Fonzone},
keywords = {Congestion charge},
keywords = {Retail business},
keywords = {Trend and seasonality},
keywords = {Econometric models },
abstract = {On 17 February 2003, London introduced a pioneering congestion-charging scheme. The impact on traffic was sudden and dramatic. For example, car movements within the congestion-charging zone (21 km2) were reduced by about 30%. However, the impact on other activities, such as retail business within the charged zone, is taking longer to become evident. Many unusual events happened in close succession in 2003 making it difficult to isolate the effect of any individual event on the retail sales. This paper describes a detailed study on the impact of the congestion charge (CC) on the John Lewis Oxford Street (JLOS) store, which is one of the biggest retail stores within the charged zone. The impact is estimated using descriptive analysis, forecasting methods and econometric models. The analysis is based on weekly sales data for the period January 2000 to January 2004 (three years before the \{CC\} and about one year afterwards) relating to \{JLOS\} and five other John Lewis stores in and around London. A seasonal autoregressive integrated moving average (SARIMA) model was fitted, showing that actual sales match predicted sales up to 19 January 2003 for the \{JLOS\} store but that actual sales fall consistently below predicted sales thereafter. Clearly, something changed for the \{JLOS\} store during the week after 19 January 2003 with no sign of recovery to the end of the time series. In order to isolate the effects of a range of factors on sales, econometric models were fitted. The drop in sales at the \{JLOS\} attributable to the \{CC\} was found to be 5.5% by the time-series model and 8.2% by the panel model. }
}
@article{Quddus2007312,
title = {Current map-matching algorithms for transport applications: State-of-the art and future research directions },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {15},
number = {5},
pages = {312 - 328},
year = {2007},
note = {},
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/j.trc.2007.05.002},
url = {http://www.sciencedirect.com/science/article/pii/S0968090X07000265},
author = {Mohammed A. Quddus and Washington Y. Ochieng and Robert B. Noland},
keywords = {Map-matching},
keywords = {Transport applications},
keywords = {Research directions },
abstract = {Map-matching algorithms integrate positioning data with spatial road network data (roadway centrelines) to identify the correct link on which a vehicle is travelling and to determine the location of a vehicle on a link. A map-matching algorithm could be used as a key component to improve the performance of systems that support the navigation function of intelligent transport systems (ITS). The required horizontal positioning accuracy of such \{ITS\} applications is in the range of 1 m to 40 m (95%) with relatively stringent requirements placed on integrity (quality), continuity and system availability. A number of map-matching algorithms have been developed by researchers around the world using different techniques such as topological analysis of spatial road network data, probabilistic theory, Kalman filter, fuzzy logic, and belief theory. The performances of these algorithms have improved over the years due to the application of advanced techniques in the map matching processes and improvements in the quality of both positioning and spatial road network data. However, these algorithms are not always capable of supporting \{ITS\} applications with high required navigation performance, especially in difficult and complex environments such as dense urban areas. This suggests that research should be directed at identifying any constraints and limitations of existing map matching algorithms as a prerequisite for the formulation of algorithm improvements. The objectives of this paper are thus to uncover the constraints and limitations by an in-depth literature review and to recommend ideas to address them. This paper also highlights the potential impacts of the forthcoming European Galileo system and the European Geostationary Overlay Service (EGNOS) on the performance of map matching algorithms. Although not addressed in detail, the paper also presents some ideas for monitoring the integrity of map-matching algorithms. The map-matching algorithms considered in this paper are generic and do not assume knowledge of ‘future’ information (i.e. based on either cost or time). Clearly, such data would result in relatively simple map-matching algorithms. }
}
@article{Velaga2009672,
title = {Developing an enhanced weight-based topological map-matching algorithm for intelligent transport systems },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {17},
number = {6},
pages = {672 - 683},
year = {2009},
note = {},
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/j.trc.2009.05.008},
url = {http://www.sciencedirect.com/science/article/pii/S0968090X09000667},
author = {Nagendra R. Velaga and Mohammed A. Quddus and Abigail L. Bristow},
keywords = {Intelligent Transport System (ITS)},
keywords = {GPS, spatial road network},
keywords = {Optimisation},
keywords = {Topological map-matching },
abstract = {Map-matching (MM) algorithms integrate positioning data from a Global Positioning System (or a number of other positioning sensors) with a spatial road map with the aim of identifying the road segment on which a user (or a vehicle) is travelling and the location on that segment. Amongst the family of \{MM\} algorithms consisting of geometric, topological, probabilistic and advanced, topological \{MM\} (tMM) algorithms are relatively simple, easy and quick, enabling them to be implemented in real-time. Therefore, a tMM algorithm is used in many navigation devices manufactured by industry. However, existing tMM algorithms have a number of limitations which affect their performance relative to advanced \{MM\} algorithms. This paper demonstrates that it is possible by addressing these issues to significantly improve the performance of a tMM algorithm. This paper describes the development of an enhanced weight-based tMM algorithm in which the weights are determined from real-world field data using an optimisation technique. Two new weights for turn-restriction at junctions and link connectivity are introduced to improve the performance of matching, especially at junctions. A new procedure is developed for the initial map-matching process. Two consistency checks are introduced to minimise mismatches. The enhanced map-matching algorithm was tested using field data from dense urban areas and suburban areas. The algorithm identified 96.8% and 95.93% of the links correctly for positioning data collected in urban areas of central London and Washington, DC, respectively. In case of suburban area, in the west of London, the algorithm succeeded with 96.71% correct link identification with a horizontal accuracy of 9.81 m (2σ). This is superior to most existing topological \{MM\} algorithms and has the potential to support the navigation modules of many Intelligent Transport System (ITS) services. }
}
@article{Quddus20081732,
title = {Time series count data models: An empirical application to traffic accidents },
journal = {Accident Analysis & Prevention },
volume = {40},
number = {5},
pages = {1732 - 1741},
year = {2008},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2008.06.011},
url = {http://www.sciencedirect.com/science/article/pii/S0001457508001048},
author = {Mohammed A. Quddus},
keywords = {Traffic accidents},
keywords = {Time series count data},
keywords = {Integer-valued autoregressive},
keywords = {Negative binomial},
keywords = {Accident prediction models },
abstract = {Count data are primarily categorised as cross-sectional, time series, and panel. Over the past decade, Poisson and Negative Binomial (NB) models have been used widely to analyse cross-sectional and time series count data, and random effect and fixed effect Poisson and \{NB\} models have been used to analyse panel count data. However, recent literature suggests that although the underlying distributional assumptions of these models are appropriate for cross-sectional count data, they are not capable of taking into account the effect of serial correlation often found in pure time series count data. Real-valued time series models, such as the autoregressive integrated moving average (ARIMA) model, introduced by Box and Jenkins have been used in many applications over the last few decades. However, when modelling non-negative integer-valued data such as traffic accidents at a junction over time, Box and Jenkins models may be inappropriate. This is mainly due to the normality assumption of errors in the \{ARIMA\} model. Over the last few years, a new class of time series models known as integer-valued autoregressive (INAR) Poisson models, has been studied by many authors. This class of models is particularly applicable to the analysis of time series count data as these models hold the properties of Poisson regression and able to deal with serial correlation, and therefore offers an alternative to the real-valued time series models. The primary objective of this paper is to introduce the class of \{INAR\} models for the time series analysis of traffic accidents in Great Britain. Different types of time series count data are considered: aggregated time series data where both the spatial and temporal units of observation are relatively large (e.g., Great Britain and years) and disaggregated time series data where both the spatial and temporal units are relatively small (e.g., congestion charging zone and months). The performance of the \{INAR\} models is compared with the class of Box and Jenkins real-valued models. The results suggest that the performance of these two classes of models is quite similar in terms of coefficient estimates and goodness of fit for the case of aggregated time series traffic accident data. This is because the mean of the counts is high in which case the normal approximations and the \{ARIMA\} model may be satisfactory. However, the performance of \{INAR\} Poisson models is found to be much better than that of the \{ARIMA\} model for the case of the disaggregated time series traffic accident data where the counts is relatively low. The paper ends with a discussion on the limitations of \{INAR\} models to deal with the seasonality and unobserved heterogeneity. }
}
@article{Quddus20081486,
title = {Modelling area-wide count outcomes with spatial correlation and heterogeneity: An analysis of London crash data },
journal = {Accident Analysis & Prevention },
volume = {40},
number = {4},
pages = {1486 - 1497},
year = {2008},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2008.03.009},
url = {http://www.sciencedirect.com/science/article/pii/S0001457508000523},
author = {Mohammed A. Quddus},
keywords = {Spatial correlation},
keywords = {Uncorrelated heterogeneity},
keywords = {Negative binomial models},
keywords = {Classical spatial models},
keywords = {Bayesian hierarchical models },
abstract = {Count models such as negative binomial (NB) regression models are normally employed to establish a relationship between area-wide traffic crashes and the contributing factors. Since crash data are collected with reference to location measured as points in space, spatial dependence exists among the area-level crash observations. Although \{NB\} models can take account of the effect of unobserved heterogeneity (due to omitted variables in the model) among neighbourhoods, such models may not account for spatial correlation areas. It is then essential to adopt an econometric model that takes account of both spatial dependence and uncorrelated heterogeneity simultaneously among neighbouring units. In studying the spatial pattern of traffic crashes, two types of spatial models may be employed: (i) classical spatial models for higher levels of spatial aggregation such as states, counties, etc. and (ii) Bayesian hierarchical models for all spatial units, especially for smaller scale area-aggregations. Therefore, the primary objectives of this paper is to develop a series of relationships between area-wide different traffic casualties and the contributing factors associated with ward characteristics using both non-spatial models (such as \{NB\} models) and spatial models and to identify the similarities and differences among these relationships. The spatial units of the analysis are the 633 census wards from the Greater London metropolitan area. Ward-level casualty data are disaggregated by severity of the casualty (such as fatalities, serious injuries, and slight injuries) and by severity of the casualty related to various road users. The analysis implies that different ward-level factors affect traffic casualties differently. The results also suggest that Bayesian hierarchical models are more appropriate in developing a relationship between area-wide traffic crashes and the contributing factors associated with the road infrastructure, socioeconomic and traffic conditions of the area. This is because Bayesian models accurately take account of both spatial dependence and uncorrelated heterogeneity. }
}
@article{Gray2008483,
title = {Injury severity analysis of accidents involving young male drivers in Great Britain },
journal = {Journal of Safety Research },
volume = {39},
number = {5},
pages = {483 - 495},
year = {2008},
note = {},
issn = {0022-4375},
doi = {http://dx.doi.org/10.1016/j.jsr.2008.07.003},
url = {http://www.sciencedirect.com/science/article/pii/S0022437508001217},
author = {Rebecca C. Gray and Mohammed A. Quddus and Andrew Evans},
keywords = {Young male drivers},
keywords = {Severity of accidents},
keywords = {Ordered probit models},
keywords = {Safety targets},
keywords = {Safety policy },
abstract = {Introduction Young male drivers are over-represented in traffic accidents; they were involved in 14% of fatal accidents from 1991 to 2003 while holding only 8% of all drivers licenses in the UK. In this study, a subset of the \{UK\} national road accident data from 1991 to 2003 has been analyzed. The primary aim is to determine how to best use monetary and progressive resources to understand how road safety measures will reduce the severity of accidents involving young male drivers in both London and Great Britain. Method Ordered probit models were used to identify specific accident characteristics that increase the likelihood of one of three categorical outcomes of accident severity: slight, serious, or fatal. Results Characteristics found to lead to a higher likelihood of serious and fatal injuries are generally similar across Great Britain and London but are different from those predicted to lead to a higher likelihood of slight injuries. Those characteristics predicted to lead to serious and fatal injuries include driving in darkness, between Friday and Sunday, on roads with a speed limit of 60 mph, on single carriageways, overtaking, skidding, hitting an object off the carriageway, and when passing the site of a previous accident. Characteristics predicted to lead to slight injuries include driving in daylight, between Monday and Thursday, on roads with a speed limit of 30 mph or less, at a roundabout, waiting to move, and when an animal is on the carriageway. Impact on Industry These results aid the selection of policy options that are most likely to reduce the severity of accidents involving young male drivers. }
}
@article{Chi2010493,
title = {Gasoline prices and traffic safety in Mississippi },
journal = {Journal of Safety Research },
volume = {41},
number = {6},
pages = {493 - 500},
year = {2010},
note = {},
issn = {0022-4375},
doi = {http://dx.doi.org/10.1016/j.jsr.2010.10.003},
url = {http://www.sciencedirect.com/science/article/pii/S0022437510001027},
author = {Guangqing Chi and Arthur G. Cosby and Mohammed A. Quddus and Paul A. Gilbert and David Levinson},
keywords = {Gasoline prices},
keywords = {Traffic crashes},
keywords = {Traffic safety},
keywords = {Age},
keywords = {Gender},
keywords = {Race },
abstract = {Problem Limited literature suggests that gasoline prices have substantial effects on reducing fatal crashes. However, the literature focuses only on fatal crashes and does not examine the effects on all traffic crashes. Methods Mississippi traffic crash data from April 2004–December 2008 from the Mississippi Highway Patrol and regular-grade unleaded gasoline price data from the Energy Information Administration of the U.S. Department of Energy were used to investigate the effects of gasoline prices on traffic safety by age, gender, and race. Results Gasoline prices have both short-term and intermediate-term effects on reducing total traffic crashes and crashes of females, whites, and blacks. The intermediate-term effects are generally stronger than the short-term effects. Gasoline prices also have short-term effects on reducing crashes of younger drivers and intermediate-term effects on older drivers and male drivers. Impact on Industry Higher gasoline taxes reduce traffic crashes and may result in additional societal benefits. }
}
@article{Quddus2006283,
title = {Integrity of map-matching algorithms },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {14},
number = {4},
pages = {283 - 302},
year = {2006},
note = {},
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/j.trc.2006.08.004},
url = {http://www.sciencedirect.com/science/article/pii/S0968090X06000568},
author = {Mohammed A. Quddus and Washington Y. Ochieng and Robert B. Noland},
keywords = {Global positioning system},
keywords = {Digital road map},
keywords = {Map-matching},
keywords = {Integrityfuzzy logic },
abstract = {Map-matching algorithms are used to integrate positioning data with digital road network data so that vehicles can be placed on a road map. However, due to error associated with both positioning and map data, there can be a high degree of uncertainty associated with the map-matched locations. A quality indicator representing the level of confidence (integrity) in map-matched locations is essential for some Intelligent Transport System applications and could provide a warning to the user and provide a means of fast recovery from a failure. The objective of this paper is to determine an empirical method to derive the integrity of a map-matched location for three previously developed algorithms. This is achieved by formulating a metric based on various error sources associated with the positioning data and the map data. The metric ranges from 0 to 100 where 0 indicates a very high level of uncertainty in the map-matched location and 100 indicates a very low level of uncertainty. The integrity method is then tested for the three map-matching algorithms in the cases when the positioning data is from either a stand-alone global positioning system (GPS) or \{GPS\} integrated with deduced reckoning (DR) and for map data from three different scales (1:1250, 1:2500, and 1:50 000). The results suggest that the performance of the integrity method depends on the type of map-matching algorithm and the quality of the digital map data. A valid integrity warning is achieved 98.2% of the time in the case of the fuzzy logic map-matching algorithm with positioning data come from integrated GPS/DR and a digital map data with a scale of 1:2500. }
}
@article{Noland2004103,
title = {Improvements in medical care and technology and reductions in traffic-related fatalities in Great Britain },
journal = {Accident Analysis & Prevention },
volume = {36},
number = {1},
pages = {103 - 113},
year = {2004},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/S0001-4575(02)00132-X},
url = {http://www.sciencedirect.com/science/article/pii/S000145750200132X},
author = {Robert B Noland and Mohammed A Quddus},
keywords = {Transport safety},
keywords = {Health policy},
keywords = {Medical technology},
keywords = {Negative binomial model },
abstract = {Great Britain has one of the lowest levels of traffic-related fatalities in the industrialized world with a current total of about 3500 fatalities per year. Large reductions have occurred over the last 20–30 years and the government has targets of achieving another 40% reduction by 2010. This paper analyzes some of the factors that have been statistically significant in helping to achieve those reductions with a focus on improvements in medical care and technology. Using a cross-sectional time-series of regional data a fixed effects negative binomial (NB) model is estimated which includes three proxies of medical care and technology changes. These are the average length of inpatient stay in the hospital, the per-capita level of National Health Service (NHS) staff, and number of people per-capita waiting for hospital treatment. All are statistically significant with the expected sign showing that improvements in medical technology have reduced total fatalities with less of an impact from changes in medical care. Other variables are also found to be significant, including the percent of elderly people in the population, per-capita expenditure on alcohol, motorway capacity, and average vehicle age. The latter shows a surprisingly unexpected effect, with more older vehicles in a region leading to fewer fatalities. Models evaluating effects on serious and slight injuries are also estimated and serve to confirm the expected effects of medical care and technology. }
}
@article{Noland20061,
title = {Flow improvements and vehicle emissions: Effects of trip generation and emission control technology },
journal = {Transportation Research Part D: Transport and Environment },
volume = {11},
number = {1},
pages = {1 - 14},
year = {2006},
note = {},
issn = {1361-9209},
doi = {http://dx.doi.org/10.1016/j.trd.2005.06.003},
url = {http://www.sciencedirect.com/science/article/pii/S1361920905000453},
author = {Robert B. Noland and Mohammed A. Quddus},
keywords = {Vehicle emissions},
keywords = {Induced travel},
keywords = {Trip generation},
keywords = {Flow improvements},
keywords = {Micro-simulation },
abstract = {This paper examines whether road schemes that increase the availability of road space or which smooth the flow of traffic result in increased vehicle pollution. Economic theory indicates that increases in road space and the consequent decreases in travel time will tend to increase total vehicular travel, an effect known as induced travel. The net impacts on vehicle pollution have largely been a matter of conjecture with some arguing that policies to reduce congestion (by adding more road space) will reduce pollution by smoothing the flow of traffic and reducing stop and go traffic, while others argue that induced traffic will overwhelm this effect. This paper uses a micro-simulation model (VISSIM), integrated with a modal emissions model (CMEM), to evaluate the overall strategic policy question of how changes in available road capacity affects vehicle emissions. The analysis examines alternative vehicle fleets, ranging from a fleet with no emission control technology to relatively clean Tier 1 vehicles. Results show emission break-even points for CO, HC, NOx, fuel consumption and CO2. Increased traffic is found to quickly diminish any initial emission reduction benefits. }
}
@article{Quddus2002445,
title = {An analysis of motorcycle injury and vehicle damage severity using ordered probit models },
journal = {Journal of Safety Research },
volume = {33},
number = {4},
pages = {445 - 462},
year = {2002},
note = {},
issn = {0022-4375},
doi = {http://dx.doi.org/10.1016/S0022-4375(02)00051-8},
url = {http://www.sciencedirect.com/science/article/pii/S0022437502000518},
author = {Mohammed A. Quddus and Robert B. Noland and Hoong Chor Chin},
keywords = {Motorcyclists},
keywords = {Safety},
keywords = {Accident severity},
keywords = {Damage severity},
keywords = {Ordered probit model },
abstract = {Problem: Motorcycles constitute about 19% of all motorized vehicles in Singapore and are generally overrepresented in traffic accidents, accounting for 40% of total fatalities. Method: In this paper, an ordered probit model is used to examine factors that affect the injury severity of motorcycle accidents and the severity of damage to the vehicle for those crashes. Nine years of motorcycle accident data were obtained for Singapore through police reports. These data included categorical assessments of the severity of accidents based on three levels. Damage severity to the vehicle was also assessed and categorized into four levels. Categorical data of this type are best analyzed using ordered probit models because they require no assumptions regarding the ordinality of the dependent variable, which in this case is the severity score. Various models are examined to determine what factors are related to increased injury and damage severity of motorcycle accidents. Results: Factors found to lead to increases in the probability of severe injuries include the motorcyclist having non-Singaporean nationality, increased engine capacity, headlight not turned on during daytime, collisions with pedestrians and stationary objects, driving during early morning hours, having a pillion passenger, and when the motorcyclist is determined to be at fault for the accident. Factors leading to increased probability of vehicle damage include some similar factors but also show some differences, such as less damage associated with pedestrian collisions and with female drivers. In addition, it was also found that both injury severity and vehicle damage severity levels are decreasing over time. }
}
@comment{{Venky N. Shankar PAPERS}}
@article{Donnell20101436,
title = {A framework for estimating the safety effects of roadway lighting at intersections },
journal = {Safety Science },
volume = {48},
number = {10},
pages = {1436 - 1444},
year = {2010},
note = {},
issn = {0925-7535},
doi = {http://dx.doi.org/10.1016/j.ssci.2010.06.008},
url = {http://www.sciencedirect.com/science/article/pii/S0925753510001670},
author = {Eric T. Donnell and Richard J. Porter and Venkataraman N. Shankar},
keywords = {Night-to-day crash ratios},
keywords = {Lighting},
keywords = {Statistical analysis},
keywords = {Traffic safety},
keywords = {Intersections },
abstract = {National- and state-level guidance documents conclusively state that fixed lighting improves intersection safety. The sentiment is consistent with other design and safety manuals and is supported by a series of consistent safety findings; however, most published lighting-safety research is focused on rural, stop-controlled intersections and is limited by several methodological issues. The relationship between safety and intersection lighting at rural, signalized and urban locations is not as well documented. Methodological advancements in highway safety analysis justify new estimations of the safety effects of intersection lighting. This paper describes a proposed framework to estimate the safety effects of fixed lighting at a variety of intersection types and locations. Several key issues are explored including availability of relevant crash, lighting, and roadway inventory data; relevant data element structures; proposed analysis taxonomies to assess lighting-safety effects within and across different intersection classifications; specification and estimation of models to estimate expected crash frequencies during day and night; techniques to interpret model parameters, including variable elasticity; and tests of model transferability across states. A sample framework execution using Minnesota intersection data is provided. Results indicate a much lower overall safety benefit from lighting than published studies, but are consistent with estimates included in Highway Safety Manual research. }
}
@article{Yamamoto20081320,
title = {Underreporting in traffic accident data, bias in parameters and the structure of injury severity models },
journal = {Accident Analysis & Prevention },
volume = {40},
number = {4},
pages = {1320 - 1329},
year = {2008},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2007.10.016},
url = {http://www.sciencedirect.com/science/article/pii/S0001457508000237},
author = {Toshiyuki Yamamoto and Junpei Hashiji and Venkataraman N. Shankar},
keywords = {Injury severity},
keywords = {Ordered-response probit model},
keywords = {Sequential probit model},
keywords = {Underreporting },
abstract = {Injury severities in traffic accidents are usually recorded on ordinal scales, and statistical models have been applied to investigate the effects of driver factors, vehicle characteristics, road geometrics and environmental conditions on injury severity. The unknown parameters in the models are in general estimated assuming random sampling from the population. Traffic accident data however suffer from underreporting effects, especially for lower injury severities. As a result, traffic accident data can be regarded as outcome-based samples with unknown population shares of the injury severities. An outcome-based sample is overrepresented by accidents of higher severities. As a result, outcome-based samples result in biased parameters which skew our inferences on the effect of key safety variables such as safety belt usage. The pseudo-likelihood function for the case with unknown population shares, which is the same as the conditional maximum likelihood for the case with known population shares, is applied in this study to examine the effects of severity underreporting on the parameter estimates. Sequential binary probit models and ordered-response probit models of injury severity are developed and compared in this study. Sequential binary probit models assume that the factors determining the severity change according to the level of the severity itself, while ordered-response probit models assume that the same factors correlate across all levels of severity. Estimation results suggest that the sequential binary probit models outperform the ordered-response probit models, and that the coefficient estimates for lap and shoulder belt use are biased if underreporting is not considered. Mean parameter bias due to underreporting can be significant. The findings show that underreporting on the outcome dimension may induce bias in inferences on a variety of factors. In particular, if underreporting is not accounted for, the marginal impacts of a variety of factors appear to be overestimated. Fixed objects and environmental conditions are overestimated in their impact on injury severity, as is the effect of separate lap and shoulder belt use. Combined lap and shoulder belt usage appears to be unaffected. The parameter bias is most pronounced when underreporting of possible injury accidents in addition to property damage only accidents is taken into account. }
}
@article{SHANKAR200621,
title = {\{SOME\} \{INSIGHTS\} \{ON\} \{ROADWAY\} \{INFRASTRUCTURE\} \{DESIGN\} \{FOR\} \{SAFE\} \{ELDERLY\} \{PEDESTRIAN\} \{TRAVEL\} },
journal = {\{IATSS\} Research },
volume = {30},
number = {1},
pages = {21 - 26},
year = {2006},
note = {},
issn = {0386-1112},
doi = {http://dx.doi.org/10.1016/S0386-1112(14)60152-7},
url = {http://www.sciencedirect.com/science/article/pii/S0386111214601527},
author = {Venkataraman N. SHANKAR and Sittipan SITTIKARIYA and Ming-Bang SHYU},
keywords = {Pedestrians},
keywords = {Bayesian},
keywords = {Frequency},
keywords = {Severity},
keywords = {Logit },
abstract = {This paper presents insights into the relationship between road infrastructure and elderly pedestrian involvement in traffic accidents. We combine insights from empirical studies involving the probability of a pedestrian accident with insights from studies involving the probability of injuries to elderly pedestrians who are involved in vehicle-pedestrian accidents. The combined insights provide some direction to the methodology for identifying non-motorized improvements for supporting safe elderly travel. The results of the study indicate that after controlling for vehicle volumes, road infrastructure variables posing the greatest risk of pedestrian accidents in urban corridors include the presence of center turning lanes, traffic signal spacing exceeding 0.5 miles and roadway illumination. Center turning lanes indicate the presence of long corridors which may induce elderly pedestrians especially to attempt to cross roadways mid-block using center turning lane sections as refuges. Presence of traffic signals provides reduced pedestrian accident risk if the spacing is less than 0.5 miles. Especially for elderly pedestrians, the availability of protected crossings at signalized intersections is important considering the fact they cannot travel long block lengths in order to use signalized crossings. Presence of continuous roadway lighting decreases elderly pedestrian accident risk. The results also show the greatest impacts on injury severity probabilities are from the occurrence of elderly pedestrian accidents in non-intersection locations. Specifically, if elderly pedestrians are involved in marked crosswalk accidents, the probability of lower severity injury is higher; in contrast, if they are involved in unmarked, non-intersection locations such as mid-blocks, the probability of high severity injury is higher. We obtained these results through the use of Bayesian analysis. Bayesian analysis allows us to use subjective prior information on the distribution of parameters in combination with information from the observed data. The advantage of Bayesian analysis in the assessment of key road variables on safe elderly travel is that we can examine the robustness of results. }
}
@article{Yamamoto2004869,
title = {Bivariate ordered-response probit model of driver’s and passenger’s injury severities in collisions with fixed objects },
journal = {Accident Analysis & Prevention },
volume = {36},
number = {5},
pages = {869 - 876},
year = {2004},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2003.09.002},
url = {http://www.sciencedirect.com/science/article/pii/S000145750300126X},
author = {Toshiyuki Yamamoto and Venkataraman N. Shankar},
keywords = {Bivariate ordered-response probit model},
keywords = {Fixed object},
keywords = {Injury severity},
keywords = {Single-vehicle accident },
abstract = {A bivariate ordered-response probit model of driver’s and most severely injured passenger’s severity (IS) in collisions with fixed objects is developed in this study. Exact passenger’s \{IS\} is not necessarily observed, especially when only most severe injury of the accident and driver’s injury are recorded in the police reports. To accommodate passenger \{IS\} as well, we explicitly develop a partial observability model of passenger \{IS\} in multi-occupant vehicle (HOV). The model has consistent coefficients for the driver \{IS\} between single-occupant vehicle (SOV) and multiple-occupant vehicle accidents, and provides more efficient coefficient estimates by taking into account the common unobserved factors between driver and passenger IS. The results of the empirical analysis using 4-year statewide accident data in Washington State reveal the effects of driver’s characteristics, vehicle attributes, types of objects, and environmental conditions on both driver and passenger IS, and that their \{IS\} have different elasticities to some of the risk factors. }
}
@comment{{Gudmundur F. Ulfarsson PAPERS}}
@article{Meuser201517,
title = {Family reports of medically impaired drivers in Missouri: Cognitive concerns and licensing outcomes },
journal = {Accident Analysis & Prevention },
volume = {74},
number = {0},
pages = {17 - 23},
year = {2015},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2014.10.002},
url = {http://www.sciencedirect.com/science/article/pii/S0001457514002991},
author = {Thomas M. Meuser and David B. Carr and Elizabeth A. Unger and Gudmundur F. Ulfarsson},
keywords = {Older drivers},
keywords = {Family input},
keywords = {Dementia},
keywords = {Fitness-to-drive},
keywords = {Medical impairments},
keywords = {Alzheimer’s disease},
keywords = {Aging },
abstract = {Abstract This study investigated reasons why older adults (n = 689) were reported to the Driver License Bureau, Missouri Department of Revenue, by family members as potentially unfit to drive with an emphasis on cognitive concerns and associated licensing outcomes. A total of 448 drivers were reported to have some cognitive issue; common symptoms included confusion, memory loss, and becoming lost while driving. Diagnostic labels (Alzheimer’s disease (AD), cognitive impairment/dementia, brain injury/insult) were listed for 365 cases. A physician evaluation is required for license review. Of those with a diagnostic label, half (51%, n = 187) failed to submit this evaluation and almost all were de-licensed immediately. Of those evaluated by a physician, diagnostic agreement between family members and physicians was high for specific conditions (100% for AD, 97% for acute brain injury), and less so for cognitive impairment/dementia (75%). This latter finding suggests that physicians and family members may understand cognitive symptoms differently. Whether cognitively impaired or not, few family reported drivers in this sample (∼2%) retained a valid license. Family members may be in the best position to recognize when medical-functional deficits impact on driving safety, and physicians and driver licensing authorities would do well to take their observations into account with respect to older driver fitness. }
}
@article{Venkataraman2014146,
title = {Extending the Highway Safety Manual (HSM) framework for traffic safety performance evaluation },
journal = {Safety Science },
volume = {64},
number = {0},
pages = {146 - 154},
year = {2014},
note = {},
issn = {0925-7535},
doi = {http://dx.doi.org/10.1016/j.ssci.2013.12.001},
url = {http://www.sciencedirect.com/science/article/pii/S0925753513002981},
author = {Narayan S. Venkataraman and Gudmundur F. Ulfarsson and Venky N. Shankar},
keywords = {Traffic safety},
keywords = {Crash frequency analysis},
keywords = {Highway Safety Manual},
keywords = {Safety performance evaluation },
abstract = {Abstract Traffic safety performance evaluation, especially in agencies charged with safety investments, has primarily followed the methods outlined in the Highway Safety Manual (HSM). The \{HSM\} is a seminal start in ushering the field toward a systematic way of evaluating traffic safety. This paper presents a case for a more comprehensive framework to enable broader evaluation of safety performance based on a literature review of advanced methods. The presented framework integrates network-screening methods with pure outcome-based methods, multivariate fixed-parameter extensions of the \{HSM\} safety performance functions, and multivariate random parameter extensions. The paper suggests agencies should assess and choose methods for safety performance evaluation based on three criteria: (1) integrability with network-screening techniques, (2) data requirements, and (3) model predictive performance. This paper intends to help practitioners and researchers identify critical issues that underlie the establishment of comprehensive safety performance evaluation frameworks. To this end the paper discusses the pros and cons of the various methods, databases for the methods, and the importance of the methods for treatment of emerging databases such as roadside inventories. The presented framework is intended to provide guidance to state agencies in selecting safety evaluation methods given organizational constraints. }
}
@article{Venkataraman201412,
title = {A heterogeneity-in-means count model for evaluating the effects of interchange type on heterogeneous influences of interstate geometrics on crash frequencies },
journal = {Analytic Methods in Accident Research },
volume = {2},
number = {0},
pages = {12 - 20},
year = {2014},
note = {},
issn = {2213-6657},
doi = {http://dx.doi.org/10.1016/j.amar.2014.01.001},
url = {http://www.sciencedirect.com/science/article/pii/S2213665714000062},
author = {Narayan Venkataraman and Venky Shankar and Gudmundur F. Ulfarsson and Damian Deptuch},
keywords = {Heterogeneity-in-means},
keywords = {Random-parameter},
keywords = {Interchange},
keywords = {Non-interchange },
abstract = {Abstract This paper presents a heterogeneity-in-means, random-parameter negative binomial (HMRPNB) model of interchange type effects on interchange and non-interchange segment crash frequencies. For non-interchange segments, upstream and downstream type combinations were evaluated. Eight interchange types, namely, directional, semidirectional, clover, partclover, diamond, part diamond, single-point-urban-interchange (SPUI), and other were studied on the Washington State interstate system. A total of 575 interchange and 578 non-interchange segments were analyzed for the period 1999–2007. In interchange segments, semidirectional, partclover and other (excluding directional, diamond, SPUI, or fullclover) types significantly contributed to heterogeneity in the random parameter effects of average daily traffic, median continuous lighting proportion, minimum and maximum vertical gradients. Full and partial diamond types contributed to heterogeneity in the random parameter effects of median continuous lighting proportion, maximum horizontal degree of curvature, minimum and maximum vertical gradients. In non-interchange segments, the upstream type set including directional, semidirectional, and clover/collector-distributor type, and downstream set of directional, semidirectional, diamond, partclover, partdiamond and other type significantly contributed to heterogeneity in the random parameter means of total length of adjacent interchanges, two foot left shoulder width and two foot right shoulder width proportions. Statistically significant fixed parametric effects included urban/rural location, right continuous lighting proportion, proportion by length of three lane cross section, four lane cross section, three-to-four foot left shoulder, five-to-nine foot left shoulder, ten foot left shoulder, three-to-four foot right shoulder, five-to-nine foot right shoulder, and ten foot right shoulder, as well as number of horizontal curves in segment, and shortest horizontal curve length. }
}
@article{Venkataraman2013309,
title = {Random parameter models of interstate crash frequencies by severity, number of vehicles involved, collision and location type },
journal = {Accident Analysis & Prevention },
volume = {59},
number = {0},
pages = {309 - 318},
year = {2013},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2013.06.021},
url = {http://www.sciencedirect.com/science/article/pii/S0001457513002492},
author = {Narayan Venkataraman and Gudmundur F. Ulfarsson and Venky N. Shankar},
keywords = {Crash frequency aggregations},
keywords = {Heterogeneity},
keywords = {Random parameters},
keywords = {Roadway geometrics},
keywords = {Crash severities},
keywords = {Interchange },
abstract = {Abstract A nine-year (1999–2007) continuous panel of crash histories on interstates in Washington State, USA, was used to estimate random parameter negative binomial (RPNB) models for various aggregations of crashes. A total of 21 different models were assessed in terms of four ways to aggregate crashes, by: (a) severity, (b) number of vehicles involved, (c) crash type, and by (d) location characteristics. The models within these aggregations include specifications for all severities (property damage only, possible injury, evident injury, disabling injury, and fatality), number of vehicles involved (one-vehicle to five-or-more-vehicle), crash type (sideswipe, same direction, overturn, head-on, fixed object, rear-end, and other), and location types (urban interchange, rural interchange, urban non-interchange, rural non-interchange). A total of 1153 directional road segments comprising of the seven Washington State interstates were analyzed, yielding statistical models of crash frequency based on 10,377 observations. These results suggest that in general there was a significant improvement in log-likelihood when using \{RPNB\} compared to a fixed parameter negative binomial baseline model. Heterogeneity effects are most noticeable for lighting type, road curvature, and traffic volume (ADT). Median lighting or right-side lighting are linked to increased crash frequencies in many models for more than half of the road segments compared to both-sides lighting. Both-sides lighting thereby appears to generally lead to a safety improvement. Traffic volume has a random parameter but the effect is always toward increasing crash frequencies as expected. However that the effect is random shows that the effect of traffic volume on crash frequency is complex and varies by road segment. The number of lanes has a random parameter effect only in the interchange type models. The results show that road segment-specific insights into crash frequency occurrence can lead to improved design policy and project prioritization. }
}
@article{Valsson201319,
title = {A theory of the evolution of settlement structures based on identification and use of patterns: Iceland as a case study },
journal = {Futures },
volume = {54},
number = {0},
pages = {19 - 32},
year = {2013},
note = {},
issn = {0016-3287},
doi = {http://dx.doi.org/10.1016/j.futures.2013.09.008},
url = {http://www.sciencedirect.com/science/article/pii/S0016328713001213},
author = {Trausti Valsson and Gudmundur F. Ulfarsson and Sigurdur M. Gardarsson},
keywords = {Settlement patterns},
keywords = {Spatial development},
keywords = {Evolution},
keywords = {Global warming},
keywords = {Push/pull forces},
keywords = {Country planning },
abstract = {Abstract This paper presents a theory of how settlement structures originate and evolve, based on identifying drivers of change and resulting spatial settlement patterns. Climate, resources and their access, and spatial position are the primary drivers for the patterns of how settlement structures will evolve. As changes occur in these conditions the settlement structures eventually change. The method presented can be used to study how settlement structures may evolve in the future based on projections and predictions about changes in the drivers. The method is illustrated by using Iceland as a case study. The results of the case study suggest that global warming will induce a pull of settlements towards the warming highland plateau of the country because of less snow, better accessibility, and more vegetation. This will be helped by a push of settlements away from the coast towards the more elevated interior due to a rise in sea level. In Iceland, an opposite pattern – towards the coast – also applies because new transshipment harbours serving Arctic sea routes and oil resources will create a pull towards some parts of the coastline. }
}
@article{Kim20131073,
title = {Driver-injury severity in single-vehicle crashes in California: A mixed logit analysis of heterogeneity due to age and gender },
journal = {Accident Analysis & Prevention },
volume = {50},
number = {0},
pages = {1073 - 1081},
year = {2013},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2012.08.011},
url = {http://www.sciencedirect.com/science/article/pii/S0001457512002990},
author = {Joon-Ki Kim and Gudmundur F. Ulfarsson and Sungyop Kim and Venkataraman N. Shankar},
keywords = {Age},
keywords = {Gender},
keywords = {Single-vehicle},
keywords = {Heterogeneity},
keywords = {Mixed logit},
keywords = {Injury severity },
abstract = {This research develops a mixed logit model of driver-injury severity in single-vehicle crashes in California. The research especially considers the heterogeneous effects of age and gender. Older drivers (65+ years old) were found to have a random parameter with about half the population having a higher probability of a fatal injury given a crash than the comparison group of 25–64 year olds with all other factors than age kept constant. The other half of the 65+ population had a lower probability of fatal injury. Heterogeneity was also noted in vehicle age, but related to the gender of the driver, with males linked to, on average, a higher probability of fatal injury in a newer vehicle compared with females, all other factors kept constant. These effects lend support to the use of mixed logit models in injury severity research and show age and gender based population heterogeneity. Several other factors were found to significantly increase the probability of fatal injury for drivers in single-vehicle crashes, most notably: male driver, drunk driving, unsafe speed, older driver (65+) driving an older vehicle, and darkness without streetlights. }
}
@article{Valsson201291,
title = {Megapatterns of global settlement: Typology and drivers in a warming world },
journal = {Futures },
volume = {44},
number = {1},
pages = {91 - 104},
year = {2012},
note = {Special Issue: Futures Education },
issn = {0016-3287},
doi = {http://dx.doi.org/10.1016/j.futures.2011.09.001},
url = {http://www.sciencedirect.com/science/article/pii/S0016328711002278},
author = {Trausti Valsson and Gudmundur F. Ulfarsson},
abstract = {Changes in settlement structures of the world can be described as megapatterns that represent dynamic spatial trends. This paper defines and describes three types of such megapatterns that will be of major influence in shaping global settlement and activity structures in the future, given a warming climate: (1) megapatterns driven by global warming; (2) megapatterns driven by improved technology and resources, and (3) megapatterns driven by important spatial positions. The megapatterns are ordered into a typology and their individual and collective impacts are described. The major findings of this paper are: because of global warming many of the central areas of the globe will experience heat, water and pollution problems that will induce people and activities to be moved to cooler, wetter areas. As high, cool terrains, as well as the virgin Sub-Polar Regions—mostly located in Siberia, Northern Canada, Northern Scandinavia, Greenland, Alaska, Southern Argentina, and Southern Chile—start to get warmer, it will become possible to relocate water-craving industries, like agriculture and resource extraction. This will not necessarily lead to a large population shift, since relatively few workers are needed for most such operations. }
}
@article{Valsson2011450,
title = {Future changes in activity structures of the globe under a receding Arctic ice scenario },
journal = {Futures },
volume = {43},
number = {4},
pages = {450 - 459},
year = {2011},
note = {Special Issue: Community Engagement for Sustainable Urban Futures },
issn = {0016-3287},
doi = {http://dx.doi.org/10.1016/j.futures.2010.12.002},
url = {http://www.sciencedirect.com/science/article/pii/S0016328710002740},
author = {Trausti Valsson and Gudmundur F. Ulfarsson},
keywords = {Arctic shipping},
keywords = {Arctic resources},
keywords = {Evaluation mapping},
keywords = {Climate change},
keywords = {Global impact},
keywords = {Spatial system },
abstract = {Geospatial maps are here used for interpreting of what a scenario with a warming Arctic with less ice will mean for activity structures of the globe in the future. This will enable certain locations in the High North to become important activity areas. Of most consequence are the fundamental activity structures of Earth, like global shipping, world trade and oil extraction. These will be impacted as the Arctic sea routes have opened, opening up shorter shipping distances between the N-Pacific and N-Atlantic Oceans. The reduction of ice in the Arctic Ocean will also lead to ever improved access to the resources of Arctic ocean-floor and the Arctic Region—perhaps most importantly to oil and gas. The conclusions also indicate that some central regions of the globe may loose relatively, for instance in terms of global shipping. Oil-rich central areas—like the Persian Gulf area—will face losses in activity as their oil starts to dwindle. Arctic oil is now about 10% of the world production. The rate of Arctic ice reduction will influence the rate of growth in Arctic resource extraction and it will likely occur later this century. The activity and importance of the Arctic will thus grow relatively. }
}
@article{Ulfarsson20101805,
title = {Analyzing fault in pedestrian–motor vehicle crashes in North Carolina },
journal = {Accident Analysis & Prevention },
volume = {42},
number = {6},
pages = {1805 - 1813},
year = {2010},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2010.05.001},
url = {http://www.sciencedirect.com/science/article/pii/S0001457510001375},
author = {Gudmundur F. Ulfarsson and Sungyop Kim and Kathleen M. Booth},
keywords = {Fault},
keywords = {Crash},
keywords = {Pedestrian},
keywords = {Driver},
keywords = {Motor vehicle },
abstract = {Crashes between pedestrians and motor vehicles are an important traffic safety concern. This paper explores the assignment of fault in such crashes, where observed factors are associated with pedestrian at fault, driver at fault, or both at fault. The analysis is based on police reported crash data for 1997 through 2000 in North Carolina, U.S.A. The results show that pedestrians are found at fault in 59% of the crashes, drivers in 32%, and both are found at fault in 9%. The results indicate drivers need to take greater notice of pedestrians when drivers are turning, merging, and backing up as these are some of the prime factors associated with the driver being found at fault in a crash. Pedestrians must apply greater caution when crossing streets, waiting to cross, and when walking along roads, as these are correlated with pedestrians being found at fault. The results suggest a need for campaigns focused on positively affecting pedestrian street-crossing behavior in combination with added jaywalking enforcement. The results also indicate that campaigns to increase the use of pedestrian visibility improvements at night can have a significant positive impact on traffic safety. Intoxication is a concern and the results show that it is not only driver intoxication that is affecting safety, but also pedestrian intoxication. The findings show in combination with other research in the field, that results from traffic safety studies are not necessarily transferable between distant geographic locations, and that location-specific safety research needs to take place. It is also important to further study the specific effects of the design of the pedestrian environment on safety, e.g. crosswalk spacing, signal timings, etc., which together may affect pedestrian safety and pedestrian behavior. }
}
@article{Kim20081695,
title = {Age and pedestrian injury severity in motor-vehicle crashes: A heteroskedastic logit analysis },
journal = {Accident Analysis & Prevention },
volume = {40},
number = {5},
pages = {1695 - 1702},
year = {2008},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2008.06.005},
url = {http://www.sciencedirect.com/science/article/pii/S0001457508000985},
author = {Joon-Ki Kim and Gudmundur F. Ulfarsson and Venkataraman N. Shankar and Sungyop Kim},
keywords = {Age},
keywords = {Aging},
keywords = {Pedestrian},
keywords = {Injury},
keywords = {Heteroskedasticity},
keywords = {Logit},
keywords = {Accident},
keywords = {Severity },
abstract = {This research explores the injury severity of pedestrians in motor-vehicle crashes. It is hypothesized that the variance of unobserved pedestrian characteristics increases with age. In response, a heteroskedastic generalized extreme value model is used. The analysis links explanatory factors with four injury outcomes: fatal, incapacitating, non-incapacitating, and possible or no injury. Police-reported crash data between 1997 and 2000 from North Carolina, USA, are used. The results show that pedestrian age induces heteroskedasticity which affects the probability of fatal injury. The effect grows more pronounced with increasing age past 65. The heteroskedastic model provides a better fit than the multinomial logit model. Notable factors increasing the probability of fatal pedestrian injury: increasing pedestrian age, male driver, intoxicated driver (2.7 times greater probability of fatality), traffic sign, commercial area, darkness with or without streetlights (2–4 times greater probability of fatality), sport-utility vehicle, truck, freeway, two-way divided roadway, speeding-involved, off roadway, motorist turning or backing, both driver and pedestrian at fault, and pedestrian only at fault. Conversely, the probability of a fatal injury decreased: with increasing driver age, during the \{PM\} traffic peak, with traffic signal control, in inclement weather, on a curved roadway, at a crosswalk, and when walking along roadway. }
}
@article{Meuser2009246,
title = {Motor-vehicle crash history and licensing outcomes for older drivers reported as medically impaired in Missouri },
journal = {Accident Analysis & Prevention },
volume = {41},
number = {2},
pages = {246 - 252},
year = {2009},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2008.11.003},
url = {http://www.sciencedirect.com/science/article/pii/S0001457508002224},
author = {Thomas M. Meuser and David B. Carr and Gudmundur F. Ulfarsson},
keywords = {Fitness to drive},
keywords = {Aging},
keywords = {Voluntary reporting},
keywords = {Older driver},
keywords = {Crash history},
keywords = {Driver licensing},
keywords = {Medical impairment},
keywords = {Safety },
abstract = {The identification and evaluation of medically impaired drivers is an important safety issue. Medical fitness to drive is applicable to all ages but is particularly salient for older adults. Voluntary procedures, whereby various professionals and family members may report medical fitness concerns to State driver license bureaus, are common in the United States. This paper examines traffic crashes of drivers reported during 2001–2005 under the State of Missouri's voluntary reporting law (House Bill HB-1536) and the resulting licensing outcomes. Missouri's law is non-specific as to age, but the mean age of reported drivers was 80. Reports were submitted by police officers (30%), license office staff (27%), physicians (20%), family members (16%), and others (7%). The most common medical condition was dementia/cognitive (45%). Crash history for reported drivers was higher than that of controls, dating back to 1993, reaching a peak in 2001 when the crash involvement of reported drivers was 9.3% vs. 2.2% for controls—a fourfold difference. The crash involvement of reported drivers decreased rapidly after, indicating the impact of HB-1536 reporting with subsequent license revocation and to a lesser degree, mortality. Of the 4,100 reported individuals, 144 (3.5%) retained a driver's license after the process. }
}
@article{Kim2007511,
title = {Analysis of light rail rider travel behavior: Impacts of individual, built environment, and crime characteristics on transit access },
journal = {Transportation Research Part A: Policy and Practice },
volume = {41},
number = {6},
pages = {511 - 522},
year = {2007},
note = {},
issn = {0965-8564},
doi = {http://dx.doi.org/10.1016/j.tra.2006.11.001},
url = {http://www.sciencedirect.com/science/article/pii/S0965856406001455},
author = {Sungyop Kim and Gudmundur F. Ulfarsson and J. Todd Hennessy},
keywords = {Mode choice},
keywords = {Public transit},
keywords = {Light rail},
keywords = {Transit-oriented development},
keywords = {Crime},
keywords = {Transit station security },
abstract = {This paper analyzes factors that influence the mode choice for trips between home and light rail stations, an often neglected part of a person’s trip making behavior. This is important for transit planning, demand modeling, and transit oriented development. Using transit survey data describing St. Louis MetroLink riders in the United States, this study found that some of the factors associated with increased shares of walking relative to other modes were full-time student status, higher income transit riders, and trips made during the evening. It was also found that crime at stations had an impact. In particular, crime made female transit riders more likely to be picked-up/dropped-off at the station. Females are more likely to be picked-up or dropped-off at night. Bus availability and convenience showed that transit riders that have a direct bus connection to a light rail station were more likely to use the bus. Private vehicle availability was strongly associated with increased probability of drive and park, when connecting to light rail. }
}
@article{Waddell2007382,
title = {Incorporating land use in metropolitan transportation planning },
journal = {Transportation Research Part A: Policy and Practice },
volume = {41},
number = {5},
pages = {382 - 410},
year = {2007},
note = {Bridging Research and Practice: A Synthesis of Best Practices in Travel Demand Modeling },
issn = {0965-8564},
doi = {http://dx.doi.org/10.1016/j.tra.2006.09.008},
url = {http://www.sciencedirect.com/science/article/pii/S0965856406001170},
author = {Paul Waddell and Gudmundur F. Ulfarsson and Joel P. Franklin and John Lobb},
keywords = {Land use model},
keywords = {Land use – transport interaction},
keywords = {Urban simulation },
abstract = {In current practice, very few Metropolitan Planning Agencies attempt to capture the effects of transportation system changes on land use, and the consequent feedback effects on transportation system performance, despite substantial evidence that these effects may be significant. In this paper, we present a case study on the application of UrbanSim, a detailed land use simulation model system, and its integration with a regional travel demand model in the Greater Wasatch Front area of Utah. Like several other metropolitan areas, this region has recently been confronted with legal challenges to proposed highway projects, drawing substantial scrutiny to the land use-transportation connection. We describe the UrbanSim model specification, results from model estimation, and sensitivity analyses conducted with the combined land use and travel model system. The results of the sensitivity analysis suggest that accounting for the land use effects of a regional transportation plan may produce significant shifts in key transportation evaluation measures such as vehicle miles traveled, vehicle hours traveled, and hours of congestion delay. }
}
@article{Kim2007238,
title = {Bicyclist injury severities in bicycle–motor vehicle accidents },
journal = {Accident Analysis & Prevention },
volume = {39},
number = {2},
pages = {238 - 251},
year = {2007},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2006.07.002},
url = {http://www.sciencedirect.com/science/article/pii/S000145750600128X},
author = {Joon-Ki Kim and Sungyop Kim and Gudmundur F. Ulfarsson and Luis A. Porrello},
keywords = {Bicycle},
keywords = {Biking},
keywords = {Injury},
keywords = {Severity},
keywords = {Accident},
keywords = {Crash },
abstract = {This research explores the factors contributing to the injury severity of bicyclists in bicycle–motor vehicle accidents using a multinomial logit model. The model predicts the probability of four injury severity outcomes: fatal, incapacitating, non-incapacitating, and possible or no injury. The analysis is based on police-reported accident data between 1997 and 2002 from North Carolina, USA. The results show several factors which more than double the probability of a bicyclist suffering a fatal injury in an accident, all other things being kept constant. Notably, inclement weather, darkness with no streetlights, a.m. peak (06:00 a.m. to 09:59 a.m.), head-on collision, speeding-involved, vehicle speeds above 48.3 km/h (30 mph), truck involved, intoxicated driver, bicyclist age 55 or over, and intoxicated bicyclist. The largest effect is caused when estimated vehicle speed prior to impact is greater than 80.5 km/h (50 mph), where the probability of fatal injury increases more than 16-fold. Speed also shows a threshold effect at 32.2 km/h (20 mph), which supports the commonly used 30 km/h speed limit in residential neighborhoods. The results also imply that bicyclist fault is more closely correlated with greater bicyclist injury severity than driver fault. }
}
@article{Holdridge2005139,
title = {The crash severity impacts of fixed roadside objects },
journal = {Journal of Safety Research },
volume = {36},
number = {2},
pages = {139 - 147},
year = {2005},
note = {},
issn = {0022-4375},
doi = {http://dx.doi.org/10.1016/j.jsr.2004.12.005},
url = {http://www.sciencedirect.com/science/article/pii/S0022437505000186},
author = {Jason M. Holdridge and Venky N. Shankar and Gudmundur F. Ulfarsson},
keywords = {Injury severity},
keywords = {Injury prevention},
keywords = {Fixed-objects},
keywords = {Roadside hardware},
keywords = {Guardrails },
abstract = {Introduction: This study analyzes the in-service performance of roadside hardware on the entire urban State Route system in Washington State by developing multivariate statistical models of injury severity in fixed-object crashes using discrete outcome theory. The objective is to provide deeper insight into significant factors that affect crash severities involving fixed roadside objects, through improved statistical efficiency along with disaggregate and multivariate analysis. Method: The developed models are multivariate nested logit models of injury severity and they are estimated with statistical efficiency using the method of full information maximum likelihood. Results: The results show that leading ends of guardrails and bridge rails, along with large wooden poles (e.g. trees and utility poles) increase the probability of fatal injury. The face of guardrails is associated with a reduction in the probability of evident injury, and concrete barriers are shown to be associated with a higher probability of lower severities. Other variables included driver characteristics, which showed expected results, validating the model. For example, driving over the speed limit and driving under the influence of alcohol increase the probability of fatal accidents. Drivers that do not use seatbelts are associated with an increase in the probability of more severe injuries, even when an airbag is activated. Impact on industry: The presented models show the contribution of guardrail leading ends toward fatal injuries. It is therefore important to use well-designed leading ends and to upgrade badly performing leading ends on guardrails and bridges. The models also indicate the importance of protecting vehicles from crashes with rigid poles and tree stumps, as these are linked with greater severities and fatalities. }
}
@article{Shankar2003627,
title = {Modeling crashes involving pedestrians and motorized traffic },
journal = {Safety Science },
volume = {41},
number = {7},
pages = {627 - 640},
year = {2003},
note = {},
issn = {0925-7535},
doi = {http://dx.doi.org/10.1016/S0925-7535(02)00017-6},
url = {http://www.sciencedirect.com/science/article/pii/S0925753502000176},
author = {Venkataraman N. Shankar and Gudmundur F. Ulfarsson and Ram M. Pendyala and MaryLou B. Nebergall},
abstract = {This paper presents an empirical inquiry into the predictive modeling of crashes involving pedestrians and motorized traffic on roadways. Empirical models based on the negative binomial distribution and mixing distributions, such as the zero-inflated Poisson distribution, are presented and discussed in terms of their applicability to pedestrian crash phenomena. Key modeling issues relating to the presence of excess zeros as well as unobserved heterogeneity in pedestrian crash distributions are addressed. The empirical results show that zero-inflated count distributions, such as the zero-inflated Poisson, are promising methodologies for providing explanatory insights into the causality behind pedestrian-traffic crashes. }
}
@comment{{Neveen Eluru PAPERS}}
@article{FaghihImani201553,
title = {Analysing bicycle-sharing system user destination choice preferences: Chicago’s Divvy system },
journal = {Journal of Transport Geography },
volume = {44},
number = {0},
pages = {53 - 64},
year = {2015},
note = {},
issn = {0966-6923},
doi = {http://dx.doi.org/10.1016/j.jtrangeo.2015.03.005},
url = {http://www.sciencedirect.com/science/article/pii/S0966692315000459},
author = {Ahmadreza Faghih-Imani and Naveen Eluru},
keywords = {Bicycle sharing systems},
keywords = {Divvy Chicago},
keywords = {Destination choice},
keywords = {Location choice},
keywords = {Multinomial logit model},
keywords = {Bicycle infrastructure },
abstract = {Abstract In recent years, there has been increasing attention on bicycle-sharing systems (BSS) as a viable and sustainable mode of transportation for short trips. However, due to the relatively recent adoption of BSS, there is very little research exploring how people consider these systems within existing transportation options. Given recent \{BSS\} growth around the world, there is substantial interest in identifying contributing factors that encourage individuals to use these systems. The current study contributes to this growing literature by examining \{BSS\} behavior at the trip level to analyze bicyclists’ destination preferences. Specifically, we study the decision process involved in identifying destination locations after picking up a bicycle at a \{BSS\} station, using a random utility maximization approach in the form of a multinomial logit model (MNL). The quantitative frameworks developed have been estimated using 2013 data from the Chicago’s Divvy system. In our modeling effort, we distinguish between \{BSS\} users with annual membership and short-term customers with daily passes. The developed model should allow bicycle-sharing system operators to plan services more effectively by examining the impact of travel distance, land use, built environment, and access to public transportation infrastructure on users’ destination preferences. Using the estimated model, we generated utility profiles as a function of distance and various other attributes, allowing us to represent visually the trade-offs that individuals make in the decision process. To illustrate further the applicability of the proposed framework for planning purposes, destination station-choice probability prediction is undertaken. }
}
@article{FaghihImani2014306,
title = {How land-use and urban form impact bicycle flows: evidence from the bicycle-sharing system (BIXI) in Montreal },
journal = {Journal of Transport Geography },
volume = {41},
number = {0},
pages = {306 - 314},
year = {2014},
note = {},
issn = {0966-6923},
doi = {http://dx.doi.org/10.1016/j.jtrangeo.2014.01.013},
url = {http://www.sciencedirect.com/science/article/pii/S0966692314000234},
author = {Ahmadreza Faghih-Imani and Naveen Eluru and Ahmed M. El-Geneidy and Michael Rabbat and Usama Haq},
keywords = {Bicycle-sharing systems},
keywords = {\{BIXI\} Montreal},
keywords = {\{BIXI\} arrivals and departures},
keywords = {Linear mixed models},
keywords = {Bicycle infrastructure},
keywords = {Land use and built environment },
abstract = {Abstract Installed in 2009, \{BIXI\} is the first major public bicycle-sharing system in Montreal, Canada. The \{BIXI\} system has been a success, accounting for more than one million trips annually. This success has increased the interest in exploring the factors affecting bicycle-sharing flows and usage. Using data compiled as minute-by-minute readings of bicycle availability at all the stations of the \{BIXI\} system between April and August 2012, this study contributes to the literature on bicycle-sharing. We examine the influence of meteorological data, temporal characteristics, bicycle infrastructure, land use and built environment attributes on arrival and departure flows at the station level using a multilevel approach to statistical modeling, which could easily be applied to other regions. The findings allow us to identify factors contributing to increased usage of bicycle-sharing in Montreal and to provide recommendations pertaining to station size and location decisions. The developed methodology and findings can be of benefit to city planners and engineers who are designing or modifying bicycle-sharing systems with the goal of maximizing usage and availability. }
}
@article{Eluru20131,
title = {Evaluating alternate discrete choice frameworks for modeling ordinal discrete variables },
journal = {Accident Analysis & Prevention },
volume = {55},
number = {0},
pages = {1 - 11},
year = {2013},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2013.02.012},
url = {http://www.sciencedirect.com/science/article/pii/S000145751300050X},
author = {Naveen Eluru},
keywords = {Ordered and unordered discrete choice models for injury severity},
keywords = {Ordinal discrete variables},
keywords = {Generalized ordered logit},
keywords = {Comparison },
abstract = {There is considerable debate on the appropriate discrete choice framework for examining injury severity. Researchers in the safety field have employed ordered and unordered frameworks for examining the various factors influencing injury severity. The objective of the current study is to investigate the performance of the ordered and unordered response frameworks at a fundamental level. Towards this end, we undertake a comparison of the alternative frameworks by estimating ordered and unordered response models using data generated through ordered, unordered data and a combination of ordered and unordered data generation processes. We also examine the influence of aggregate sample shares on the appropriateness of the modeling framework. Rather than be limited by the aggregate sample shares in an empirical dataset, simulation allows us to explore the influence of a broad spectrum of sample shares on the performance of ordered and unordered frameworks. We also extend the data generation process based analysis to under reported data and compare the performance of the ordered and unordered response frameworks. Finally, based on these simulation exercises, we provide a discussion of the merits of the different approaches. The results clearly highlight the emergence of the generalized ordered logit model as a true equivalent ordered response model to the multinomial logit model for ordinal discrete variables. }
}
@article{Sobhani2013154,
title = {A latent segmentation based multiple discrete continuous extreme value model },
journal = {Transportation Research Part B: Methodological },
volume = {58},
number = {0},
pages = {154 - 169},
year = {2013},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/j.trb.2013.07.009},
url = {http://www.sciencedirect.com/science/article/pii/S0191261513001240},
author = {Anae Sobhani and Naveen Eluru and Ahmadreza Faghih-Imani},
keywords = {Multiple discrete continuous models},
keywords = {Latent segmentation approaches},
keywords = {Daily vehicle type and use decisions},
keywords = {Activity type},
keywords = {Accompaniment type},
keywords = {Mileage },
abstract = {Abstract We examine an alternative method to incorporate potential presence of population heterogeneity within the Multiple Discrete Continuous Extreme Value (MDCEV) model structure. Towards this end, an endogenous segmentation approach is proposed that allocates decision makers probabilistically to various segments as a function of exogenous variables. Within each endogenously determined segment, a segment specific \{MDCEV\} model is estimated. This approach provides insights on the various population segments present while evaluating distinct choice regimes for each of these segments. The segmentation approach addresses two concerns: (1) ensures that the parameters are estimated employing the full sample for each segment while using all the population records for model estimation, and (2) provides valuable insights on how the exogenous variables affect segmentation. An Expectation–Maximization algorithm is proposed to address the challenges of estimating the resulting endogenous segmentation based econometric model. A prediction procedure to employ the estimated latent \{MDCEV\} models for forecasting is also developed. The proposed model is estimated using data from 2009 National Household Travel Survey (NHTS) for the New York region. The results of the model estimates and prediction exercises illustrate the benefits of employing an endogenous segmentation based \{MDCEV\} model. The challenges associated with the estimation of latent \{MDCEV\} models are also documented. }
}
@article{Yasmin20131020,
title = {Examining the Continuum of Injury Severity: Pooling the \{GES\} and \{FARS\} Datasets },
journal = {Procedia - Social and Behavioral Sciences },
volume = {104},
number = {0},
pages = {1020 - 1029},
year = {2013},
note = {2nd Conference of Transportation Research Group of India (2nd CTRG) },
issn = {1877-0428},
doi = {http://dx.doi.org/10.1016/j.sbspro.2013.11.197},
url = {http://www.sciencedirect.com/science/article/pii/S1877042813045886},
author = {Shamsunnahar Yasmin and Abdul R. Pinjari and Naveen Eluru},
keywords = {Data Pooling},
keywords = {Fatality risk},
keywords = {Generalized ordered logit},
keywords = {\{FARS\}},
keywords = {\{GES\} },
abstract = {Abstract Given the import of the consequences of motor vehicle crashes, transportation safety researchers examined the influence of exogenous variables on vehicle occupant injury severity. Our study focuses on identifying the associated risk factors of driver fatalities while recognizing that fatality is not a single state but rather is made up of multiple discrete states from dying instantly to dying within the thirty days of crash by using the data from Fatality Analysis Reporting System (FARS). The research also simultaneously examines the whole spectrum of injury severity on an eleven point ordinal severity scale - no injury to fatality characterized as instant death by using a pooled dataset from \{FARS\} and General Estimates System (GES) dataset. The data pooling exercise is done to replace the “less informative” fatal crashes in the \{GES\} databases with the more detailed fatal crashes from \{FARS\} database. The data for the current study is sourced from the \{FARS\} and \{GES\} databases for the year 2010. The generalized ordered logit approach is considered for the empirical analyses. The important control variables that affect the both the early fatality risk and the injury severity outcome of the drivers include: driving under the influence of alcohol, medium or higher speed limits and increase in vehicle age. }
}
@article{Yasmin2013506,
title = {Evaluating alternate discrete outcome frameworks for modeling crash injury severity },
journal = {Accident Analysis & Prevention },
volume = {59},
number = {0},
pages = {506 - 521},
year = {2013},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2013.06.040},
url = {http://www.sciencedirect.com/science/article/pii/S0001457513002716},
author = {Shamsunnahar Yasmin and Naveen Eluru},
keywords = {Comparison of discrete outcome models},
keywords = {\{MGOL\}},
keywords = {\{MMNL\}},
keywords = {Underreporting},
keywords = {Validation },
abstract = {Abstract This paper focuses on the relevance of alternate discrete outcome frameworks for modeling driver injury severity. The study empirically compares the ordered response and unordered response models in the context of driver injury severity in traffic crashes. The alternative modeling approaches considered for the comparison exercise include: for the ordered response framework-ordered logit (OL), generalized ordered logit (GOL), mixed generalized ordered logit (MGOL) and for the unordered response framework-multinomial logit (MNL), nested logit (NL), ordered generalized extreme value logit (OGEV) and mixed multinomial logit (MMNL) model. A host of comparison metrics are computed to evaluate the performance of these alternative models. The study provides a comprehensive comparison exercise of the performance of ordered and unordered response models for examining the impact of exogenous factors on driver injury severity. The research also explores the effect of potential underreporting on alternative frameworks by artificially creating an underreported data sample from the driver injury severity sample. The empirical analysis is based on the 2010 General Estimates System (GES) data base—a nationally representative sample of road crashes collected and compiled from about 60 jurisdictions across the United States. The performance of the alternative frameworks are examined in the context of model estimation and validation (at the aggregate and disaggregate level). Further, the performance of the model frameworks in the presence of underreporting is explored, with and without corrections to the estimates. The results from these extensive analyses point toward the emergence of the \{GOL\} framework (MGOL) as a strong competitor to the \{MMNL\} model in modeling driver injury severity. }
}
@article{Eluru2013125,
title = {Modeling vehicle operating speed on urban roads in Montreal: A panel mixed ordered probit fractional split model },
journal = {Accident Analysis & Prevention },
volume = {59},
number = {0},
pages = {125 - 134},
year = {2013},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2013.05.016},
url = {http://www.sciencedirect.com/science/article/pii/S0001457513002157},
author = {Naveen Eluru and Vincent Chakour and Morgan Chamberlain and Luis F. Miranda-Moreno},
keywords = {Fractional split models},
keywords = {Mixed ordered response fractional split models},
keywords = {Vehicle operating speed},
keywords = {Montreal },
abstract = {Abstract Vehicle operating speed measured on roadways is a critical component for a host of analysis in the transportation field including transportation safety, traffic flow modeling, roadway geometric design, vehicle emissions modeling, and road user route decisions. The current research effort contributes to the literature on examining vehicle speed on urban roads methodologically and substantively. In terms of methodology, we formulate a new econometric model framework for examining speed profiles. The proposed model is an ordered response formulation of a fractional split model. The ordered nature of the speed variable allows us to propose an ordered variant of the fractional split model in the literature. The proposed formulation allows us to model the proportion of vehicles traveling in each speed interval for the entire segment of roadway. We extend the model to allow the influence of exogenous variables to vary across the population. Further, we develop a panel mixed version of the fractional split model to account for the influence of site-specific unobserved effects. The paper contributes substantively by estimating the proposed model using a unique dataset from Montreal consisting of weekly speed data (collected in hourly intervals) for about 50 local roads and 70 arterial roads. We estimate separate models for local roads and arterial roads. The model estimation exercise considers a whole host of variables including geometric design attributes, roadway attributes, traffic characteristics and environmental factors. The model results highlight the role of various street characteristics including number of lanes, presence of parking, presence of sidewalks, vertical grade, and bicycle route on vehicle speed proportions. The results also highlight the presence of site-specific unobserved effects influencing the speed distribution. The parameters from the modeling exercise are validated using a hold-out sample not considered for model estimation. The results indicate that the proposed panel mixed ordered probit fractional split model offers promise for modeling such proportional ordinal variables. }
}
@article{Chakour2013875,
title = {Examining the Influence of Urban form and Land Use on Bus Ridership in Montreal },
journal = {Procedia - Social and Behavioral Sciences },
volume = {104},
number = {0},
pages = {875 - 884},
year = {2013},
note = {2nd Conference of Transportation Research Group of India (2nd CTRG) },
issn = {1877-0428},
doi = {http://dx.doi.org/10.1016/j.sbspro.2013.11.182},
url = {http://www.sciencedirect.com/science/article/pii/S1877042813045734},
author = {Vincent Chakour and Naveen Eluru},
keywords = {Bus ridership},
keywords = {land use},
keywords = {boarding},
keywords = {alighting},
keywords = {ordered regression},
keywords = {composite marginal likelihood },
abstract = {Abstract The prevalence of sub urban life in North American cities in the recent decades has resulted in increased private vehicle usage while reducing public transportation system usage. An oft suggested alternative to reduce the negative externalities of the personal vehicle use is the development of an efficient public transportation system that provides equitable service and accessibility to the population as well as contributes to the reduction of air pollution and \{GHG\} emissions. The emphasis of this study is on a systems perspective where transit ridership is studied from the perspective of the transit provider, with the objective of quantifying the influence of transit system operational attributes, transportation system infrastructure attributes and built environment attributes on the disaggregate stop level boardings and alightings for the bus network in the Montreal region. A Composite Marginal Likelihood (CML) based ordered response probit (ORP) model that simultaneously allows to incorporate the influence of exogenous variables along and potential correlations between boardings and alightings a r multiple time periods examined is employed Our results illustrate that headway impacts ridership negatively, while the presence of public transportation around the stop has a positive and significant effect. Moreover, parks, commerces, and residential area, amongst others, impact boardings and alightings at different bus stops. The results a provide transit agencies a mechanism to study the influence of transit accessibility, transit connectivity, transit schedule alterations (to increase/reduce headway), and land use pattern changes on ridership. }
}
@article{Sider2013230,
title = {Land-use and socio-economics as determinants of traffic emissions and individual exposure to air pollution },
journal = {Journal of Transport Geography },
volume = {33},
number = {0},
pages = {230 - 239},
year = {2013},
note = {},
issn = {0966-6923},
doi = {http://dx.doi.org/10.1016/j.jtrangeo.2013.08.006},
url = {http://www.sciencedirect.com/science/article/pii/S0966692313001555},
author = {Timothy Sider and Ahsan Alam and Mohamad Zukari and Hussam Dugum and Nathan Goldstein and Naveen Eluru and Marianne Hatzopoulou},
keywords = {Land-use and emissions},
keywords = {Emission modeling},
keywords = {Air pollution exposure},
keywords = {\{MOVES\}},
keywords = {Individual emissions },
abstract = {Abstract This paper presents a modeling framework developed for the City of Montreal, Canada, and is intended to quantify two indicators that can explain the spatial distribution of traffic-related air pollution at a metropolitan level. The indicators are estimated at the level of the traffic analysis zone (TAZ) and include: (1) the average level of emissions generated per individual and (2) the level of emissions occurring in a zone as a proxy for air pollution exposure. A regional traffic assignment model is extended with capabilities for emission modeling at an individual trip level while taking into account vehicle (type and age) and trip attributes (road type, speed, and volume). We observe that individuals who generate higher emissions from travel tend to reside in areas with lower exposure to traffic emissions while individuals associated with low levels of travel emissions (e.g. travel smaller distances, conduct less trips, and use alternative modes) reside in areas with high levels of traffic pollution. A regression analysis of the two indicators against a set of land-use and socio-economic variables shows that generated emissions per individual are positively associated with car ownership and larger vehicles, while being negatively associated with ownership of newer vehicles, and location in dense and walkable neighborhoods with high levels of commercial land-use. Meanwhile, exposure to emissions is positively associated with dense and walkable neighborhoods and negatively associated with car ownership and larger vehicles. These findings indicate major inequities in the generation of and exposure to traffic-related air pollution. }
}
@article{Sikder2013640,
title = {Spatial Transferability of Tour-based Time-of-day Choice Models: An Empirical Assessment },
journal = {Procedia - Social and Behavioral Sciences },
volume = {104},
number = {0},
pages = {640 - 649},
year = {2013},
note = {2nd Conference of Transportation Research Group of India (2nd CTRG) },
issn = {1877-0428},
doi = {http://dx.doi.org/10.1016/j.sbspro.2013.11.158},
url = {http://www.sciencedirect.com/science/article/pii/S1877042813045497},
author = {Sujan Sikder and Bertho Augustin and Abdul Rawoof Pinjari and Naveen Eluru},
keywords = {Time-of-day choice},
keywords = {transferability},
keywords = {multinomial logit model},
keywords = {pooling data },
abstract = {Abstract This paper presents an empirical assessment of the spatial transferability of tour-based time-of-day choice models across different counties in the San Francisco Bay Area of California. Model transferability was assessed using two different approaches: (1) estimation-based approach, and (2) application-based approach. The former approach allows the analyst to test which specific coefficients in the model are transferable and which are not, while the latter approach tests the transferability of a model as a whole. In addition, the hypothesis that pooling data from different geographical contexts helps in estimating better transferable models than those developed from a single context was tested. The estimation-based approach yields encouraging results in favour of model transferability, with a majority of the coefficients in a pooled model found to be transferrable. Pooling data from different geographical contexts appears to help in developing better transferable models but careful attention is needed in selecting the geographical contexts to pool the data from. }
}
@article{Eluru2012119,
title = {A latent class modeling approach for identifying vehicle driver injury severity factors at highway-railway crossings },
journal = {Accident Analysis & Prevention },
volume = {47},
number = {0},
pages = {119 - 127},
year = {2012},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2012.01.027},
url = {http://www.sciencedirect.com/science/article/pii/S0001457512000474},
author = {Naveen Eluru and Morteza Bagheri and Luis F. Miranda-Moreno and Liping Fu},
keywords = {Collision consequence},
keywords = {Highway-railway crossing},
keywords = {Occupant injury severity},
keywords = {Latent segmentation based ordered response model },
abstract = {In this paper, we aim to identify the different factors that influence injury severity of highway vehicle occupants, in particular drivers, involved in a vehicle-train collision at highway-railway grade crossings. The commonly used approach to modeling vehicle occupant injury severity is the traditional ordered response model that assumes the effect of various exogenous factors on injury severity to be constant across all accidents. The current research effort attempts to address this issue by applying an innovative latent segmentation based ordered logit model to evaluate the effects of various factors on the injury severity of vehicle drivers. In this model, the highway-railway crossings are assigned probabilistically to different segments based on their attributes with a separate injury severity component for each segment. The validity and strength of the formulated collision consequence model is tested using the \{US\} Federal Railroad Administration database which includes inventory data of all the railroad crossings in the \{US\} and collision data at these highway railway crossings from 1997 to 2006. The model estimation results clearly highlight the existence of risk segmentation within the affected grade crossing population by the presence of active warning devices, presence of permanent structure near the crossing and roadway type. The key factors influencing injury severity include driver age, time of the accident, presence of snow and/or rain, vehicle role in the crash and motorist action prior to the crash. }
}
@article{Sener20101,
title = {On Jointly Analyzing the Physical Activity Participation Levels of Individuals in a Family Unit Using a Multivariate Copula Framework },
journal = {Journal of Choice Modelling },
volume = {3},
number = {3},
pages = {1 - 38},
year = {2010},
note = {},
issn = {1755-5345},
doi = {http://dx.doi.org/10.1016/S1755-5345(13)70012-5},
url = {http://www.sciencedirect.com/science/article/pii/S1755534513700125},
author = {Ipek N. Sener and Naveen Eluru and Chandra R. Bhat},
keywords = {Copulas},
keywords = {physical activity},
keywords = {family and public health},
keywords = {social dependency},
keywords = {data clustering},
keywords = {activity-based travel analysis },
abstract = {Abstract The current paper focuses on analyzing and modeling the physical activity participation levels (in terms of the number of daily “bouts” or “episodes” of physical activity during a weekend day) of all members of a family jointly. Essentially, we consider a family as a “cluster” of individuals whose physical activity propensities may be affected by common household attributes (such as household income and household structure) as well as unobserved family-related factors (such as family life-style and health consciousness, and residential location-related factors). The proposed copula-based clustered ordered-response model structure allows the testing of various dependency forms among the physical activity propensities of individuals of the same household (generated due to the unobserved family-related factors), including non-linear and asymmetric dependency forms. The proposed model system is applied to study physical activity participations of individuals, using data drawn from the 2000 San Francisco Bay Area Household Travel Survey (BATS). A number of individual factors, physical environment factors, and social environment factors are considered in the empirical analysis. The results indicate that reduced vehicle ownership and increased bicycle ownership are important positive determinants of weekend physical activity participation levels, though these results should be tempered by the possibility that individuals who are predisposed to physical activity may choose to own fewer motorized vehicles and more bicycles in the first place. Our results also suggest that policy interventions aimed at increasing children's physical activity levels could potentially benefit from targeting entire family units rather than targeting only children. Finally, the results indicate strong and asymmetric dependence among the unobserved physical activity determinants of family members. In particular, the results show that unobserved factors (such as residence location-related constraints and family lifestyle preferences) result in individuals in a family having uniformly low physical activity, but there is less clustering of this kind at the high end of the physical activity propensity spectrum. }
}
@article{Eluru20081033,
title = {A mixed generalized ordered response model for examining pedestrian and bicyclist injury severity level in traffic crashes },
journal = {Accident Analysis & Prevention },
volume = {40},
number = {3},
pages = {1033 - 1054},
year = {2008},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2007.11.010},
url = {http://www.sciencedirect.com/science/article/pii/S0001457507002072},
author = {Naveen Eluru and Chandra R. Bhat and David A. Hensher},
keywords = {Injury severity},
keywords = {Ordered response model},
keywords = {Pedestrian safety},
keywords = {Bicyclist safety},
keywords = {Non-motorized travel },
abstract = {This paper proposes an econometric structure for injury severity analysis at the level of individual accidents that recognizes the ordinal nature of the categories in which injury severity are recorded, while also allowing flexibility in capturing the effects of explanatory variables on each ordinal category and allowing heterogeneity in the effects of contributing factors due to the moderating influence of unobserved factors. The model developed here, referred to as the mixed generalized ordered response logit (MGORL) model, generalizes the standard ordered response models used in the extant literature for injury severity analysis. To our knowledge, this is the first such formulation to be proposed and applied in the econometric literature in general, and in the safety analysis literature in particular. The \{MGORL\} model is applied to examine non-motorist injury severity in accidents in the USA, using the 2004 General Estimates System (GES) database. The empirical findings emphasize the inconsistent results obtained from the standard ordered response model. An important policy result from our analysis is that the general pattern and relative magnitude of elasticity effects of injury severity determinants are similar for pedestrians and bicyclists. The analysis also suggests that the most important variables influencing non-motorist injury severity are the age of the individual (the elderly are more injury-prone), the speed limit on the roadway (higher speed limits lead to higher injury severity levels), location of crashes (those at signalized intersections are less severe than those elsewhere), and time-of-day (darker periods lead to higher injury severity). }
}
@article{Bhat2010903,
title = {A flexible spatially dependent discrete choice model: Formulation and application to teenagers’ weekday recreational activity participation },
journal = {Transportation Research Part B: Methodological },
volume = {44},
number = {8–9},
pages = {903 - 921},
year = {2010},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/j.trb.2010.02.003},
url = {http://www.sciencedirect.com/science/article/pii/S0191261510000184},
author = {Chandra R. Bhat and Ipek N. Sener and Naveen Eluru},
keywords = {Spatial econometrics},
keywords = {Copula},
keywords = {Composite marginal likelihood (CML) inference approach},
keywords = {Children’s activity},
keywords = {Public health},
keywords = {Physical activity },
abstract = {This study proposes a simple and practical Composite Marginal Likelihood (CML) inference approach to estimate ordered-response discrete choice models with flexible copula-based spatial dependence structures across observational units. The approach is applicable to data sets of any size, provides standard error estimates for all parameters, and does not require any simulation machinery. The combined copula–CML approach proposed here should be appealing for general multivariate modeling contexts because it is simple and flexible, and is easy to implement The ability of the \{CML\} approach to recover the parameters of a spatially ordered process is evaluated using a simulation study, which clearly points to the effectiveness of the approach. In addition, the combined copula–CML approach is applied to study the daily episode frequency of teenagers’ physically active and physically inactive recreational activity participation, a subject of considerable interest in the transportation, sociology, and adolescence development fields. The data for the analysis are drawn from the 2000 San Francisco Bay Area Survey. The results highlight the value of the copula approach that separates the univariate marginal distribution form from the multivariate dependence structure, as well as underscore the need to consider spatial effects in recreational activity participation. The variable effects indicate that parents’ physical activity participation constitutes the most important factor influencing teenagers’ physical activity participation levels. Thus, an effective way to increase active recreation among teenagers may be to direct physical activity benefit-related information and education campaigns toward parents, perhaps at special physical education sessions at the schools of teenagers. }
}
@article{Ferdous2010922,
title = {A multivariate ordered-response model system for adults’ weekday activity episode generation by activity purpose and social context },
journal = {Transportation Research Part B: Methodological },
volume = {44},
number = {8–9},
pages = {922 - 943},
year = {2010},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/j.trb.2010.02.002},
url = {http://www.sciencedirect.com/science/article/pii/S0191261510000172},
author = {Nazneen Ferdous and Naveen Eluru and Chandra R. Bhat and Italo Meloni},
keywords = {Composite marginal likelihood (CML) approach},
keywords = {Social interactions},
keywords = {Activity-based modeling},
keywords = {Multivariate ordered probit model},
keywords = {American Time Use Survey (ATUS) },
abstract = {This paper proposes a multivariate ordered-response system framework to model the interactions in non-work activity episode decisions across household and non-household members at the level of activity generation. Such interactions in activity decisions across household and non-household members are important to consider for accurate activity-travel pattern modeling and policy evaluation. The econometric challenge in estimating a multivariate ordered-response system with a large number of categories is that traditional classical and Bayesian simulation techniques become saddled with convergence problems and imprecision in estimates, and they are also extremely cumbersome if not impractical to implement. We address this estimation problem by resorting to the technique of composite marginal likelihood (CML), an emerging inference approach in the statistics field that is based on the classical frequentist approach, is very simple to estimate, is easy to implement regardless of the number of count outcomes to be modeled jointly, and requires no simulation machinery whatsoever. The empirical analysis in the paper uses data drawn from the 2007 American Time Use Survey (ATUS) and provides important insights into the determinants of adults’ weekday activity episode generation behavior. The results underscore the substantial linkages in the activity episode generation of adults based on activity purpose and accompaniment type. The extent of this linkage varies by individual demographics, household demographics, day of the week, and season of the year. The results also highlight the flexibility of the \{CML\} approach to specify and estimate behaviorally rich structures to analyze inter-individual interactions in activity episode generation. }
}
@article{Bhat20091,
title = {The impact of demographics, built environment attributes, vehicle characteristics, and gasoline prices on household vehicle holdings and use },
journal = {Transportation Research Part B: Methodological },
volume = {43},
number = {1},
pages = {1 - 18},
year = {2009},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/j.trb.2008.06.009},
url = {http://www.sciencedirect.com/science/article/pii/S0191261508000775},
author = {Chandra R. Bhat and Sudeshna Sen and Naveen Eluru},
keywords = {\{MDCEV\} model},
keywords = {Gasoline prices},
keywords = {Built environment},
keywords = {Household vehicle holdings and use},
keywords = {Vehicle make/model choice },
abstract = {In this paper, we formulate and estimate a nested model structure that includes a multiple discrete-continuous extreme value (MDCEV) component to analyze the choice of vehicle type/vintage and usage in the upper level and a multinomial logit (MNL) component to analyze the choice of vehicle make/model in the lower nest. Data for the analysis are drawn from the 2000 San Francisco Bay Area Travel Survey. The model results indicate the important effects of household demographics, household location characteristics, built environment attributes, household head characteristics, and vehicle attributes on household vehicle holdings and use. The model developed in the paper is applied to predict the impact of land-use and fuel cost changes on vehicle holdings and usage of the households. Such predictions can inform the design of proactive land-use, economic, and transportation policies to influence household vehicle holdings and usage in a way that reduces the negative impacts of automobile dependency such as traffic congestion, fuel consumption and air pollution. }
}
@article{Eluru20071037,
title = {A joint econometric analysis of seat belt use and crash-related injury severity },
journal = {Accident Analysis & Prevention },
volume = {39},
number = {5},
pages = {1037 - 1049},
year = {2007},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2007.02.001},
url = {http://www.sciencedirect.com/science/article/pii/S0001457507000206},
author = {Naveen Eluru and Chandra R. Bhat},
keywords = {Seat belt use},
keywords = {Crash injury severity},
keywords = {Random coefficients},
keywords = {Selective recruitment},
keywords = {Discrete choice models with endogeneity },
abstract = {This paper formulates a comprehensive econometric structure that recognizes two important issues in crash-related injury severity analysis. First, the impact of a factor on injury severity may be moderated by various observed and unobserved variables specific to an individual or to a crash. Second, seat belt use is likely to be endogenous to injury severity. That is, it is possible that intrinsically unsafe drivers do not wear seat belts and are the ones likely to be involved in high injury severity crashes because of their unsafe driving habits. The preceding issues are considered in the current research effort through the development of a comprehensive model of seat belt use and injury severity that takes the form of a joint correlated random coefficients binary-ordered response system. To our knowledge, this is the first instance of such a model formulation and application not only in the safety analysis literature, but in the econometrics literature in general. The empirical analysis is based on the 2003 General Estimates System (GES) data base. Several types of variables are considered to explain seat belt use and injury severity levels, including driver characteristics, vehicle characteristics, roadway design attributes, environmental factors, and crash characteristics. The results, in addition to confirming the effects of various explanatory variables, also highlight the importance of (a) considering the moderating effects of unobserved individual/crash-related factors on the determinants of injury severity and (b) seat belt use endogeneity. From a policy standpoint, the results suggest that seat belt non-users, when apprehended in the act, should perhaps be subjected to both a fine (to increase the chances that they wear seat belts) as well as mandatory enrollment in a defensive driving course (to attempt to change their aggressive driving behaviors). }
}
@article{Paleti20101839,
title = {Examining the influence of aggressive driving behavior on driver injury severity in traffic crashes },
journal = {Accident Analysis & Prevention },
volume = {42},
number = {6},
pages = {1839 - 1854},
year = {2010},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2010.05.005},
url = {http://www.sciencedirect.com/science/article/pii/S0001457510001417},
author = {Rajesh Paleti and Naveen Eluru and Chandra R. Bhat},
keywords = {Crash injury severity},
keywords = {Graduated licensing programs (GDL)},
keywords = {Teenage drivers},
keywords = {Driving aggressiveness},
keywords = {Risk taking},
keywords = {Parenting },
abstract = {In this paper, we capture the moderating effect of aggressive driving behavior while assessing the influence of a comprehensive set of variables on injury severity. In doing so, we are able to account for the indirect effects of variables on injury severity through their influence on aggressive driving behavior, as well as the direct effect of variables on injury severity. The methodology used in the paper to accommodate the moderating effect of aggressive driving behavior takes the form of two models – one for aggressive driving and another for injury severity. These are appropriately linked to obtain the indirect and direct effects of variables. The data for estimation is obtained from the National Motor Vehicle Crash Causation Study (NMVCCS). From an empirical standpoint, we consider a fine age categorization until 20 years of age when examining age effects on aggressive driving behavior and injury severity. There are several important results from the empirical analysis undertaken in the current paper based on post-crash data collection on aggressive behavior participation just prior to the crash and injury severity sustained in a crash. Young drivers (especially novice drivers between 16 and 17 years of age), drivers who are not wearing seat belt, under the influence of alcohol, not having a valid license, and driving a pick-up are found to be most likely to behave aggressively. Situational, vehicle, and roadway factors such as young drivers traveling with young passengers, young drivers driving an \{SUV\} or a pick-up truck, driving during the morning rush hour, and driving on roads with high speed limits are also found to trigger aggressive driving behavior. In terms of vehicle occupants, the safest situation from a driver injury standpoint is when there are two or more passengers in the vehicle, at least one of whom is above the age of 20 years. These and many other results are discussed, along with implications of the result for graduated driving licensing (GDL) programs. }
}
@comment{{Richard Tay PAPERS}}
@article{Li20148,
title = {Improving drivers’ knowledge of road rules using digital games },
journal = {Accident Analysis & Prevention },
volume = {65},
number = {0},
pages = {8 - 10},
year = {2014},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2013.12.003},
url = {http://www.sciencedirect.com/science/article/pii/S000145751300482X},
author = {Qing Li and Richard Tay},
keywords = {Road safety},
keywords = {Digital games},
keywords = {Road rules},
keywords = {Driver education },
abstract = {Abstract Although a proficient knowledge of the road rules is important to safe driving, many drivers do not retain the knowledge acquired after they have obtained their licenses. Hence, more innovative and appealing methods are needed to improve drivers’ knowledge of the road rules. This study examines the effect of game based learning on drivers’ knowledge acquisition and retention. We find that playing an entertaining game that is designed to impart knowledge of the road rules not only improves players’ knowledge but also helps them retain such knowledge. Hence, learning by gaming appears to be a promising learning approach for driver education. }
}
@article{Yasmin2014120,
title = {Examining driver injury severity in two vehicle crashes – A copula based approach },
journal = {Accident Analysis & Prevention },
volume = {66},
number = {0},
pages = {120 - 135},
year = {2014},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2014.01.018},
url = {http://www.sciencedirect.com/science/article/pii/S0001457514000220},
author = {Shamsunnahar Yasmin and Naveen Eluru and Abdul R. Pinjari and Richard Tay},
keywords = {Injury severity profiles},
keywords = {Copula methods},
keywords = {Joint multinomial logit and ordered logit model},
keywords = {Two vehicle crashes },
abstract = {Abstract A most commonly identified exogenous factor that significantly affects traffic crash injury severity sustained is the collision type variable. Most studies consider collision type only as an explanatory variable in modeling injury. However, it is possible that each collision type has a fundamentally distinct effect on injury severity sustained in the crash. In this paper, we examine the hypothesis that collision type fundamentally alters the injury severity pattern under consideration. Toward this end, we propose a joint modeling framework to study collision type and injury severity sustained as two dimensions of the severity process. We employ a copula based joint framework that ties the collision type (represented as a multinomial logit model) and injury severity (represented as an ordered logit model) through a closed form flexible dependency structure to study the injury severity process. The proposed approach also accommodates the potential heterogeneity (across drivers) in the dependency structure. Further, the study incorporates collision type as a vehicle-level, as opposed to a crash-level variable as hitherto assumed in earlier research, while also examining the impact of a comprehensive set of exogenous factors on driver injury severity. The proposed modeling system is estimated using collision data from the province of Victoria, Australia for the years 2006 through 2010. }
}
@article{Yasmin201423,
title = {A latent segmentation based generalized ordered logit model to examine factors influencing driver injury severity },
journal = {Analytic Methods in Accident Research },
volume = {1},
number = {0},
pages = {23 - 38},
year = {2014},
note = {},
issn = {2213-6657},
doi = {http://dx.doi.org/10.1016/j.amar.2013.10.002},
url = {http://www.sciencedirect.com/science/article/pii/S2213665713000055},
author = {Shamsunnahar Yasmin and Naveen Eluru and Chandra R. Bhat and Richard Tay},
keywords = {Latent segmentation},
keywords = {Generalized ordered logit},
keywords = {Driver injury severity},
keywords = {Crash characteristics},
keywords = {Elasticities },
abstract = {Abstract This paper formulates and estimates an econometric model, referred to as the latent segmentation based generalized ordered logit (LSGOL) model, for examining driver injury severity. The proposed model probabilistically allocates drivers (involved in a crash) into different injury severity segments based on crash characteristics to recognize that the impacts of exogenous variables on driver injury severity level can vary across drivers based on both observed and unobserved crash characteristics. The proposed model is estimated using Victorian Crash Database from Australia for the years 2006 through 2010. The model estimation incorporates the influence of a comprehensive set of exogenous variables grouped into six broad categories: crash characteristics, driver characteristics, vehicle characteristics, roadway design attributes, environmental factors and situational factors. The results clearly highlight the need for segmentation based on crash characteristics. The crash characteristics that affect the allocation of drivers into segments include: collision object, trajectory of vehicle's motion and manner of collision. Further, the key factors resulting in severe driver injury severity are driver age 65 and above, driver ejection, not wearing seat belts and collision in a high speed zone. The factors reducing driver injury severity include the presence of pedestrian control, presence of roundabout, driving a panel van, unpaved road condition and the presence of passengers. }
}
@article{Tay2011955,
title = {Should traffic enforcement be unpredictable? The case of red light cameras in Edmonton },
journal = {Accident Analysis & Prevention },
volume = {43},
number = {3},
pages = {955 - 961},
year = {2011},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2010.11.022},
url = {http://www.sciencedirect.com/science/article/pii/S0001457510003660},
author = {Richard Tay and Alex de Barros},
keywords = {Optimal Deployment Strategy},
keywords = {Red light cameras},
keywords = {Rotation scheme},
keywords = {Red Light Violations },
abstract = {Red light cameras are installed in many jurisdictions around the world to improve road safety by discouraging red light running behaviour at signalized intersections. In many jurisdictions, a smaller number of cameras are rotated among a larger number of locations to increase the effectiveness of the red light camera programs. This study outlines some arguments for deciding the best deployment strategy that can be used to rotate these cameras, focusing on the deterrent effects of enforcement and punishment on driver behaviour. A simple on-road experiment is then conducted to determine the effectiveness of three different rotation schemes. Our results suggest that not moving the cameras and keeping enforcement predictable yields a lower average violation rate than moving the cameras around and making enforcement uncertain. }
}
@article{Anowar201393,
title = {Comparison of crashes during public holidays and regular weekends },
journal = {Accident Analysis & Prevention },
volume = {51},
number = {0},
pages = {93 - 97},
year = {2013},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2012.10.021},
url = {http://www.sciencedirect.com/science/article/pii/S0001457512003776},
author = {Sabreena Anowar and Shamsunnahar Yasmin and Richard Tay},
keywords = {Public holidays},
keywords = {Logistic regression},
keywords = {Speeding},
keywords = {Drink-driving},
keywords = {Seatbelt},
keywords = {Enforcement},
keywords = {Publicity campaigns },
abstract = {Traffic collisions and fatalities during the holiday festive periods are apparently on the rise in Alberta, Canada, despite the enhanced enforcement and publicity campaigns conducted during these periods. Using data from 2004 to 2008, this research identifies the factors that delineate between crashes that occur during public holidays and those occurring during normal weekends. We find that fatal and injury crashes are over-represented during holidays. Amongst the three risky behaviors targeted in the holiday blitzes (driver intoxication, unsafe speeding and restraint use), non-use of restraint is more prevalent whereas driver intoxication and unsafe speeding are less prevalent during holidays. The mixed results obtained suggest that it may be time to consider a more balanced approach to the enhanced enforcement and publicity campaigns. }
}
@article{Rifaat201244,
title = {Severity of motorcycle crashes in Calgary },
journal = {Accident Analysis & Prevention },
volume = {49},
number = {0},
pages = {44 - 49},
year = {2012},
note = {\{PTW\} + Cognitive impairment and Driving Safety },
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2011.02.025},
url = {http://www.sciencedirect.com/science/article/pii/S0001457511000467},
author = {Shakil Mohammad Rifaat and Richard Tay and Alexandre de Barros},
keywords = {Motorcycles},
keywords = {Crash severity},
keywords = {Logit models },
abstract = {Motorcycle riders would be more vulnerable in the event of a crash because of their lack of protection which would often result in them suffering more severe injuries than car drivers. This paper estimated three crash severity models to identify factors that contributed to increasing the severity of motorcycle involved crashes in the Canadian City of Calgary. We found that results from the ordered logit model, heterogeneous choice model and partially constrained generalized ordered logit model produced estimates that were very similar which attested to their robustness. Injury severity tended to increase in neighborhoods with loops and lollipops types of streets or involved right-angle and left-turn-across-path crashes, a truck, unsafe speed or alcohol use but tended to decrease if the crash occurred in parking lots or during winter, involved a van or male rider, or a rider following-too-closely to the vehicle in front. }
}
@article{Kattan20111887,
title = {Managing speed at school and playground zones },
journal = {Accident Analysis & Prevention },
volume = {43},
number = {5},
pages = {1887 - 1891},
year = {2011},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2011.04.009},
url = {http://www.sciencedirect.com/science/article/pii/S000145751100090X},
author = {Lina Kattan and Richard Tay and Shanti Acharjee},
keywords = {Road safety},
keywords = {School zone},
keywords = {Playground zone},
keywords = {Speed },
abstract = {Since speeding is one of the major causes of frequent and severe traffic accidents around school and playground areas, many jurisdictions have reduced the speed limits in these areas to protect children who may be at risk. This paper investigated the speed compliance, mean speed and 85th percentile speed at selected school and playground zones in the City of Calgary in Alberta. Our results showed that the mean speed was lower and the rate of compliance was higher in the school zone compared to the playground zone, 2 lane roads relative to 4 lane roads, roads with fencing, traffic control devices and the presence of speed display device or children, and zones that were longer (>200 m). Accordingly, this study provided recommendations to improve the effectiveness of school and playground zone speed limits. }
}
@article{Tay2011483,
title = {Effects of roadside memorials on traffic flow },
journal = {Accident Analysis & Prevention },
volume = {43},
number = {1},
pages = {483 - 486},
year = {2011},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2010.08.026},
url = {http://www.sciencedirect.com/science/article/pii/S0001457510002599},
author = {Richard Tay and Anthony Churchill and Alexandre G. de Barros},
keywords = {Road safety},
keywords = {Roadside memorials},
keywords = {Collisions },
abstract = {Despite their growing popularity in North America, little research has been conducted on understanding the effects of roadside memorials on drivers’ behaviour. In this study, we examined the short-term effects of roadside memorials on traffic speed and headways on a high speed intercity freeway as well as its long-term effect on traffic speed on a high speed urban freeway. Our study found that the placement of roadside memorials did not have any significant effect on traffic speeds or headways, either in the short or long term. Therefore, concerns about the negative effects on driver behaviour were not supported by this research, at least with regards to speeding and following too closely. However, no positive effects on safety were found either. }
}
@article{Rifaat2011276,
title = {Effect of street pattern on the severity of crashes involving vulnerable road users },
journal = {Accident Analysis & Prevention },
volume = {43},
number = {1},
pages = {276 - 283},
year = {2011},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2010.08.024},
url = {http://www.sciencedirect.com/science/article/pii/S0001457510002575},
author = {Shakil Mohammad Rifaat and Richard Tay and Alexandre de Barros},
keywords = {Street pattern},
keywords = {Cyclists},
keywords = {Pedestrians},
keywords = {Collision severity },
abstract = {Road crashes not only claim lives and inflict injuries but also create an economic burden to the society due to loss of productivity. Although numerous studies have been conducted to examine a multitude of factors contributing to the frequency and severity of crashes, very few studies have examined the influence of street pattern at a community level. This study examined the effect of different street patterns on crash severity using the City of Calgary as a case study. In this study, street pattern is classified into four categories: grid-iron, warped parallel, loops and lollipops, and mixed patterns. Their effects on injury risk are examined together with other factors including road features, drivers’ characteristics, crash characteristics, environmental conditions and vehicle attributes. Pedestrian and bicycle crash data for the years 2003–2005 were utilized to develop a multinomial logit model of crash severity. Our results showed that compared to other street patterns, loops and lollipops design increases the probability of an injury but reduces the probability of fatality and property-damage-only in an event of a crash. }
}
@article{Tay2009227,
title = {Factors contributing to hit-and-run in fatal crashes },
journal = {Accident Analysis & Prevention },
volume = {41},
number = {2},
pages = {227 - 233},
year = {2009},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2008.11.002},
url = {http://www.sciencedirect.com/science/article/pii/S0001457508002194},
author = {Richard Tay and Upal Barua and Lina Kattan},
keywords = {Road safety},
keywords = {Hit-and-run},
keywords = {Logistic regression},
keywords = {California },
abstract = {Hit-and-run in a collision is a punishable offence as it delays crash notification thereby delaying emergency response which increases the likelihood of traffic fatality. To obtain a better understanding of hit-and-run behavior, a logistic regression model has been applied in this study to identify the factors that might affect the occurrence of hit-and-run in fatal crashes in California, USA. Our results show that roadway functional class, routes, traffic flow, types of roadway section, speed limit, traffic control device, functioning of traffic control device, lighting condition, roadway alignment and roadway profile are important determinants that engineers can target to reduce hit-and-run in fatal crashes. In addition, targeted traffic enforcement should be performed on weekends and nighttime. }
}
@article{TAY200956,
title = {Evaluation of Pictograms in Dynamic Lane Control Systems in the Republic of Korea },
journal = {Journal of Transportation Systems Engineering and Information Technology },
volume = {9},
number = {2},
pages = {56 - 61},
year = {2009},
note = {},
issn = {1570-6672},
doi = {http://dx.doi.org/10.1016/S1570-6672(08)60054-9},
url = {http://www.sciencedirect.com/science/article/pii/S1570667208600549},
author = {Richard TAY and Jaisung CHOI},
keywords = {pictogram},
keywords = {variable message signs},
keywords = {lane control systems},
keywords = {driver perceptions },
abstract = {Pictograms have increasingly been used in electronic message display boards around the world as part of the intelligent transportation systems because they provide drivers with a clear and precise message that is easy to understand. This article reports on an evaluation of pictograms for a dynamic traffic control system in Seoul, Republic of Korea. In this study, some of the pictograms developed in an earlier study were redesigned and transferred to an actual variable message sign for a field test. In addition, drivers' perceptions of these pictograms were also elicited from a convenient sample to provide useful information to assist in the final selection of the pictograms. The study found that most of the pictograms were quite easy to comprehend. However, pictograms depicting accidents performed poorly, with only 10.0% and 43.5% of the participants correctly identifying the message conveyed by the European design and the existing \{ROK\} design, respectively. The pictograms depicting congestion and traffic incidents also performed moderately, with only 45%–55% correctly identifying the message conveyed. Finally, the European design for snow warning performed poorly (17.5% correct), whereas the \{ROK\} design performed relatively well (75.5% correct). }
}
@article{Tan200854,
title = {Sources contributing to PM2.5 in a commercial truck cabin in winter },
journal = {Transportation Research Part D: Transport and Environment },
volume = {13},
number = {1},
pages = {54 - 58},
year = {2008},
note = {},
issn = {1361-9209},
doi = {http://dx.doi.org/10.1016/j.trd.2007.08.001},
url = {http://www.sciencedirect.com/science/article/pii/S1361920907000880},
author = {Zhongchao Tan and Richard Tay},
keywords = {Commercial truck cabin},
keywords = {PM2.5},
keywords = {Metal scan },
abstract = {This study determined the sources of the fine-mode airborne particles in a commercial truck cabin through chemical composition analyses of samples taken over a month during winter time in Alberta, Canada. The main sources of the PM2.5 in this cabin identified through a metal scan were engine emissions, fine road dust, and metal processing plants. }
}
@article{Tay20081330,
title = {A logistic model of the effects of roadway, environmental, vehicle, crash and driver characteristics on hit-and-run crashes },
journal = {Accident Analysis & Prevention },
volume = {40},
number = {4},
pages = {1330 - 1336},
year = {2008},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2008.02.003},
url = {http://www.sciencedirect.com/science/article/pii/S0001457508000249},
author = {Richard Tay and Shakil Mohammad Rifaat and Hoong Chor Chin},
keywords = {Hit-and-run},
keywords = {Logistic model},
keywords = {Singapore },
abstract = {Leaving the scene of a crash without reporting it is an offence in most countries and many studies have been devoted to improving ways to identify hit-and-run vehicles and the drivers involved. However, relatively few studies have been conducted on identifying factors that contribute to the decision to run after the crash. This study identifies the factors that are associated with the likelihood of hit-and-run crashes including driver characteristics, vehicle types, crash characteristics, roadway features and environmental characteristics. Using a logistic regression model to delineate hit-and-run crashes from nonhit-and-run crashes, this study found that drivers were more likely to run when crashes occurred at night, on a bridge and flyover, bend, straight road and near shop houses; involved two vehicles, two-wheel vehicles and vehicles from neighboring countries; and when the driver was a male, minority, and aged between 45 and 69. On the other hand, collisions involving right turn and U-turn maneuvers, and occurring on undivided roads were less likely to be hit-and-run crashes. }
}
@article{Koo201044,
title = {Ground travel mode choices of air arrivals at regional destinations: The significance of tourism attributes and destination contexts },
journal = {Research in Transportation Economics },
volume = {26},
number = {1},
pages = {44 - 53},
year = {2010},
note = {Economics of Transport for Tourism },
issn = {0739-8859},
doi = {http://dx.doi.org/10.1016/j.retrec.2009.10.007},
url = {http://www.sciencedirect.com/science/article/pii/S0739885909000547},
author = {Tay T.R. Koo and Cheng-Lung (Richard) Wu and Larry Dwyer},
keywords = {Transport mode choice},
keywords = {Regional dispersal},
keywords = {Regional tourism},
keywords = {Stated choice experiment},
keywords = {Logit model },
abstract = {The aim of this paper is to examine the air leisure arrivals’ ground travel mode choice in the context of their decision to disperse beyond the gateway. A stated choice experiment was designed to examine the dispersal and travel mode choice of leisure visitors arriving on air transport at Cairns. Results show that for a hypothetical public bus alternative, attributes such as ‘sightseeing opportunities’ and ‘driver quality’ were significant for trips made to less known destinations located south of Cairns, compared to destinations north of Cairns. Findings suggest that while travel mode attributes and trip characteristics are significant determinants of the mode choice of air leisure arrivals, the extent of their significance varied markedly across destinations. Although the data examined in this paper were collected in Cairns, this research should be of relevance to many regions interested in understanding the relationship between destination transport and dispersal of air arrivals. }
}
@article{TAY201018,
title = {Effectiveness of Road Safety Messages on Variable Message Signs },
journal = {Journal of Transportation Systems Engineering and Information Technology },
volume = {10},
number = {3},
pages = {18 - 23},
year = {2010},
note = {},
issn = {1570-6672},
doi = {http://dx.doi.org/10.1016/S1570-6672(09)60040-4},
url = {http://www.sciencedirect.com/science/article/pii/S1570667209600404},
author = {Richard TAY and Alex DE BARROS},
keywords = {traffic engineering},
keywords = {information technology},
keywords = {variable message sign},
keywords = {speeding},
keywords = {road safety messages},
keywords = {driver behavior },
abstract = {Despite being promoted as a means to improve the efficiency and safety of the road network, the focus of most advanced technologies thus far has been on improving mobility rather than safety. For example, variable message signs are often installed for the sole purpose of providing travel advices to drivers even though they can be used to communicate a wide variety of messages. However, once installed, it is simply communication device and could be used for promoting road safety when not used to display traffic related information. This study examines the effects of some anti-speeding messages on driver attitudes and traffic speed on an inter-city highway. A questionnaire survey was developed and administered to a sample of nearly 100 drivers. The test site chosen for this quasi-experiment was Highway 2 between the Cities of Edmonton and Calgary. The study showed that the messages developed have only a relatively small albeit beneficial effect on driver attitudes and on-road traffic speed. }
}
@article{Tay2009663,
title = {Drivers’ perceptions and reactions to roadside memorials },
journal = {Accident Analysis & Prevention },
volume = {41},
number = {4},
pages = {663 - 669},
year = {2009},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2009.03.006},
url = {http://www.sciencedirect.com/science/article/pii/S0001457509000517},
author = {Richard Tay},
keywords = {Road safety},
keywords = {Roadside memorials},
keywords = {Red light running },
abstract = {Despite their growing popularity in North America, little research has been conducted on understanding the effects of roadside memorials on drivers’ behaviour. In this study, an online survey of 810 drivers found that public opinions on the policy options as well as drivers’ self-reported reactions to the presence of roadside memorials were fairly divided. In addition, an on-road experiment was conducted to examine the short term effects of roadside memorials at two intersections. Our results showed that the number of red light violations was reduced by 16.7% in the 6 weeks after the installation of the mock memorials compared to the 6 weeks before whereas the number of violations at two comparison sites experienced an increase of 16.8%. }
}
@article{Tay200526,
title = {Mass media campaigns reduce the incidence of drinking and driving },
journal = {Evidence-based Healthcare and Public Health },
volume = {9},
number = {1},
pages = {26 - 29},
year = {2005},
note = {},
issn = {1744-2249},
doi = {http://dx.doi.org/10.1016/j.ehbc.2004.11.013},
url = {http://www.sciencedirect.com/science/article/pii/S1744224904002360},
author = {Richard Tay},
keywords = {Accident prevention},
keywords = {Alcohol impaired driving},
keywords = {Car crashes},
keywords = {Drinking and driving},
keywords = {Mass media campaigns},
keywords = {Systematic review },
abstract = {Question Do mass media campaigns result in reduced drunk-driving and alcohol-related crashes? Study Design Systematic review with meta-analysis. Main results Eight of 11 studies identified met inclusion criteria. Mass media campaigns on drink driving reduce alcohol-related crashes in the period during or after the campaign (median decease: 13%; interquartile range [IQR] 6% to 14%; see Results table). Mass media campaigns reduced crashes resulting in injury by a median of 10% (IQR 6% to 15%). Mass media campaigns resulted in large savings in medical costs, property damage and productivity (Victoria campaign cost $403,174 per month versus savings of $8,324,532 per month; Wichita campaign cost $454,060 versus savings of $3,431,305; Kansas City campaign cost $322,660 versus savings of $3,676,399). There were no significant differences in outcomes among message types emphasising legal, social or health consequences of drunk-driving. Authors’ conclusions Mass media campaigns significantly reduce drunk-driving and alcohol-related crashes. These campaigns result in large savings. }
}
@article{Tay20082065,
title = {Marginal effect of increasing ageing drivers on injury crashes },
journal = {Accident Analysis & Prevention },
volume = {40},
number = {6},
pages = {2065 - 2068},
year = {2008},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2008.07.012},
url = {http://www.sciencedirect.com/science/article/pii/S0001457508001267},
author = {Richard Tay},
keywords = {Marginal effects},
keywords = {Ageing drivers},
keywords = {Injury crashes},
keywords = {Licensing },
abstract = {The safety effects of the ageing driving population have been a topic of research interests in health and transportation economics in recent years due to the ageing of the baby boomers. This study adds to the current knowledge by examining the marginal effects of changing the driver mix on injury crashes using data from the Canadian Province of Alberta between 1990 and 2004. Results from a Poisson regression model reveal that increasing the number of young and ageing drivers will result in an increase in the number of injury crashes whereas increasing the number of middle-aged drivers will result in a reduction. These results are in contrast to those obtained in a previous study on the marginal effects of changing the driver mix on fatal crashes in the Australian State of Queensland and some possible explanations for the differing results are provided. }
}
@article{TAY200198,
title = {\{CENTRE\} \{FOR\} \{ACCIDENT\} \{RESEARCH\} \{AND\} \{ROAD\} \{SAFETY\} },
journal = {\{IATSS\} Research },
volume = {25},
number = {2},
pages = {98 - 99},
year = {2001},
note = {},
issn = {0386-1112},
doi = {http://dx.doi.org/10.1016/S0386-1112(14)60076-5},
url = {http://www.sciencedirect.com/science/article/pii/S0386111214600765},
author = {Richard TAY}
}
@article{TAY200489,
title = {\{DRIVER\} INATTENTION: Drivers' Perception of Risks and Compensating Behaviours },
journal = {\{IATSS\} Research },
volume = {28},
number = {1},
pages = {89 - 94},
year = {2004},
note = {},
issn = {0386-1112},
doi = {http://dx.doi.org/10.1016/S0386-1112(14)60095-9},
url = {http://www.sciencedirect.com/science/article/pii/S0386111214600959},
author = {Richard TAY and David KNOWLES},
keywords = {Driver inattention},
keywords = {Risk perception},
keywords = {Self-regulation},
keywords = {Risk compensation },
abstract = {Driver inattention, especially driver distraction, is an extremely influential but generally neglected contributing factor of road crashes. This paper explores some of the common behaviours associated with several common forms of driver inattention, with respect to their perceived crash risks, rates of self-reported behaviours and whether drivers regulate such behaviours depending on the road and traffic environment, and provides some policy recommendations to address issues raised. }
}
@article{Tay2005922,
title = {The effectiveness of enforcement and publicity campaigns on serious crashes involving young male drivers: Are drink driving and speeding similar? },
journal = {Accident Analysis & Prevention },
volume = {37},
number = {5},
pages = {922 - 929},
year = {2005},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2005.04.010},
url = {http://www.sciencedirect.com/science/article/pii/S0001457505000734},
author = {Richard Tay},
keywords = {Traffic enforcement},
keywords = {Road safety advertising},
keywords = {Young male drivers},
keywords = {Speeding},
keywords = {Drink driving },
abstract = {This study re-evaluated the effectiveness of the anti-drink driving and anti-speeding enforcement and publicity campaigns implemented in the Australian State of Victoria which have thus far yielded mixed results in several evaluations. As opposed to previous evaluations, this study focused on the effects of these campaigns on young male drivers who formed the primary target and examined the combined effects of the campaigns on the total number of serious crashes. Our results showed that the anti-drink driving enforcement and publicity campaigns had a significant independent effect in reducing crashes but their interactive effect was anti-complementary. Conversely, the anti-speeding enforcement and publicity campaigns had no independent effect but their interactive effect was significant in reducing serious crashes involving young male drivers. }
}
@article{Newnam2006809,
title = {Using psychological frameworks to inform the evaluation of fleet safety initiatives },
journal = {Safety Science },
volume = {44},
number = {9},
pages = {809 - 820},
year = {2006},
note = {},
issn = {0925-7535},
doi = {http://dx.doi.org/10.1016/j.ssci.2006.04.003},
url = {http://www.sciencedirect.com/science/article/pii/S0925753506000506},
author = {Sharon Newnam and Richard Tay and Claire Mason},
keywords = {Work-related driving},
keywords = {Fleet safety},
keywords = {Persuasive communication},
keywords = {Performance pricing },
abstract = {Despite its importance, relatively little past research has investigated the effectiveness of fleet safety initiatives and their impact on drivers’ attitudes and work-related driving outcomes within a strong theoretical framework. This study conceptualised the social–psychological processes underlying two fleet safety initiatives, and hypothesised that these processes could be used to explain the effects of the fleet safety initiatives on changes in attitudes. Twenty-four fleet managers participated in the study and the results suggested that the effectiveness of the fleet safety initiatives in changing fleet managers’ attitudes toward the management of fleet safety could be explained through some of the processes underlying the persuasive communication and behavior management frameworks. Finally, some implications for designing and improving fleet safety initiatives were discussed. }
}
@article{Tay2006112,
title = {Ageing drivers: Storm in a teacup? },
journal = {Accident Analysis & Prevention },
volume = {38},
number = {1},
pages = {112 - 121},
year = {2006},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2005.07.009},
url = {http://www.sciencedirect.com/science/article/pii/S000145750500134X},
author = {Richard Tay},
keywords = {Road safety},
keywords = {Ageing drivers},
keywords = {Licensing},
keywords = {Marginal effects},
keywords = {Australia},
keywords = {Econometrics },
abstract = {The purpose of this paper is to address two important issues regarding ageing drivers. First, there is a presumption in the road safety arena that the expected increase in the number of ageing drivers on the roads will lead to an increase in crashes. Second, despite extensive research on ageing drivers, especially on their increased vulnerability and reduced driving abilities, the most widely recommended road safety strategy relates to the control of their driving licenses. This presumption and the associated policy recommendation are based mainly on the higher relative crash risks associated with ageing drivers compared to their younger counterparts. This study, however, argues that the average crash risks obtained in previous studies provide only indirect information concerning these issues and any decision based on these results may produce unexpected outcomes. An analytical framework to examine the marginal effect of changing the driver mix on the roads is proposed and a simple empirical model is estimated as an illustration. In contrast to previous studies, we found that increasing the number of licenses issued to ageing drivers had only an insignificant impact on the number of fatal crashes on the roads, suggesting that the concern over ageing drivers may be a storm in a teacup. }
}
@article{Tay2005259,
title = {Drink driving enforcement and publicity campaigns: are the policy recommendations sensitive to model specification? },
journal = {Accident Analysis & Prevention },
volume = {37},
number = {2},
pages = {259 - 266},
year = {2005},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2004.10.001},
url = {http://www.sciencedirect.com/science/article/pii/S0001457504000909},
author = {Richard Tay},
keywords = {Road safety},
keywords = {Drink driving},
keywords = {Enforcement},
keywords = {Publicity campaigns },
abstract = {Since their implementation, the drink driving enforcement and publicity campaigns in the Australian State of Victoria have been extensively evaluated and the mixed results obtained have generated much public debate. Using the same data from previous studies, this paper re-evaluated the effectiveness of the campaigns and tested several model assumptions and specifications. In general, the results obtained were robust and showed that the campaigns were effective in reducing serious crashes during high alcohol hours. }
}
@article{McCarthy2005373,
title = {Road safety, alcohol and public policy },
journal = {Transportation Research Part E: Logistics and Transportation Review },
volume = {41},
number = {5},
pages = {373 - 376},
year = {2005},
note = {Road Safety, Alcohol and Public Policy },
issn = {1366-5545},
doi = {http://dx.doi.org/10.1016/j.tre.2005.03.006},
url = {http://www.sciencedirect.com/science/article/pii/S1366554505000281},
author = {Patrick McCarthy and Richard Tay}
}
@article{Cheng2006389,
title = {Air quality in a commercial truck cabin },
journal = {Transportation Research Part D: Transport and Environment },
volume = {11},
number = {6},
pages = {389 - 395},
year = {2006},
note = {},
issn = {1361-9209},
doi = {http://dx.doi.org/10.1016/j.trd.2006.07.005},
url = {http://www.sciencedirect.com/science/article/pii/S1361920906000514},
author = {Xiaoying Cheng and Zhongchao Tan and Xinlei Wang and Richard Tay},
keywords = {Air quality},
keywords = {Occupational exposure},
keywords = {Commercial truck},
keywords = {Indoor air pollution },
abstract = {A survey and in-field measurements were undertaken to examine air quality in truck cabins. Preliminary survey results indicated that 99% of the truck drivers opened their windows for air while driving and they believed that the air was fresh. Field measurements showed that the concentrations of CO, CO2, and \{NO2\} in the truck cabin during a two month monitoring period were lower than their respective recommended values. However, thermal comfort level, as indicated by temperature and relative humidity, was out of the recommended level for 93% of the measurement period. Moreover, readings for PM2.5 were within the range of 66–835 μg/m3 which were 1–13 times the recommended value. }
}
@article{Lewis200748,
title = {Examining the effectiveness of physical threats in road safety advertising: The role of the third-person effect, gender, and age },
journal = {Transportation Research Part F: Traffic Psychology and Behaviour },
volume = {10},
number = {1},
pages = {48 - 60},
year = {2007},
note = {},
issn = {1369-8478},
doi = {http://dx.doi.org/10.1016/j.trf.2006.05.001},
url = {http://www.sciencedirect.com/science/article/pii/S1369847806000374},
author = {Ioni Lewis and Barry Watson and Richard Tay},
keywords = {Road safety advertising},
keywords = {Threat appeals},
keywords = {Third-person effect},
keywords = {Gender },
abstract = {Threatening advertisements have been widely used in the social marketing of road safety. However, despite their popularity and over five decades of research into the fear-persuasion relationship, an unequivocal answer regarding their effectiveness remains unachieved. More contemporary “fear appeal” research has explored the extent other variables moderate this relationship. In this study, the third-person effect was examined to explore its association with the extent male and female drivers reported intentions to adopt the recommendations of two road safety advertisements depicting high physical threats. Drivers (N = 152) first provided responses on pre-exposure future driving intentions, subsequently viewed two advertisements, one anti-speeding and one anti-drink driving, followed by measurement of their perceptions and post-manipulation intentions. The latter measure, post-manipulation intentions, was taken as the level of message acceptance for each advertisement. Results indicated a significant gender difference with females reporting reverse third-person effects (i.e., the messages would have more influence on themselves than others) and males reporting classic third-person effects (i.e., the messages would have more influence on others than themselves). Consistent with such third-person effects, females reported greater intention not to speed and not to drink and drive after being exposed to the advertisements than males. To determine the extent that third-person differential perceptions contributed to explaining variance in post-manipulation intentions, hierarchical regressions were conducted. These regressions revealed that third-person scores significantly contributed to the variance explained in post-manipulation intentions, beyond the contribution of other factors including demographic characteristics, pre-exposure intentions and past behaviour. The theoretical and applied implications of the results are discussed. }
}
@article{SOMASUNDARASWARAN200668,
title = {SELF-REPORTED \{DIFFERENCES\} \{BETWEEN\} CRASH-INVOLVED \{AND\} NON-CRASH-INVOLVED THREE-WHEELER \{DRIVERS\} \{IN\} \{SRI\} \{LANKA\} },
journal = {\{IATSS\} Research },
volume = {30},
number = {1},
pages = {68 - 72},
year = {2006},
note = {},
issn = {0386-1112},
doi = {http://dx.doi.org/10.1016/S0386-1112(14)60157-6},
url = {http://www.sciencedirect.com/science/article/pii/S0386111214601576},
author = {A.K. SOMASUNDARASWARAN and Richard TAY},
keywords = {Road safety},
keywords = {Three-wheelers},
keywords = {Sri Lanka},
keywords = {Driver characteristics},
keywords = {Work conditions },
abstract = {Despite being an important mode of transportation in the developing world, little research has been conducted to understand the factors contributing to crashes involving three wheel vehicles. This study surveyed a convenient sample of 505 professional three-wheeler drivers in Sri Lanka to explore the similarities and differences in the demographic and work characteristics between three-wheeler drivers who reported experiencing at least one collision in the past twelve months and those who reported that they were not involved in any collisions. Our study revealed some interesting results that were quite different from those obtained in the studies on professional drivers in developed countries. In particular, both drivers with less than one year and more than five years of driving experience in our study were found to be associated with higher probability of crash involvement. Also, the number of trips per day and the average travel distance per trip were found to be insignificant in delineating between crash-involved and non-crash-involved drivers. Moreover, crash-involved drivers, on average, have significantly fewer working days per week and fewer hours per day, suggesting that the conventional approach used in most developed countries to tackle fatigue among professional drivers do not appear to be suitable for solving the road safety problem involving three-wheeler drivers in a developing country. Also, since the age of most drivers falls in a narrow range, this U-shaped relationship is not likely to be a result of youth and ageing but of inexperience in newer drivers and complacency in more experienced drivers. Lastly, since a relatively large proportion of the drivers had driven without a valid driving license, legislation and enforcement interventions are likely to be less effective than education and engineering countermeasures. }
}
@article{TAY200292,
title = {\{TIN\} \{CANS\} \{OR\} \{ASSAULT\} VEHICLES?: The Role of Crashworthiness and Non-aggressiveness in Vehicle Safety Design, Promotion and Regulation },
journal = {\{IATSS\} Research },
volume = {26},
number = {2},
pages = {92 - 98},
year = {2002},
note = {},
issn = {0386-1112},
doi = {http://dx.doi.org/10.1016/S0386-1112(14)60048-0},
url = {http://www.sciencedirect.com/science/article/pii/S0386111214600480},
author = {Richard TAY},
keywords = {Road safety},
keywords = {Vehicle safety},
keywords = {Crashworthiness},
keywords = {Non-aggressiveness},
keywords = {Prisoners' dilemma },
abstract = {This paper examines the policy implications of the traditional approach to vehicle safety, which tends to focus on the crashworthiness of a vehicle and its occupant protection capability, and an alternative approach that focuses more on the non-aggressiveness of the vehicle. It is argued that this alternative approach will improve road safety as well as social equity and environmental quality. }
}
@article{Tay1996325,
title = {A portfolio choice model of the demand for recreational trips },
journal = {Transportation Research Part B: Methodological },
volume = {30},
number = {5},
pages = {325 - 337},
year = {1996},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/0191-2615(96)00004-5},
url = {http://www.sciencedirect.com/science/article/pii/0191261596000045},
author = {Richard Tay and Patrick S. McCarthy and Jerald J. Fletcher},
abstract = {Consumer choices of recreational trip-making involve a number of related decisions, including destination, trip frequency, length and timing of trip(s), and choice of mode(s). Previous analyses have generally developed tractable discrete choice models by limiting their focus to one or two decisions and conditioning on the others. The analysis presented in this paper takes a more general perspective by assuming that consumers choose one out of a set of trip portfolios which are made up of alternative destinations, trip frequencies and durations. The model is applied to recreational fishing activities, and produces estimation results that are consistent with the hypothesis of random utility maximization. Choice elasticities are calculated and indicate that portfolio demands are fairly elastic with respect to changes in water qualities and travel costs. }
}
@article{McCarthy1989367,
title = {Consumer valuation of new car attributes: An econometric analysis of the demand for domestic and Japanese/Western European imports },
journal = {Transportation Research Part A: General },
volume = {23},
number = {5},
pages = {367 - 375},
year = {1989},
note = {},
issn = {0191-2607},
doi = {http://dx.doi.org/10.1016/0191-2607(89)90084-8},
url = {http://www.sciencedirect.com/science/article/pii/0191260789900848},
author = {Patrick S. McCarthy and Richard Tay},
abstract = {Although previous studies of new vehicle choice decisions have shown that consumers evaluate the attributes of domestic vehicles differently from those of imported vehicles, the assumption underlying these results is overly restrictive. In particular, there is no reason to assume, a priori, that the attributes of all imported vehicles have similar effects upon consumer choice behavior. A competing hypothesis, for example, is that consumers of U.S. and European automobiles have similar attribute valuations that are differentiated from those of Japanese consumers. In the present paper, a multinomial logit model of vehicle type choice is developed which more completely differentiates imports by country of origin. Using a 1985 national sample of new car buyers to estimate the model, willingness to pay measures were calculated and nested hypothesis tests on attribute valuation performed. The results supported the hypothesis that consumers value vehicle attributes differently depending upon its country of origin. Moreover, consumers do not have similar valuations on the attributes of all imports implying that an arbitrary distinction between domestic and imported vehicles may produce misleading results. }
}
@article{McCarthy199839,
title = {New Vehicle Consumption and Fuel Efficiency: A Nested Logit Approach1 },
journal = {Transportation Research Part E: Logistics and Transportation Review },
volume = {34},
number = {1},
pages = {39 - 51},
year = {1998},
note = {},
issn = {1366-5545},
doi = {http://dx.doi.org/10.1016/S1366-5545(97)00042-2},
url = {http://www.sciencedirect.com/science/article/pii/S1366554597000422},
author = {Patrick S. McCarthy and Richard S. Tay},
keywords = {fuel efficiency},
keywords = {vehicle choice},
keywords = {nested logit },
abstract = {Using data from a 1989 household survey of new vehicle buyers, this paper develops and estimates a nested logit model of new vehicle demands. In comparison with the more restrictive multinomial logit model, which assumes that the error terms are uncorrelated, the results support a nested structure of vehicle choice in which the error terms for purchases within the same fuel efficiency category are correlated. Among the findings, improvements in vehicle size, safety and quality increase a make/model’s demand. Females, lower income households, younger consumers, non-white purchasers, and buyers in more densely populated areas exhibit higher demands for more fuel efficient vehicles. The results also indicate that vehicle demands have an approximate unitary elasticity with respect to capital cost and are elastic with respect to operating costs. }
}
@comment{{Dominique Lord PAPERS}}
@comment{{DOMINIQUE LORD PAPERS}}
@article{miaou2003modeling,
title = {Modeling traffic crash-flow relationships for intersections: dispersion parameter, functional form, and Bayes versus empirical Bayes methods},
author = {Miaou, Shaw-Pin and Lord, Dominique},
journal = {Transportation Research Record: Journal of the Transportation Research Board},
volume = {1840},
number = {1},
pages = {31--40},
year = {2003},
publisher = {Trans Res Board}
}
@article{persaud2001safety,
title = {Safety effect of roundabout conversions in the united states: Empirical bayes observational before-after study},
author = {Persaud, Bhagwant N and Retting, Richard A and Garder, Per E and Lord, Dominique},
journal = {Transportation Research Record: Journal of the Transportation Research Board},
volume = {1751},
number = {1},
pages = {1--8},
year = {2001},
publisher = {Trans Res Board}
}
@article{park2007multivariate,
title = {Multivariate Poisson-lognormal models for jointly modeling crash frequency by severity},
author = {Park, Eun Sug and Lord, Dominique},
journal = {Transportation Research Record: Journal of the Transportation Research Board},
volume = {2019},
number = {1},
pages = {1--6},
year = {2007},
publisher = {Trans Res Board}
}
@article{retting2001crash,
title = {Crash and injury reduction following installation of roundabouts in the United States.},
author = {Retting, Richard A and Persaud, Bhagwant N and Garder, Per E and Lord, Dominique},
journal = {American Journal of Public Health},
volume = {91},
number = {4},
pages = {628},
year = {2001},
publisher = {American Public Health Association}
}
@article{persaud2002calibration,
title = {Calibration and transferability of accident prediction models for urban intersections},
author = {Persaud, Bhagwant and Lord, Dominique and Palmisano, Joseph},
journal = {Transportation Research Record: Journal of the Transportation Research Board},
volume = {1784},
number = {1},
pages = {57--64},
year = {2002},
publisher = {Trans Res Board}
}
@article{lord2005calibration,
title = {Calibration of predictive models for estimating safety of ramp design configurations},
author = {Lord, Dominique and Bonneson, James A},
journal = {Transportation Research Record: Journal of the Transportation Research Board},
volume = {1908},
number = {1},
pages = {88--95},
year = {2005},
publisher = {Trans Res Board}
}
@article{brewer2006exploration,
title = {Exploration of pedestrian gap-acceptance behavior at selected locations},
author = {Brewer, Marcus A and Fitzpatrick, Kay and Whitacre, Jeffrey A and Lord, Dominique},
journal = {Transportation Research Record: Journal of the Transportation Research Board},
volume = {1982},
number = {1},
pages = {132--140},
year = {2006},
publisher = {Trans Res Board}
}
@techreport{lord2008methodology,
title = {Methodology to predict the safety performance of rural multilane highways},
author = {Lord, Dominique and Geedipally, Srinivas Reddy and Persaud, Bhagwant N and Washington, Simon P and van Schalkwyk, Ida and Ivan, John N and Lyon, Craig and Jonsson, Thomas},
year = {2008}
}
@article{ye2011investigation,
title = {Investigation of effects of underreporting crash data on three commonly used traffic crash severity models},
author = {Ye, Fan and Lord, Dominique},
journal = {Transportation Research Record: Journal of the Transportation Research Board},
volume = {2241},
number = {1},
pages = {51--58},
year = {2011},
publisher = {Trans Res Board}
}
@article{miaou2005part,
title = {Part 1: Roadside Safety Design: Developing Guidelines for Median Barrier Installation: Benefit-Cost Analysis with Texas Data},
author = {Miaou, Shaw-Pin and Bligh, Roger P and Lord, Dominique},
journal = {Transportation Research Record: Journal of the Transportation Research Board},
volume = {1904},
number = {1},
pages = {2--19},
year = {2005},
publisher = {Trans Res Board}
}
@article{lord2002application,
title = {Application of accident prediction models for computation of accident risk on transportation networks},
author = {Lord, Dominique},
journal = {Transportation Research Record: Journal of the Transportation Research Board},
volume = {1784},
number = {1},
pages = {17--26},
year = {2002},
publisher = {Trans Res Board}
}
@article{lord2010extension,
title = {Extension of the Application of Conway-Maxwell-Poisson Models: Analyzing Traffic Crash Data Exhibiting Underdispersion},
author = {Lord, Dominique and Geedipally, Srinivas Reddy and Guikema, Seth D},
journal = {Risk Analysis},
volume = {30},
number = {8},
pages = {1268--1276},
year = {2010},
publisher = {Wiley Online Library}
}
@article{lord2005does,
title = {Does separating trucks from other traffic improve overall safety?},
author = {Lord, Dominique and Middleton, Dan and Whitacre, Jeffrey},
journal = {Transportation Research Record: Journal of the Transportation Research Board},
volume = {1922},
number = {1},
pages = {156--166},
year = {2005},
publisher = {Trans Res Board}
}
@article{persaud2003development,
title = {Development of a procedure for estimating expected safety effects of a contemplated traffic signal installation},
author = {Persaud, Bhagwant and McGee, Hugh and Lyon, Craig and Lord, Dominique},
journal = {Transportation Research Record: Journal of the Transportation Research Board},
volume = {1840},
number = {1},
pages = {96--103},
year = {2003},
publisher = {Trans Res Board}
}
@article{miaou2005developing,
title = {Developing guidelines for median barrier installation: benefit-cost analysis with Texas data},
author = {Miaou, Shaw-Pin and Bligh, Roger P and Lord, Dominique},
journal = {Transportation research record},
volume = {1904},
pages = {3--19},
year = {2005},
publisher = {Transportation Research Board, National Research Council, National Academy of Sciences USA}
}
@article{park2008adjustment,
title = {Adjustment for maximum likelihood estimate of negative binomial dispersion parameter},
author = {Park, Byung-Jung and Lord, Dominique},
journal = {Transportation Research Record: Journal of the Transportation Research Board},
volume = {2061},
number = {1},
pages = {9--19},
year = {2008},
publisher = {Trans Res Board}
}
@article{Zou20151,
title = {Modeling over-dispersed crash data with a long tail: Examining the accuracy of the dispersion parameter in Negative Binomial models },
journal = {Analytic Methods in Accident Research },
volume = {5},
number = {0},
pages = {1 - 16},
year = {2015},
note = {},
issn = {2213-6657},
doi = {http://dx.doi.org/10.1016/j.amar.2014.12.002},
url = {http://www.sciencedirect.com/science/article/pii/S2213665715000020},
author = {Yajie Zou and Lingtao Wu and Dominique Lord},
keywords = {Sichel},
keywords = {Negative Binomial},
keywords = {Dispersion parameter},
keywords = {Traffic crashes},
keywords = {Empirical Bayes },
abstract = {Abstract Despite many statistical models that have been proposed for modeling motor vehicle crashes, the most commonly used statistical tool remains the Negative Binomial (NB) model. Crash data collected for safety studies may exhibit over-dispersion and a long tail (i.e., a few sites have unusually high number of crashes). However, some studies have shown that \{NB\} models cannot handle over-dispersed count data with a long tail adequately. So far, no work has investigated the performance of the dispersion parameter of the \{NB\} model when analyzing over-dispersed crash data with a long tail. The dispersion parameter of the \{NB\} model plays an important role in various types of transportation safety analysis. The first objective of this study is to examine whether the dispersion parameter can truly reflect the level of dispersion in over-dispersed crash data with a long tail. The second objective is to determine whether the dispersion term of the Sichel (SI) model can be used as an alternative to the dispersion parameter of the \{NB\} model. To accomplish the objectives of this study, crash data sets are simulated from \{NB\} and \{SI\} regression models using different values describing the mean and the dispersion level. For the simulated data sets, the dispersion parameter and dispersion term are estimated and compared to the true values. To complement the output of the simulation study, crash data collected in Texas are also used to compare the dispersion parameter and dispersion term. The results from this study suggest that the dispersion parameter of the \{NB\} model can erroneously estimate the level of dispersion in over-dispersed count data with a long tail and the dispersion term of the \{SI\} model is more reliable in estimating the true level of dispersion. Thus, considering the findings in this study, it is believed that the dispersion term may offer a viable alternative for analyzing over-dispersed crash data with a long tail. }
}
@article{Park2014319,
title = {Finite mixture modeling for vehicle crash data with application to hotspot identification },
journal = {Accident Analysis & Prevention },
volume = {71},
number = {0},
pages = {319 - 326},
year = {2014},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2014.05.030},
url = {http://www.sciencedirect.com/science/article/pii/S0001457514001729},
author = {Byung-Jung Park and Dominique Lord and Chungwon Lee},
keywords = {Finite mixture model},
keywords = {Negative binomial},
keywords = {Overdispersion},
keywords = {Vehicle crash data},
keywords = {Hotspot identification},
keywords = {False positive and negative },
abstract = {Abstract The application of finite mixture regression models has recently gained an interest from highway safety researchers because of its considerable potential for addressing unobserved heterogeneity. Finite mixture models assume that the observations of a sample arise from two or more unobserved components with unknown proportions. Both fixed and varying weight parameter models have been shown to be useful for explaining the heterogeneity and the nature of the dispersion in crash data. Given the superior performance of the finite mixture model, this study, using observed and simulated data, investigated the relative performance of the finite mixture model and the traditional negative binomial (NB) model in terms of hotspot identification. For the observed data, rural multilane segment crash data for divided highways in California and Texas were used. The results showed that the difference measured by the percentage deviation in ranking orders was relatively small for this dataset. Nevertheless, the ranking results from the finite mixture model were considered more reliable than the \{NB\} model because of the better model specification. This finding was also supported by the simulation study which produced a high number of false positives and negatives when a mis-specified model was used for hotspot identification. Regarding an optimal threshold value for identifying hotspots, another simulation analysis indicated that there is a discrepancy between false discovery (increasing) and false negative rates (decreasing). Since the costs associated with false positives and false negatives are different, it is suggested that the selected optimal threshold value should be decided by considering the trade-offs between these two costs so that unnecessary expenses are minimized. }
}
@article{Peng201420,
title = {Applying the Generalized Waring model for investigating sources of variance in motor vehicle crash analysis },
journal = {Accident Analysis & Prevention },
volume = {73},
number = {0},
pages = {20 - 26},
year = {2014},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2014.07.031},
url = {http://www.sciencedirect.com/science/article/pii/S0001457514002346},
author = {Yichuan Peng and Dominique Lord and Yajie Zou},
keywords = {Generalized Waring model},
keywords = {Negative binomial model},
keywords = {Over dispersion},
keywords = {Randomness},
keywords = {Liability},
keywords = {Proneness},
keywords = {Crash modeling },
abstract = {Abstract As one of the major analysis methods, statistical models play an important role in traffic safety analysis. They can be used for a wide variety of purposes, including establishing relationships between variables and understanding the characteristics of a system. The purpose of this paper is to document a new type of model that can help with the latter. This model is based on the Generalized Waring (GW) distribution. The \{GW\} model yields more information about the sources of the variance observed in datasets than other traditional models, such as the negative binomial (NB) model. In this regards, the \{GW\} model can separate the observed variability into three parts: (1) the randomness, which explains the model's uncertainty; (2) the proneness, which refers to the internal differences between entities or observations; and (3) the liability, which is defined as the variance caused by other external factors that are difficult to be identified and have not been included as explanatory variables in the model. The study analyses were accomplished using two observed datasets to explore potential sources of variation. The results show that the \{GW\} model can provide meaningful information about sources of variance in crash data and also performs better than the \{NB\} model. }
}
@article{Flask201447,
title = {A segment level analysis of multi-vehicle motorcycle crashes in Ohio using Bayesian multi-level mixed effects models },
journal = {Safety Science },
volume = {66},
number = {0},
pages = {47 - 53},
year = {2014},
note = {},
issn = {0925-7535},
doi = {http://dx.doi.org/10.1016/j.ssci.2013.12.006},
url = {http://www.sciencedirect.com/science/article/pii/S0925753513003123},
author = {Thomas Flask and William H. Schneider IV and Dominique Lord},
keywords = {Hierarchical Bayes},
keywords = {Spatial random effects},
keywords = {Uncorrelated random effects},
keywords = {Negative binomial model},
keywords = {Conditional autoregressive distribution},
keywords = {Mixed effects },
abstract = {Abstract Multi-vehicle motorcycle crashes combine elements of design, behavior, and traffic. One challenge with working with motorcycle data are the inherit difficulties associated with missing data – such as motorcycle-specific: vehicle miles traveled (VMT) and average daily traffic (ADT). To address the challenges of the missing data, a random effects Bayesian negative binomial model is developed for the state of Ohio. In this study, the random effect terms improve the general model by describing the spatial correlation with fixed effects, the neighborhood criteria, and the uncorrelated heterogeneity for all the multi-vehicle motorcycle crashes that occurred on the 32,289 state-maintained roadway segments in Ohio. Some key findings from this study include regional data improves the goodness-of-fit, and further improvement of the models may be gained through a distance-based neighborhood specification of conditional autoregressive (CAR). In addition to the model improvement using the random effect terms, key variables such as smaller lane and shoulder widths, increases in the horizontal degree of curvature and increases in the maximum vertical grade will increase the prediction of a crash. }
}
@article{Ye201378,
title = {Goodness-of-fit testing for accident models with low means },
journal = {Accident Analysis & Prevention },
volume = {61},
number = {0},
pages = {78 - 86},
year = {2013},
note = {Emerging Research Methods and Their Application to Road Safety Emerging Issues in Safe and Sustainable Mobility for Older Persons The Candrive/Ozcandrive Prospective Older Driver Study: Methodology and Early Study Findings },
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2012.11.007},
url = {http://www.sciencedirect.com/science/article/pii/S0001457512003843},
author = {Zhirui Ye and Yunlong Zhang and Dominique Lord},
keywords = {Low sample mean crash data},
keywords = {Generalized linear model},
keywords = {Goodness-of-fit},
keywords = {Power-divergence },
abstract = {The modeling of relationships between motor vehicle crashes and underlying factors has been investigated for more than three decades. Recently, many highway safety studies have documented the use of negative binomial (NB) regression models. On rare occasions, the Poisson model may be the only alternative especially when crash sample mean is low. Pearson's \{X2\} and the scaled deviance (G2) are two common test statistics that have been proposed as measures of goodness-of-fit (GOF) for Poisson or \{NB\} models. Unfortunately, transportation safety analysts often deal with crash data that are characterized by low sample mean values. Under such conditions, the traditional test statistics may not perform very well. This study has three objectives. The first objective is to examine all the traditional test statistics and compare their performance for the \{GOF\} of accident models subjected to low sample means. Secondly, this study proposes a new test statistic that is not dependent on the sample size for Poisson regression model, as opposed to the grouped \{G2\} method. The proposed method is easy to use and does not require grouping data, which is time consuming and may not be feasible to use if the sample size is small. Moreover, the proposed method can be used for lower sample means than documented in previous studies. Thirdly, this study provides guidance on how and when to use appropriate test statistics for both Poisson and negative binomial (NB) regression models. }
}
@article{Cheng201338,
title = {The Poisson–Weibull generalized linear model for analyzing motor vehicle crash data },
journal = {Safety Science },
volume = {54},
number = {0},
pages = {38 - 42},
year = {2013},
note = {},
issn = {0925-7535},
doi = {http://dx.doi.org/10.1016/j.ssci.2012.11.002},
url = {http://www.sciencedirect.com/science/article/pii/S0925753512002676},
author = {Lingzi Cheng and Srinivas Reddy Geedipally and Dominique Lord},
keywords = {Poisson–Weibull},
keywords = {Poisson–gamma},
keywords = {Generalized linear model},
keywords = {Traffic crashes },
abstract = {Over the last 20–30 years, there has been a significant amount of tools and statistical methods that have been proposed for analyzing crash data. Yet, the Poisson–gamma (PG) is still the most commonly used and widely acceptable model. This paper documents the application of the Poisson–Weibull (PW) generalized linear model (GLM) for modeling motor vehicle crashes. The objectives of this study were to evaluate the application of the \{PW\} \{GLM\} for analyzing this kind of dataset and compare the results with the traditional \{PG\} model. To accomplish the objectives of the study, the modeling performance of the \{PW\} model was first examined using a simulated dataset and then several \{PW\} and \{PG\} \{GLMs\} were developed and compared using two observed crash datasets. The results of this study show that the \{PW\} \{GLM\} performs as well as the \{PG\} \{GLM\} in terms of goodness-of-fit statistics. }
}
@article{Geedipally2014495,
title = {A caution about using deviance information criterion while modeling traffic crashes },
journal = {Safety Science },
volume = {62},
number = {0},
pages = {495 - 498},
year = {2014},
note = {},
issn = {0925-7535},
doi = {http://dx.doi.org/10.1016/j.ssci.2013.10.007},
url = {http://www.sciencedirect.com/science/article/pii/S0925753513002324},
author = {Srinivas Reddy Geedipally and Dominique Lord and Soma Sekhar Dhavala},
keywords = {Deviance information criterion},
keywords = {Poisson-Gamma},
keywords = {Negative binomial},
keywords = {Traffic crashes },
abstract = {Abstract The Poisson-Gamma (PG) or negative binomial (NB) model still remains the most popular method used for analyzing count data. In the software WinBUGS (or any other software used for Bayesian analyses), there are different ways to parameterize the \{NB\} model. In general, either a \{PG\} (based on the Poisson-mixture) or a \{NB\} (based on the Pascal distribution) modeling framework can be used to relate traffic crashes to the explanatory variables. However, it is important to note that the way the model is parameterized will influence the output of the Deviance Information Criterion (DIC) values. The objective of this short study is to document the difference between the \{PG\} and \{NB\} models in the estimation of the DIC. This is especially important given that the NB/PG model is still the most frequently used model in highway safety research and applications. To accomplish the study objective, \{PG\} and \{NB\} models were developed using the crash data collected at 4-legged signalized intersections in Toronto, Ont. The study results showed that there is a considerable difference in the estimation of the \{DIC\} values between the two models. It is thus recommended not to consider the \{DIC\} as the sole model selection criterion and the comparison should be done only between the models that have similar parameterization. Other alternatives such as Bayes Factors, Posterior predictive performance criterion, Bayesian Information Criterion (BIC), among others need to be considered in addition to the \{DIC\} in the model selection. }
}
@article{Zou2013497,
title = {Evaluating the double Poisson generalized linear model },
journal = {Accident Analysis & Prevention },
volume = {59},
number = {0},
pages = {497 - 505},
year = {2013},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2013.07.017},
url = {http://www.sciencedirect.com/science/article/pii/S0001457513002856},
author = {Yaotian Zou and Srinivas Reddy Geedipally and Dominique Lord},
keywords = {Double Poisson},
keywords = {Normalizing constant},
keywords = {Conway–Maxwell–Poisson},
keywords = {Gamma model},
keywords = {Generalized linear model },
abstract = {Abstract The objectives of this study are to: (1) examine the applicability of the double Poisson (DP) generalized linear model (GLM) for analyzing motor vehicle crash data characterized by over- and under-dispersion and (2) compare the performance of the \{DP\} \{GLM\} with the Conway–Maxwell–Poisson (COM-Poisson) \{GLM\} in terms of goodness-of-fit and theoretical soundness. The \{DP\} distribution has seldom been investigated and applied since its first introduction two decades ago. The hurdle for applying the \{DP\} is related to its normalizing constant (or multiplicative constant) which is not available in closed form. This study proposed a new method to approximate the normalizing constant of the \{DP\} with high accuracy and reliability. The \{DP\} \{GLM\} and COM-Poisson \{GLM\} were developed using two observed over-dispersed datasets and one observed under-dispersed dataset. The modeling results indicate that the \{DP\} \{GLM\} with its normalizing constant approximated by the new method can handle crash data characterized by over- and under-dispersion. Its performance is comparable to the COM-Poisson \{GLM\} in terms of goodness-of-fit (GOF), although COM-Poisson \{GLM\} provides a slightly better fit. For the over-dispersed data, the \{DP\} \{GLM\} performs similar to the \{NB\} GLM. Considering the fact that the \{DP\} \{GLM\} can be easily estimated with inexpensive computation and that it is simpler to interpret coefficients, it offers a flexible and efficient alternative for researchers to model count data. }
}
@article{Zou201439,
title = {Analyzing different functional forms of the varying weight parameter for finite mixture of negative binomial regression models },
journal = {Analytic Methods in Accident Research },
volume = {1},
number = {0},
pages = {39 - 52},
year = {2014},
note = {},
issn = {2213-6657},
doi = {http://dx.doi.org/10.1016/j.amar.2013.11.001},
url = {http://www.sciencedirect.com/science/article/pii/S2213665713000079},
author = {Yajie Zou and Yunlong Zhang and Dominique Lord},
keywords = {Negative binomial},
keywords = {Finite mixture model},
keywords = {Dispersion},
keywords = {Weight parameter},
keywords = {Crash data},
keywords = {Heterogeneity },
abstract = {Abstract Factors that cause heterogeneity found in motor vehicle crash data are often unknown to transportation safety researchers and failure to capture this heterogeneity in statistical models can weaken the validity of modeling results. A finite mixture of regression models has been proposed to address the unobserved heterogeneity in crash data, and a fixed weight parameter for these models (i.e., the weight parameter is invariant of the characteristics of the observations under study) is commonly assumed. Recent studies have found that the weight parameter of the finite mixture of negative binomial (NB) models can be dependent upon the functional form of the attributes of the sites, and the selection of the functional form for weight parameter has a significant impact on the classification results. This study investigates the effect of different functional forms on the estimation of the weight parameter as well as the group classification of the finite mixture of \{NB\} regression models, using crash data collected on rural roadway sections in Indiana. A total of 11 different functional forms for the varying weight parameter were estimated; these functional forms include various combinations of traffic flow and segment length as covariates. The results suggest that the modeling of the weight parameter (which essentially helps in improving the group classification) is generally necessary when using the finite mixture of \{NB\} regression models to analyze the crash data, even in the presence of a well-defined mean function. This study also confirms that the selection of the functional form for weight parameter will affect the classification results significantly. Among 11 different functional forms, one functional form, which uses the linear combination of different explanatory variables to model the classification, stands out based on both the goodness-of-fit statistics and the classification results, and is recommended for describing the weight parameter when using the finite mixture of \{NB\} regression models with varying weight parameters to analyze crash data. }
}
@article{MirandaMoreno201331,
title = {Bayesian road safety analysis: Incorporation of past evidence and effect of hyper-prior choice },
journal = {Journal of Safety Research },
volume = {46},
number = {0},
pages = {31 - 40},
year = {2013},
note = {},
issn = {0022-4375},
doi = {http://dx.doi.org/10.1016/j.jsr.2013.03.003},
url = {http://www.sciencedirect.com/science/article/pii/S0022437513000224},
author = {Luis F. Miranda-Moreno and Shahram Heydari and Dominique Lord and Liping Fu},
keywords = {road safety},
keywords = {Bayesian approach},
keywords = {past evidence},
keywords = {hyper-prior assumptions },
abstract = {AbstractProblem This paper aims to address two related issues when applying hierarchical Bayesian models for road safety analysis, namely: (a) how to incorporate available information from previous studies or past experiences in the (hyper) prior distributions for model parameters and (b) what are the potential benefits of incorporating past evidence on the results of a road safety analysis when working with scarce accident data (i.e., when calibrating models with crash datasets characterized by a very low average number of accidents and a small number of sites). Method A simulation framework was developed to evaluate the performance of alternative hyper-priors including informative and non-informative Gamma, Pareto, as well as Uniform distributions. Based on this simulation framework, different data scenarios (i.e., number of observations and years of data) were defined and tested using crash data collected at 3-legged rural intersections in California and crash data collected for rural 4-lane highway segments in Texas. Results This study shows how the accuracy of model parameter estimates (inverse dispersion parameter) is considerably improved when incorporating past evidence, in particular when working with the small number of observations and crash data with low mean. The results also illustrates that when the sample size (more than 100 sites) and the number of years of crash data is relatively large, neither the incorporation of past experience nor the choice of the hyper-prior distribution may affect the final results of a traffic safety analysis. Conclusions As a potential solution to the problem of low sample mean and small sample size, this paper suggests some practical guidance on how to incorporate past evidence into informative hyper-priors. By combining evidence from past studies and data available, the model parameter estimates can significantly be improved. The effect of prior choice seems to be less important on the hotspot identification. Impact on Industry The results show the benefits of incorporating prior information when working with limited crash data in road safety studies. }
}
@article{Heydari201441,
title = {Bayesian methodology to estimate and update safety performance functions under limited data conditions: A sensitivity analysis },
journal = {Accident Analysis & Prevention },
volume = {64},
number = {0},
pages = {41 - 51},
year = {2014},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2013.11.001},
url = {http://www.sciencedirect.com/science/article/pii/S0001457513004454},
author = {Shahram Heydari and Luis F. Miranda-Moreno and Dominique Lord and Liping Fu},
keywords = {Full Bayes road safety analysis},
keywords = {Prior distribution},
keywords = {\{SPF\} parameter estimation and update},
keywords = {Index of treatment effectiveness },
abstract = {Abstract In road safety studies, decision makers must often cope with limited data conditions. In such circumstances, the maximum likelihood estimation (MLE), which relies on asymptotic theory, is unreliable and prone to bias. Moreover, it has been reported in the literature that (a) Bayesian estimates might be significantly biased when using non-informative prior distributions under limited data conditions, and that (b) the calibration of limited data is plausible when existing evidence in the form of proper priors is introduced into analyses. Although the Highway Safety Manual (2010) (HSM) and other research studies provide calibration and updating procedures, the data requirements can be very taxing. This paper presents a practical and sound Bayesian method to estimate and/or update safety performance function (SPF) parameters combining the information available from limited data with the \{SPF\} parameters reported in the HSM. The proposed Bayesian updating approach has the advantage of requiring fewer observations to get reliable estimates. This paper documents this procedure. The adopted technique is validated by conducting a sensitivity analysis through an extensive simulation study with 15 different models, which include various prior combinations. This sensitivity analysis contributes to our understanding of the comparative aspects of a large number of prior distributions. Furthermore, the proposed method contributes to unification of the Bayesian updating process for SPFs. The results demonstrate the accuracy of the developed methodology. Therefore, the suggested approach offers considerable promise as a methodological tool to estimate and/or update baseline \{SPFs\} and to evaluate the efficacy of road safety countermeasures under limited data conditions. }
}
@article{Ye201472,
title = {Comparing three commonly used crash severity models on sample size requirements: Multinomial logit, ordered probit and mixed logit models },
journal = {Analytic Methods in Accident Research },
volume = {1},
number = {0},
pages = {72 - 85},
year = {2014},
note = {},
issn = {2213-6657},
doi = {http://dx.doi.org/10.1016/j.amar.2013.03.001},
url = {http://www.sciencedirect.com/science/article/pii/S221366571300002X},
author = {Fan Ye and Dominique Lord},
keywords = {Sample size},
keywords = {Crash severity model},
keywords = {Multinomial logit model},
keywords = {Ordered probit model},
keywords = {Mixed logit model },
abstract = {Abstract There have been many studies that have documented the application of crash severity models to explore the relationship between accident severity and its contributing factors. Although a large amount of work has been done on different types of models, no research has been conducted about quantifying the sample size requirements for crash severity modeling. Similar to count data models, small data sets could significantly influence model performance. The objective of this study is therefore to examine the effects of sample size on the three most commonly used crash severity models: multinomial logit, ordered probit and mixed logit models. The study objective is accomplished via a Monte-Carlo approach using simulated and observed crash data. The results of this study are consistent with prior expectations in that small sample sizes significantly affect the development of crash severity models, no matter which type is used. Furthermore, among the three models, the mixed logit model requires the largest sample size, while the ordered probit model requires the lowest sample size. The sample size requirement for the multinomial logit model is located between these two models. }
}
@article{Kuo2013138,
title = {Using geographical information systems to organize police patrol routes effectively by grouping hotspots of crash and crime data },
journal = {Journal of Transport Geography },
volume = {30},
number = {0},
pages = {138 - 148},
year = {2013},
note = {},
issn = {0966-6923},
doi = {http://dx.doi.org/10.1016/j.jtrangeo.2013.04.006},
url = {http://www.sciencedirect.com/science/article/pii/S0966692313000707},
author = {Pei-Fen Kuo and Dominique Lord and Troy Duane Walden},
keywords = {Kernel Density},
keywords = {\{DDACTS\}},
keywords = {Hotspots},
keywords = {Cluster pattern},
keywords = {Crash and crime },
abstract = {Abstract Applying Data-Driven Approaches to Crime and Traffic Safety (DDACTS) can help police departments allocate limited resources more efficiently. By focusing on hazardous areas, highly visible traffic law enforcement simultaneously can reduce both crime and crashes. Most studies have focused on the reduction of crime and crashes after applying new patrol routes, but few have documented how to improve or change police dispatch time. The objective of this study was to compare the police dispatch time between two conditions: (1) police patrol routes with organized hotspots, and (2) police patrol route patterns without focusing on hotspots. A secondary objective consisted of developing a procedure to describe the calculation of the change in dispatch time. This study used data obtained from the College Station Police Department. Crime and crash data were collected between January 2005 and September 2010, which included 65,461 offense reports and 14,712 crash reports. The study procedure includes four steps: (1) geocoding the data, (2) defining the hotspots, (3) organizing the best patrol routes, and (4) estimating the effectiveness. ArcGIS was used for the data analysis. The results indicate that using \{DDACTS\} principles can potentially reduce police dispatch time by 13% and 17% when the top five and top ten hotspot routes respectively are included in the analysis. The procedure can be used by law enforcement agencies to estimate whether or not the \{DDACTS\} protocols can be an effective tool for reducing law enforcement dispatch times when crash and crime data are analyzed simultaneously. }
}
@article{Geedipally2012258,
title = {The negative binomial-Lindley generalized linear model: Characteristics and application using crash data },
journal = {Accident Analysis & Prevention },
volume = {45},
number = {0},
pages = {258 - 265},
year = {2012},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2011.07.012},
url = {http://www.sciencedirect.com/science/article/pii/S0001457511001977},
author = {Srinivas Reddy Geedipally and Dominique Lord and Soma Sekhar Dhavala},
keywords = {Poisson-gamma},
keywords = {Negative binomial Lindley},
keywords = {Generalized linear model},
keywords = {Crash data },
abstract = {There has been a considerable amount of work devoted by transportation safety analysts to the development and application of new and innovative models for analyzing crash data. One important characteristic about crash data that has been documented in the literature is related to datasets that contained a large amount of zeros and a long or heavy tail (which creates highly dispersed data). For such datasets, the number of sites where no crash is observed is so large that traditional distributions and regression models, such as the Poisson and Poisson-gamma or negative binomial (NB) models cannot be used efficiently. To overcome this problem, the NB-Lindley (NB-L) distribution has recently been introduced for analyzing count data that are characterized by excess zeros. The objective of this paper is to document the application of a \{NB\} generalized linear model with Lindley mixed effects (NB-L GLM) for analyzing traffic crash data. The study objective was accomplished using simulated and observed datasets. The simulated dataset was used to show the general performance of the model. The model was then applied to two datasets based on observed data. One of the dataset was characterized by a large amount of zeros. The NB-L \{GLM\} was compared with the \{NB\} and zero-inflated models. Overall, the research study shows that the NB-L \{GLM\} not only offers superior performance over the \{NB\} and zero-inflated models when datasets are characterized by a large number of zeros and a long tail, but also when the crash dataset is highly dispersed. }
}
@article{Lord20111738,
title = {The negative binomial–Lindley distribution as a tool for analyzing crash data characterized by a large amount of zeros },
journal = {Accident Analysis & Prevention },
volume = {43},
number = {5},
pages = {1738 - 1742},
year = {2011},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2011.04.004},
url = {http://www.sciencedirect.com/science/article/pii/S0001457511000856},
author = {Dominique Lord and Srinivas Reddy Geedipally},
keywords = {Count data},
keywords = {Safety},
keywords = {Negative binomial distribution},
keywords = {Poisson distribution},
keywords = {Negative binomial–Lindley distribution },
abstract = {The modeling of crash count data is a very important topic in highway safety. As documented in the literature, given the characteristics associated with crash data, transportation safety analysts have proposed a significant number of analysis tools, statistical methods and models for analyzing such data. Among the data issues, we find the one related to crash data which have a large amount of zeros and a long or heavy tail. It has been found that using this kind of dataset could lead to erroneous results or conclusions if the wrong statistical tools or methods are used. Thus, the purpose of this paper is to introduce a new distribution, known as the negative binomial–Lindley (NB-L), which has very recently been introduced for analyzing data characterized by a large number of zeros. The NB–L offers the advantage of being able to handle this kind of datasets, while still maintaining similar characteristics as the traditional negative binomial (NB). In other words, the NB–L is a two-parameter distribution and the long-term mean is never equal to zero. To examine this distribution, simulated and observed data were used. The results show that the NB–L can provide a better statistical fit than the traditional \{NB\} for datasets that contain a large amount of zeros. }
}
@article{Zou20131042,
title = {Application of finite mixture of negative binomial regression models with varying weight parameters for vehicle crash data analysis },
journal = {Accident Analysis & Prevention },
volume = {50},
number = {0},
pages = {1042 - 1051},
year = {2013},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2012.08.004},
url = {http://www.sciencedirect.com/science/article/pii/S0001457512002916},
author = {Yajie Zou and Yunlong Zhang and Dominique Lord},
keywords = {Negative binomial},
keywords = {Finite mixture model},
keywords = {Dispersion},
keywords = {Weight parameter},
keywords = {Crash data },
abstract = {Recently, a finite mixture of negative binomial (NB) regression models has been proposed to address the unobserved heterogeneity problem in vehicle crash data. This approach can provide useful information about features of the population under study. For a standard finite mixture of regression models, previous studies have used a fixed weight parameter that is applied to the entire dataset. However, various studies suggest modeling the weight parameter as a function of the explanatory variables in the data. The objective of this study is to investigate the differences on the modeling and fitting results between the two-component finite mixture of \{NB\} regression models with fixed weight parameters (FMNB-2) and the two-component finite mixture of \{NB\} regression models with varying weight parameters (GFMNB-2), and compare the group classification from both models. To accomplish the objective of this study, the FMNB-2 and GFMNB-2 models are applied to two crash datasets. The important findings can be summarized as follows: first, the GFMNB-2 models can provide more reasonable classification results, as well as better statistical fitting performance than the FMNB-2 models; second, the GFMNB-2 models can be used to better reveal the source of dispersion observed in the crash data than the FMNB-2 models. Therefore, it is concluded that in many cases the GFMNB-2 models may be a better alternative to the FMNB-2 models for explaining the heterogeneity and the nature of the dispersion in the crash data. }
}
@article{VieiraGomes20121732,
title = {Estimating the safety performance of urban intersections in Lisbon, Portugal },
journal = {Safety Science },
volume = {50},
number = {9},
pages = {1732 - 1739},
year = {2012},
note = {},
issn = {0925-7535},
doi = {http://dx.doi.org/10.1016/j.ssci.2012.03.022},
url = {http://www.sciencedirect.com/science/article/pii/S0925753512000860},
author = {Sandra Vieira Gomes and Srinivas Reddy Geedipally and Dominique Lord},
keywords = {Crash prediction models},
keywords = {Generalized linear modeling},
keywords = {Road accidents},
keywords = {Urban intersections},
keywords = {Lisbon },
abstract = {According to official statistics, a large percentage of crashes in Portugal are reported on urban roads. For instance, from 2004 to 2007, about 70% of all injury accidents and 43% of the fatalities occurred inside urban agglomerations. This important safety problem has also been observed on the urban network of Lisbon. Understanding this significant problem, the Government of the Portuguese Republic via its research grant agency – The Foundation for Science and Technology – funded a project whose primary objective consists of developing tools that would help estimating the safety performance of various components of the urban highway system in Lisbon. This paper documents one component of the safety tools that were developed and describes the steps that were taken to develop predictive models for estimating the safety performance of signalized and unsignalized intersections of Lisbon. Several crash predictive models were developed using the Poisson-gamma modeling framework. Two types of models were estimated: flow-only and models with covariates. They were estimated using crash and other related data collected at 44 three-legged and 50 four-legged intersections for the years 2004–2007, inclusively. It was found that some highway geometric design characteristics were associated with the crashes occurring at urban three- and four-legged intersections in Lisbon. }
}
@article{Kuo2013256,
title = {Accounting for site-selection bias in before–after studies for continuous distributions: Characteristics and application using speed data },
journal = {Transportation Research Part A: Policy and Practice },
volume = {49},
number = {0},
pages = {256 - 269},
year = {2013},
note = {},
issn = {0965-8564},
doi = {http://dx.doi.org/10.1016/j.tra.2013.01.023},
url = {http://www.sciencedirect.com/science/article/pii/S096585641300030X},
author = {Pei-Fen Kuo and Dominique Lord},
keywords = {Before–after study},
keywords = {\{ANCOVA\}},
keywords = {Site selection bias},
keywords = {Policy},
keywords = {Normal distribution},
keywords = {Vehicle speed},
keywords = {Regression-to-the-mean },
abstract = {The before–after study is still the most popular method used by traffic engineers and transportation safety analysts for evaluating the effects of an intervention. Compared to the cross-sectional study, the before–after study has lower within-subject variability since it directly accounts for changes that have occurred at the study sites. However, although this kind of study may offer superior performance, it can still be plagued by important methodological limitations, which could significantly alter the study outcome. They include the regression-to-the-mean (RTM) and site-selection effects. The primary objective of this study consists of presenting a method that can reduce the selection effects when an entry criterion is used in before–after studies for continuous data (e.g. speed, reaction times, etc.), without relying on the use of a control group. The distribution of the data could follow a normal or lognormal distribution. The study objective was accomplished using simulated and observed speed data collected in Florida. The proposed method documented in this paper was compared to the Naïve, Control Group (CG) and the Analysis of Covariance (ANCOVA) methods. The simulation results show that the proposed method provides a more precise estimate than the Naïve method, as expected. In addition, the method performs better than the \{CG\} and the \{ANCOVA\} methods when similar control group data are not available. The results also show that higher entry criteria, lower between-subject variances, and higher within-subject variances cause higher selection biases. When traffic engineers and urban planners evaluate or compare different strategies, the proposed method can be applied to adjust naïve estimators of treatment effectiveness documented in previous studies without similar control group data. }
}
@article{Lord201252,
title = {Examining the effects of site selection criteria for evaluating the effectiveness of traffic safety countermeasures },
journal = {Accident Analysis & Prevention },
volume = {47},
number = {0},
pages = {52 - 63},
year = {2012},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2011.12.008},
url = {http://www.sciencedirect.com/science/article/pii/S0001457511003368},
author = {Dominique Lord and Pei-Fen Kuo},
keywords = {Regression-to-the-mean},
keywords = {Biased estimate},
keywords = {Safety index},
keywords = {Site selection effects},
keywords = {Before–after study},
keywords = {Empirical Bayes method },
abstract = {The primary objective of this paper is to describe how site selection effects can influence the safety effectiveness of treatments. More specifically, the goal is to quantify the bias for the safety effectiveness of a treatment as a function of different entry criteria as well as other factors associated with crash data, and propose a new method to minimize this bias when a control group is not available. The study objective was accomplished using simulated data. The proposed method documented in this paper was compared to the four most common types of before–after studies: the Naïve, using a control group (CG), the empirical Bayes (EB) method based on the method of moment (EBMM), and the \{EB\} method based on a control group (EBCG). Five scenarios were examined: a direct comparison of the methods, different dispersion parameter values of the Negative Binomial model, different sample sizes, different values of the index of safety effectiveness ( θ ), and different levels of uncertainty associated with the index. Based on the simulated scenarios (also supported theoretically), the study results showed that higher entry criteria, larger values of the safety effectiveness, and smaller dispersion parameter values will cause a larger selection bias. Furthermore, among all methods evaluated, the Naïve and the \{EBMM\} methods are both significantly affected by the selection bias. Using a control group, or the EBCG, can mutually eliminate the site selection bias, as long as the characteristics of the control group (truncated data for the \{CG\} method or the non-truncated sample population for the \{EBCG\} method) are exactly the same as for the treatment group. In practice, finding datasets for the control group with the exact same characteristics as for the treatment group may not always be feasible. To overcome this problem, the method proposed in this study can be used to adjust the Naïve estimator of the index of safety effectiveness, even when the mean and dispersion parameter are not properly estimated. }
}
@article{Patil2012646,
title = {Analysis of crash severities using nested logit model—Accounting for the underreporting of crashes },
journal = {Accident Analysis & Prevention },
volume = {45},
number = {0},
pages = {646 - 653},
year = {2012},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2011.09.034},
url = {http://www.sciencedirect.com/science/article/pii/S0001457511002715},
author = {Sunil Patil and Srinivas Reddy Geedipally and Dominique Lord},
keywords = {Crash injury severity},
keywords = {Nested logit},
keywords = {Underreporting },
abstract = {Recent studies in the area of highway safety have demonstrated the usefulness of logit models for modeling crash injury severities. Use of these models enables one to identify and quantify the effects of factors that contribute to certain levels of severity. Most often, these models are estimated assuming equal probability of the occurrence for each injury severity level in the data. However, traffic crash data are generally characterized by underreporting, especially when crashes result in lower injury severity. Thus, the sample used for an analysis is often outcome-based, which can result in a biased estimation of model parameters. This is more of a problem when a nested logit model specification is used instead of a multinomial logit model and when true shares of the outcomes-injury severity levels in the population are not known (which is almost always the case). This study demonstrates an application of a recently proposed weighted conditional maximum likelihood estimator in tackling the problem of underreporting of crashes when using a nested logit model for crash severity analyses. }
}
@article{Lord200753,
title = {Further notes on the application of zero-inflated models in highway safety },
journal = {Accident Analysis & Prevention },
volume = {39},
number = {1},
pages = {53 - 57},
year = {2007},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2006.06.004},
url = {http://www.sciencedirect.com/science/article/pii/S0001457506001072},
author = {Dominique Lord and Simon Washington and John N. Ivan},
keywords = {Zero-inflated models},
keywords = {Statistical models},
keywords = {Poisson},
keywords = {Negative binomial},
keywords = {Statistical methods },
abstract = {The intent of this note is to succinctly articulate additional points that were not provided in the original paper (Lord et al., 2005) and to help clarify a collective reluctance to adopt zero-inflated (ZI) models for modeling highway safety data. A dialogue on this important issue, just one of many important safety modeling issues, is healthy discourse on the path towards improved safety modeling. This note first provides a summary of prior findings and conclusions of the original paper. It then presents two critical and relevant issues: the maximizing statistical fit fallacy and logic problems with the \{ZI\} model in highway safety modeling. Finally, we provide brief conclusions. }
}
@article{Geedipally20101273,
title = {Investigating the effect of modeling single-vehicle and multi-vehicle crashes separately on confidence intervals of Poisson–gamma models },
journal = {Accident Analysis & Prevention },
volume = {42},
number = {4},
pages = {1273 - 1282},
year = {2010},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2010.02.004},
url = {http://www.sciencedirect.com/science/article/pii/S0001457510000497},
author = {Srinivas Reddy Geedipally and Dominique Lord},
keywords = {Single-vehicle crashes},
keywords = {Multi-vehicle crashes},
keywords = {Confidence intervals },
abstract = {Crash prediction models still constitute one of the primary tools for estimating traffic safety. These statistical models play a vital role in various types of safety studies. With a few exceptions, they have often been employed to estimate the number of crashes per unit of time for an entire highway segment or intersection, without distinguishing the influence different sub-groups have on crash risk. The two most important sub-groups that have been identified in the literature are single- and multi-vehicle crashes. Recently, some researchers have noted that developing two distinct models for these two categories of crashes provides better predicting performance than developing models combining both crash categories together. Thus, there is a need to determine whether a significant difference exists for the computation of confidence intervals when a single model is applied rather than two distinct models for single- and multi-vehicle crashes. Building confidence intervals have many important applications in highway safety. This paper investigates the effect of modeling single- and multi-vehicle (head-on and rear-end only) crashes separately versus modeling them together on the prediction of confidence intervals of Poisson–gamma models. Confidence intervals were calculated for total (all severities) crash models and fatal and severe injury crash models. The data used for the comparison analysis were collected on Texas multilane undivided highways for the years 1997–2001. This study shows that modeling single- and multi-vehicle crashes separately predicts larger confidence intervals than modeling them together as a single model. This difference is much larger for fatal and injury crash models than for models for all severity levels. Furthermore, it is found that the single- and multi-vehicle crashes are not independent. Thus, a joint (bivariate) model which accounts for correlation between single- and multi-vehicle crashes is developed and it predicts wider confidence intervals than a univariate model for all severities. Finally, the simulation results show that separate models predict values that are closer to the true confidence intervals, and thus this research supports previous studies that recommended modeling single- and multi-vehicle crashes separately for analyzing highway segments. }
}
@article{Lord20081013,
title = {Methodology for estimating the variance and confidence intervals for the estimate of the product of baseline models and \{AMFs\} },
journal = {Accident Analysis & Prevention },
volume = {40},
number = {3},
pages = {1013 - 1017},
year = {2008},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2007.11.008},
url = {http://www.sciencedirect.com/science/article/pii/S0001457507002047},
author = {Dominique Lord},
keywords = {Crash prediction models},
keywords = {Baseline models},
keywords = {Variance estimation},
keywords = {Confidence intervals},
keywords = {Highway Safety Manual },
abstract = {This manuscript describes a methodology for estimating the variance and 95% confidence intervals (CI) for the estimate of the product between baseline models and Accident Modification Factors (AMFs). This methodology is provided for the upcoming Highway Safety Manual (HSM) currently in development in the United States (U.S.). The methodology is separated into two parts. The first part covers the proposed approach for estimating the variance of the estimate of the product between baseline models and AMFs. The second part presents the method for estimating the variance of baseline models. Several examples are presented to illustrate the application of the methodology. }
}
@article{Lord20081441,
title = {Investigating the effects of the fixed and varying dispersion parameters of Poisson-gamma models on empirical Bayes estimates },
journal = {Accident Analysis & Prevention },
volume = {40},
number = {4},
pages = {1441 - 1457},
year = {2008},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2008.03.014},
url = {http://www.sciencedirect.com/science/article/pii/S0001457508000481},
author = {Dominique Lord and Peter Young-Jin Park},
keywords = {Crash prediction models},
keywords = {Dispersion parameter},
keywords = {Empirical Bayes estimates},
keywords = {Negative binomial},
keywords = {Rural intersections },
abstract = {Traditionally, transportation safety analysts have used the empirical Bayes (EB) method to improve the estimate of the long-term mean of individual sites; to correct for the regression-to-the-mean (RTM) bias in before–after studies; and to identify hotspots or high risk locations. The \{EB\} method combines two different sources of information: (1) the expected number of crashes estimated via crash prediction models, and (2) the observed number of crashes at individual sites. Crash prediction models have traditionally been estimated using a negative binomial (NB) (or Poisson-gamma) modeling framework due to the over-dispersion commonly found in crash data. A weight factor is used to assign the relative influence of each source of information on the \{EB\} estimate. This factor is estimated using the mean and variance functions of the \{NB\} model. With recent trends that illustrated the dispersion parameter to be dependent upon the covariates of \{NB\} models, especially for traffic flow-only models, as well as varying as a function of different time-periods, there is a need to determine how these models may affect \{EB\} estimates. The objectives of this study are to examine how commonly used functional forms as well as fixed and time-varying dispersion parameters affect the \{EB\} estimates. To accomplish the study objectives, several traffic flow-only crash prediction models were estimated using a sample of rural three-legged intersections located in California. Two types of aggregated and time-specific models were produced: (1) the traditional \{NB\} model with a fixed dispersion parameter and (2) the generalized \{NB\} model (GNB) with a time-varying dispersion parameter, which is also dependent upon the covariates of the model. Several statistical methods were used to compare the fitting performance of the various functional forms. The results of the study show that the selection of the functional form of \{NB\} models has an important effect on \{EB\} estimates both in terms of estimated values, weight factors, and dispersion parameters. Time-specific models with a varying dispersion parameter provide better statistical performance in terms of goodness-of-fit (GOF) than aggregated multi-year models. Furthermore, the identification of hazardous sites, using the \{EB\} method, can be significantly affected when a \{GNB\} model with a time-varying dispersion parameter is used. Thus, erroneously selecting a functional form may lead to select the wrong sites for treatment. The study concludes that transportation safety analysts should not automatically use an existing functional form for modeling motor vehicle crashes without conducting rigorous analyses to estimate the most appropriate functional form linking crashes with traffic flow. }
}
@article{Lord2008751,
title = {Effects of low sample mean values and small sample size on the estimation of the fixed dispersion parameter of Poisson-gamma models for modeling motor vehicle crashes: A Bayesian perspective },
journal = {Safety Science },
volume = {46},
number = {5},
pages = {751 - 770},
year = {2008},
note = {},
issn = {0925-7535},
doi = {http://dx.doi.org/10.1016/j.ssci.2007.03.005},
url = {http://www.sciencedirect.com/science/article/pii/S0925753507000355},
author = {Dominique Lord and Luis F. Miranda-Moreno},
keywords = {Poisson-gamma},
keywords = {Poisson-lognormal},
keywords = {Highway safety},
keywords = {Small sample size},
keywords = {Low sample mean },
abstract = {There has been considerable research conducted on the development of statistical models for predicting motor vehicle crashes on highway facilities. Over the last few years, there has been a significant increase in the application hierarchical Bayes methods for modeling motor vehicle crash data. Whether the inferences are estimated using classical or Bayesian methods, the most common probabilistic structure used for modeling this type of data remains the traditional Poisson-gamma (or Negative Binomial) model. Crash data collected for highway safety studies often have the unusual attributes of being characterized by low sample mean values and, due to the prohibitive costs of collecting data, small sample sizes. Previous studies have shown that the dispersion parameter of Poisson-gamma models can be seriously mis-estimated when the models are estimated using the maximum likelihood estimation (MLE) method for these extreme conditions. Despite important work done on this topic for the MLE, nobody has so far examined how low sample mean values and small sample sizes affect the posterior mean of the dispersion parameter of Poisson-gamma models estimated using the hierarchical Bayes method. The inverse dispersion parameter plays an important role in various types of highway safety studies. It is therefore vital to determine the conditions in which the inverse dispersion parameter may be mis-estimated for this category of models. To accomplish the objectives of this study, a simulation framework is developed to generate data from the Poisson-gamma distributions using different values describing the mean, the dispersion parameter, the sample size, and the prior specification. Vague and non-vague prior specifications are tested for determining the magnitude of the biases introduced by low sample mean values and small sample sizes. A series of datasets are also simulated from the Poisson-lognormal distributions, in the light of recent work done by statisticians on this mixed distribution. The study shows that a dataset characterized by a low sample mean combined with a small sample size can seriously affect the estimation of the posterior mean of the dispersion parameter when a vague prior specification is used to characterize the gamma hyper-parameter. The risk of a mis-estimated posterior mean can be greatly minimized when an appropriate non-vague prior distribution is used. Finally, the study shows that Poisson-lognormal models are recommended over Poisson-gamma models when assuming vague priors and whenever crash data characterized by low sample mean values are used for developing crash prediction models. }
}
@article{Lord20081123,
title = {Application of the Conway–Maxwell–Poisson generalized linear model for analyzing motor vehicle crashes },
journal = {Accident Analysis & Prevention },
volume = {40},
number = {3},
pages = {1123 - 1134},
year = {2008},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2007.12.003},
url = {http://www.sciencedirect.com/science/article/pii/S0001457507002163},
author = {Dominique Lord and Seth D. Guikema and Srinivas Reddy Geedipally},
keywords = {Statistical models},
keywords = {Conway–Maxwell–Poisson distribution},
keywords = {Negative binomial},
keywords = {Regression models},
keywords = {Bayesian models },
abstract = {This paper documents the application of the Conway–Maxwell–Poisson (COM-Poisson) generalized linear model (GLM) for modeling motor vehicle crashes. The COM-Poisson distribution, originally developed in 1962, has recently been re-introduced by statisticians for analyzing count data subjected to over- and under-dispersion. This innovative distribution is an extension of the Poisson distribution. The objectives of this study were to evaluate the application of the COM-Poisson \{GLM\} for analyzing motor vehicle crashes and compare the results with the traditional negative binomial (NB) model. The comparison analysis was carried out using the most common functional forms employed by transportation safety analysts, which link crashes to the entering flows at intersections or on segments. To accomplish the objectives of the study, several \{NB\} and COM-Poisson \{GLMs\} were developed and compared using two datasets. The first dataset contained crash data collected at signalized four-legged intersections in Toronto, Ont. The second dataset included data collected for rural four-lane divided and undivided highways in Texas. Several methods were used to assess the statistical fit and predictive performance of the models. The results of this study show that COM-Poisson \{GLMs\} perform as well as \{NB\} models in terms of \{GOF\} statistics and predictive performance. Given the fact the COM-Poisson distribution can also handle under-dispersed data (while the \{NB\} distribution cannot or has difficulties converging), which have sometimes been observed in crash databases, the COM-Poisson \{GLM\} offers a better alternative over the \{NB\} model for modeling motor vehicle crashes, especially given the important limitations recently documented in the safety literature about the latter type of model. }
}
@article{Park2009683,
title = {Application of finite mixture models for vehicle crash data analysis },
journal = {Accident Analysis & Prevention },
volume = {41},
number = {4},
pages = {683 - 691},
year = {2009},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2009.03.007},
url = {http://www.sciencedirect.com/science/article/pii/S0001457509000542},
author = {Byung-Jung Park and Dominique Lord},
keywords = {Highway safety},
keywords = {Over-dispersion},
keywords = {Finite mixture},
keywords = {Negative binomial regression model},
keywords = {Latent class model },
abstract = {Developing sound or reliable statistical models for analyzing motor vehicle crashes is very important in highway safety studies. However, a significant difficulty associated with the model development is related to the fact that crash data often exhibit over-dispersion. Sources of dispersion can be varied and are usually unknown to the transportation analysts. These sources could potentially affect the development of negative binomial (NB) regression models, which are often the model of choice in highway safety. To help in this endeavor, this paper documents an alternative formulation that could be used for capturing heterogeneity in crash count models through the use of finite mixture regression models. The finite mixtures of Poisson or \{NB\} regression models are especially useful where count data were drawn from heterogeneous populations. These models can help determine sub-populations or groups in the data among others. To evaluate these models, Poisson and \{NB\} mixture models were estimated using data collected in Toronto, Ontario. These models were compared to standard \{NB\} regression model estimated using the same data. The results of this study show that the dataset seemed to be generated from two distinct sub-populations, each having different regression coefficients and degrees of over-dispersion. Although over-dispersion in crash data can be dealt with in a variety of ways, the mixture model can help provide the nature of the over-dispersion in the data. It is therefore recommended that transportation safety analysts use this type of model before the traditional \{NB\} model, especially when the data are suspected to belong to different groups. }
}
@article{Li20081611,
title = {Predicting motor vehicle crashes using Support Vector Machine models },
journal = {Accident Analysis & Prevention },
volume = {40},
number = {4},
pages = {1611 - 1618},
year = {2008},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2008.04.010},
url = {http://www.sciencedirect.com/science/article/pii/S0001457508000808},
author = {Xiugang Li and Dominique Lord and Yunlong Zhang and Yuanchang Xie},
keywords = {Highway},
keywords = {Crash},
keywords = {Support Vector Machine},
keywords = {Negative binomial model},
keywords = {Neural network },
abstract = {Crash prediction models have been very popular in highway safety analyses. However, in highway safety research, the prediction of outcomes is seldom, if ever, the only research objective when estimating crash prediction models. Only very few existing methods can be used to efficiently predict motor vehicle crashes. Thus, there is a need to examine new methods for better predicting motor vehicle crashes. The objective of this study is to evaluate the application of Support Vector Machine (SVM) models for predicting motor vehicle crashes. \{SVM\} models, which are based on the statistical learning theory, are a new class of models that can be used for predicting values. To accomplish the objective of this study, Negative Binomial (NB) regression and \{SVM\} models were developed and compared using data collected on rural frontage roads in Texas. Several models were estimated using different sample sizes. The study shows that \{SVM\} models predict crash data more effectively and accurately than traditional \{NB\} models. In addition, \{SVM\} models do not over-fit the data and offer similar, if not better, performance than Back-Propagation Neural Network (BPNN) models documented in previous research. Given this characteristic and the fact that \{SVM\} models are faster to implement than \{BPNN\} models, it is suggested to use these models if the sole purpose of the study consists of predicting motor vehicle crashes. }
}
@article{Xie2007922,
title = {Predicting motor vehicle collisions using Bayesian neural network models: An empirical analysis },
journal = {Accident Analysis & Prevention },
volume = {39},
number = {5},
pages = {922 - 933},
year = {2007},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2006.12.014},
url = {http://www.sciencedirect.com/science/article/pii/S0001457507000073},
author = {Yuanchang Xie and Dominique Lord and Yunlong Zhang},
keywords = {Artificial neural networks},
keywords = {Bayesian methods},
keywords = {Negative binomial},
keywords = {Statistical model},
keywords = {Frontage roads },
abstract = {Statistical models have frequently been used in highway safety studies. They can be utilized for various purposes, including establishing relationships between variables, screening covariates and predicting values. Generalized linear models (GLM) and hierarchical Bayes models (HBM) have been the most common types of model favored by transportation safety analysts. Over the last few years, researchers have proposed the back-propagation neural network (BPNN) model for modeling the phenomenon under study. Compared to \{GLMs\} and HBMs, \{BPNNs\} have received much less attention in highway safety modeling. The reasons are attributed to the complexity for estimating this kind of model as well as the problem related to “over-fitting” the data. To circumvent the latter problem, some statisticians have proposed the use of Bayesian neural network (BNN) models. These models have been shown to perform better than \{BPNN\} models while at the same time reducing the difficulty associated with over-fitting the data. The objective of this study is to evaluate the application of \{BNN\} models for predicting motor vehicle crashes. To accomplish this objective, a series of models was estimated using data collected on rural frontage roads in Texas. Three types of models were compared: BPNN, \{BNN\} and the negative binomial (NB) regression models. The results of this study show that in general both types of neural network models perform better than the \{NB\} regression model in terms of data prediction. Although the \{BPNN\} model can occasionally provide better or approximately equivalent prediction performance compared to the \{BNN\} model, in most cases its prediction performance is worse than the \{BNN\} model. In addition, the data fitting performance of the \{BPNN\} model is consistently worse than the \{BNN\} model, which suggests that the \{BNN\} model has better generalization abilities than the \{BPNN\} model and can effectively alleviate the over-fitting problem without significantly compromising the nonlinear approximation ability. The results also show that \{BNNs\} could be used for other useful analyses in highway safety, including the development of accident modification factors and for improving the prediction capabilities for evaluating different highway design alternatives. }
}
@article{Park2010741,
title = {Bias properties of Bayesian statistics in finite mixture of negative binomial regression models in crash data analysis },
journal = {Accident Analysis & Prevention },
volume = {42},
number = {2},
pages = {741 - 749},
year = {2010},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2009.11.002},
url = {http://www.sciencedirect.com/science/article/pii/S0001457509003030},
author = {Byung-Jung Park and Dominique Lord and Jeffrey D. Hart},
keywords = {Bias},
keywords = {Bayesian summary statistics},
keywords = {Heterogeneity},
keywords = {Finite mixture model},
keywords = {Negative binomial },
abstract = {Factors that cause heterogeneity in crash data are often unknown to researchers and failure to accommodate such heterogeneity in statistical models can undermine the validity of empirical results. A recently proposed finite mixture for the negative binomial regression model has shown a potential advantage in addressing the unobserved heterogeneity as well as providing useful information about features of the population under study. Despite its usefulness, however, no study has been found to examine the performance of this finite mixture under various conditions of sample sizes and sample-mean values that are common in crash data analysis. This study investigated the bias associated with the Bayesian summary statistics (posterior mean and median) of dispersion parameters in the two-component finite mixture of negative binomial regression models. A simulation study was conducted using various sample sizes under different sample-mean values. Two prior specifications (non-informative and weakly-informative) on the dispersion parameter were also compared. The results showed that the posterior mean using the non-informative prior exhibited a high bias for the dispersion parameter and should be avoided when the dataset contains less than 2,000 observations (even for high sample-mean values). The posterior median showed much better bias properties, particularly at small sample sizes and small sample means. However, as the sample size increases, the posterior median using the non-informative prior also began to exhibit an upward-bias trend. In such cases, the posterior mean or median with the weakly-informative prior provided smaller bias. Based on simulation results, guidelines about the choice of priors and the summary statistics to use are presented for different sample sizes and sample-mean values. }
}
@article{Lord2007427,
title = {A strategy to reduce older driver injuries at intersections using more accommodating roundabout design practices },
journal = {Accident Analysis & Prevention },
volume = {39},
number = {3},
pages = {427 - 432},
year = {2007},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2006.09.011},
url = {http://www.sciencedirect.com/science/article/pii/S0001457506001710},
author = {Dominique Lord and Ida van Schalkwyk and Susan Chrysler and Loren Staplin},
keywords = {Older driver},
keywords = {Intersection},
keywords = {Roundabout},
keywords = {Safety},
keywords = {Engineering countermeasure },
abstract = {This paper briefly summarizes a laboratory study investigating strategies designed to improve the ability of our most vulnerable drivers, the elderly, to safely negotiate the most dangerous and demanding of all traffic situations – intersections – through increased use of modern roundabouts. Compared to conventional intersections, roundabouts have demonstrated the potential to significantly reduce the most injurious (angle) type of crashes and slow the operating speed of all vehicles, while maintaining a high capacity for moving traffic through an intersection. This research sought to develop and evaluate countermeasures with the potential to improve the perceived comfort, confidence, and/or safety of seniors in using roundabouts. Research methods included focus groups and structured interviews utilizing photographs, which had been edited to include novel traffic control devices. The results suggest that design elements that improve the path guidance for older drivers are necessary to encourage roundabout use by this group. Recommendations for improved practice related to advance warning signs, guide signs, yield treatments, directional signs, and exit treatments are presented. }
}
@article{Ye2009257,
title = {Estimating the variance in before-after studies },
journal = {Journal of Safety Research },
volume = {40},
number = {4},
pages = {257 - 263},
year = {2009},
note = {},
issn = {0022-4375},
doi = {http://dx.doi.org/10.1016/j.jsr.2009.04.004},
url = {http://www.sciencedirect.com/science/article/pii/S0022437509000644},
author = {Zhirui Ye and Dominique Lord},
keywords = {Before-after study},
keywords = {Variance estimation},
keywords = {Bootstrap},
keywords = {Resampling},
keywords = {Non-parametric },
abstract = {Problem To simplify the computation of the variance in before-after studies, it is generally assumed that the observed crash data for each entity (or observation) are Poisson distributed. Given the characteristics of this distribution, the observed value (xi) for each entity is implicitly made equal to its variance. However, the variance should be estimated using the conditional properties of this observed value (defined as a random variable), that is, f(xi|μi), since the mean of the observed value is in fact unknown. Method Parametric and non-parametric bootstrap methods were investigated to evaluate the conditional assumption using simulated and observed data. Results The results of this study show that observed data should not be used as a substitute for the variance, even if the entities are assumed to be Poisson distributed. Consequently, the estimated variance for the parameters under study in traditional before-after studies is likely to be underestimated. Conclusions The proposed methods offer more accurate approaches for estimating the variance in before-after studies. }
}
@article{Ye2011290,
title = {Safety impact of Gateway Monuments },
journal = {Accident Analysis & Prevention },
volume = {43},
number = {1},
pages = {290 - 300},
year = {2011},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2010.08.027},
url = {http://www.sciencedirect.com/science/article/pii/S0001457510002605},
author = {Zhirui Ye and David Veneziano and Dominique Lord},
keywords = {Traffic safety},
keywords = {Gateway Monuments},
keywords = {Empirical Bayes},
keywords = {Before–after study },
abstract = {Gateway Monuments are free standing roadside structures or signage that communicate the name of a city, country or township to motorists. The placement of such monuments within state-controlled right-of-way is a relatively recent occurrence in California. As a result, the California Department of Transportation (Caltrans) initiated research to quantify the impacts that this type of signage may or may not have on crashes in their vicinity. To date, no specific research has examined the impact such features have on crashes. To determine whether these features impacted safety, the before–after study method using the Empirical Bayes technique was used, with reference groups and Safety Performance Functions adapted from existing studies, eliminating the need to calibrate new models. Results indicated that, on an individual basis, no deterioration in safety was observed at any monument site. When all sites were examined collectively (using two different scenarios), the calculated index of effectiveness values were 0.978 and 0.680, respectively, corresponding to 2.2% and 32.0% reductions in crashes. In addition to the \{EB\} method, naïve study methods (with and without \{AADT\} taken into account) were applied to the study data. Results (crash reductions) from these methods also showed that the presence of Gateway Monuments did not have negative impact on traffic safety. However, the use of \{EB\} technique should be very careful employed when adopting reference groups from different jurisdictions, as these may affect the validity of \{EB\} results. In light of these results, Caltrans may continue to participate in the Gateway Monument Program at its discretion with the knowledge that roadway safety is not impacted by monuments. }
}
@article{Park2010662,
title = {Bayesian mixture modeling approach to account for heterogeneity in speed data },
journal = {Transportation Research Part B: Methodological },
volume = {44},
number = {5},
pages = {662 - 673},
year = {2010},
note = {Bayesian Methods },
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/j.trb.2010.02.004},
url = {http://www.sciencedirect.com/science/article/pii/S0191261510000196},
author = {Byung-Jung Park and Yunlong Zhang and Dominique Lord},
keywords = {Speed distribution},
keywords = {Heterogeneity},
keywords = {Skewness},
keywords = {Multimodality},
keywords = {Finite mixture},
keywords = {Bayesian estimation },
abstract = {Speed is one of the most important parameters describing the condition of the traffic flow. Many analytical models related to traffic flow either produce speed as a performance measure, or use speed to determine other measures such as travel time, delay, and the level of service. Mathematical models or distributions used to describe speed characteristics are very useful, especially when they are utilized in the context of simulation and theoretical derivations. Traditionally, normal, log–normal and composite distributions have been the usual mathematical distributions to characterize speed data. These traditional distributions, however, often fail to produce an adequate goodness-of-fit when the empirical distribution of speed data exhibits bimodality (or multimodality), skewness, or excess kurtosis (peakness). This often occurs when the speed data are generated from several different sub-populations, for example, mixed traffic flow conditions or mixed vehicle compositions. The traditional modeling approach also lacks the ability to explain the underlying factors that lead to different speed distribution curves. The objective of this paper is to explore the applicability of the finite mixture of normal (Gaussian) distributions to capture the heterogeneity in vehicle speed data, and thereby explaining the aforementioned special characteristics. For the parameter estimation, Bayesian estimation method via Markov Chain Monte Carlo (MCMC) sampling is adopted. The field data collected on IH-35 in Texas is used to evaluate the proposed models. The results of this study show that the finite mixture of normal distributions can very effectively describe the heterogeneous speed data, and provide richer information usually not available from the traditional models. The finite mixture modeling produces an excellent fit to the multimodal speed distribution curve. Moreover, the causes of different speed distributions can be identified through investigating the components. }
}
@article{Boivin2009374,
title = {Antiproliferative and antioxidant activities of common vegetables: A comparative study },
journal = {Food Chemistry },
volume = {112},
number = {2},
pages = {374 - 380},
year = {2009},
note = {},
issn = {0308-8146},
doi = {http://dx.doi.org/10.1016/j.foodchem.2008.05.084},
url = {http://www.sciencedirect.com/science/article/pii/S0308814608006419},
author = {Dominique Boivin and Sylvie Lamy and Simon Lord-Dufour and Jessica Jackson and Edith Beaulieu and Martine Côté and Albert Moghrabi and Stéphane Barrette and Denis Gingras and Richard Béliveau},
keywords = {Cancer prevention},
keywords = {Cruciferous vegetables},
keywords = {Allium vegetables},
keywords = {Antioxidants },
abstract = {Epidemiological studies have consistently linked abundant consumption of fruits and vegetables to a reduction of the risk of developing several types of cancer. In most cases, however, the identification of specific fruits and vegetables that are responsible for these effects is still lacking, retarding the implementation of effective dietary-based chemopreventive approaches. As a first step towards the identification of foods endowed with the most potent chemopreventive activities, we evaluated the inhibitory effects of extracts isolated from 34 vegetables on the proliferation of 8 different tumour cell lines. The extracts from cruciferous vegetables as well as those from vegetables of the genus Allium inhibited the proliferation of all tested cancer cell lines whereas extracts from vegetables most commonly consumed in Western countries were much less effective. The antiproliferative effect of vegetables was specific to cells of cancerous origin and was found to be largely independent of their antioxidant properties. These results thus indicate that vegetables have very different inhibitory activities towards cancer cells and that the inclusion of cruciferous and Allium vegetables in the diet is essential for effective dietary-based chemopreventive strategies. }
}
@article{Lord2006422,
title = {Erratum to “Modeling crash-flow-density and crash-flow-V/C ratio relationships for rural and urban freeway segments” [Accid. Anal. Prev. 37 (2005) 185–199] },
journal = {Accident Analysis & Prevention },
volume = {38},
number = {2},
pages = {422 - 423},
year = {2006},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2005.10.011},
url = {http://www.sciencedirect.com/science/article/pii/S000145750500182X},
author = {Dominique Lord and Abdelaziz Manar and Anna Vizioli}
}
@article{Lord2006751,
title = {Modeling motor vehicle crashes using Poisson-gamma models: Examining the effects of low sample mean values and small sample size on the estimation of the fixed dispersion parameter },
journal = {Accident Analysis & Prevention },
volume = {38},
number = {4},
pages = {751 - 766},
year = {2006},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2006.02.001},
url = {http://www.sciencedirect.com/science/article/pii/S0001457506000169},
author = {Dominique Lord},
keywords = {Statistical models},
keywords = {Poisson-gamma},
keywords = {Low sample mean values},
keywords = {Empirical Bayes},
keywords = {Small sample size },
abstract = {There has been considerable research conducted on the development of statistical models for predicting crashes on highway facilities. Despite numerous advancements made for improving the estimation tools of statistical models, the most common probabilistic structure used for modeling motor vehicle crashes remains the traditional Poisson and Poisson-gamma (or Negative Binomial) distribution; when crash data exhibit over-dispersion, the Poisson-gamma model is usually the model of choice most favored by transportation safety modelers. Crash data collected for safety studies often have the unusual attributes of being characterized by low sample mean values. Studies have shown that the goodness-of-fit of statistical models produced from such datasets can be significantly affected. This issue has been defined as the “low mean problem” (LMP). Despite recent developments on methods to circumvent the \{LMP\} and test the goodness-of-fit of models developed using such datasets, no work has so far examined how the \{LMP\} affects the fixed dispersion parameter of Poisson-gamma models used for modeling motor vehicle crashes. The dispersion parameter plays an important role in many types of safety studies and should, therefore, be reliably estimated. The primary objective of this research project was to verify whether the \{LMP\} affects the estimation of the dispersion parameter and, if it is, to determine the magnitude of the problem. The secondary objective consisted of determining the effects of an unreliably estimated dispersion parameter on common analyses performed in highway safety studies. To accomplish the objectives of the study, a series of Poisson-gamma distributions were simulated using different values describing the mean, the dispersion parameter, and the sample size. Three estimators commonly used by transportation safety modelers for estimating the dispersion parameter of Poisson-gamma models were evaluated: the method of moments, the weighted regression, and the maximum likelihood method. In an attempt to complement the outcome of the simulation study, Poisson-gamma models were fitted to crash data collected in Toronto, Ont. characterized by a low sample mean and small sample size. The study shows that a low sample mean combined with a small sample size can seriously affect the estimation of the dispersion parameter, no matter which estimator is used within the estimation process. The probability the dispersion parameter becomes unreliably estimated increases significantly as the sample mean and sample size decrease. Consequently, the results show that an unreliably estimated dispersion parameter can significantly undermine empirical Bayes (EB) estimates as well as the estimation of confidence intervals for the gamma mean and predicted response. The paper ends with recommendations about minimizing the likelihood of producing Poisson-gamma models with an unreliable dispersion parameter for modeling motor vehicle crashes. }
}
@article{Lord200535,
title = {Poisson, Poisson-gamma and zero-inflated regression models of motor vehicle crashes: balancing statistical fit and theory },
journal = {Accident Analysis & Prevention },
volume = {37},
number = {1},
pages = {35 - 46},
year = {2005},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2004.02.004},
url = {http://www.sciencedirect.com/science/article/pii/S0001457504000521},
author = {Dominique Lord and Simon P. Washington and John N. Ivan},
keywords = {Zero-inflated models},
keywords = {Poisson distribution},
keywords = {Negative binomial distribution},
keywords = {Bernoulli trials},
keywords = {Safety performance functions},
keywords = {Small area analysis },
abstract = {There has been considerable research conducted over the last 20 years focused on predicting motor vehicle crashes on transportation facilities. The range of statistical models commonly applied includes binomial, Poisson, Poisson-gamma (or negative binomial), zero-inflated Poisson and negative binomial models (ZIP and ZINB), and multinomial probability models. Given the range of possible modeling approaches and the host of assumptions with each modeling approach, making an intelligent choice for modeling motor vehicle crash data is difficult. There is little discussion in the literature comparing different statistical modeling approaches, identifying which statistical models are most appropriate for modeling crash data, and providing a strong justification from basic crash principles. In the recent literature, it has been suggested that the motor vehicle crash process can successfully be modeled by assuming a dual-state data-generating process, which implies that entities (e.g., intersections, road segments, pedestrian crossings, etc.) exist in one of two states—perfectly safe and unsafe. As a result, the \{ZIP\} and \{ZINB\} are two models that have been applied to account for the preponderance of “excess” zeros frequently observed in crash count data. The objective of this study is to provide defensible guidance on how to appropriate model crash data. We first examine the motor vehicle crash process using theoretical principles and a basic understanding of the crash process. It is shown that the fundamental crash process follows a Bernoulli trial with unequal probability of independent events, also known as Poisson trials. We examine the evolution of statistical models as they apply to the motor vehicle crash process, and indicate how well they statistically approximate the crash process. We also present the theory behind dual-state process count models, and note why they have become popular for modeling crash data. A simulation experiment is then conducted to demonstrate how crash data give rise to “excess” zeros frequently observed in crash data. It is shown that the Poisson and other mixed probabilistic structures are approximations assumed for modeling the motor vehicle crash process. Furthermore, it is demonstrated that under certain (fairly common) circumstances excess zeros are observed—and that these circumstances arise from low exposure and/or inappropriate selection of time/space scales and not an underlying dual state process. In conclusion, carefully selecting the time/space scales for analysis, including an improved set of explanatory variables and/or unobserved heterogeneity effects in count regression models, or applying small-area statistical methods (observations with low exposure) represent the most defensible modeling approaches for datasets with a preponderance of zeros. }
}
@article{Lord2004609,
title = {Estimating the safety performance of urban road transportation networks },
journal = {Accident Analysis & Prevention },
volume = {36},
number = {4},
pages = {609 - 620},
year = {2004},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/S0001-4575(03)00069-1},
url = {http://www.sciencedirect.com/science/article/pii/S0001457503000691},
author = {Dominique Lord and Bhagwant N. Persaud},
keywords = {Safety},
keywords = {Crash prediction models},
keywords = {Safety performance functions},
keywords = {Urban network},
keywords = {Transportation planning },
abstract = {Transportation planning models are typically used to estimate future traffic patterns, peak period traffic, travel time, and various environmental or other related traffic flow characteristics. Unfortunately, traffic safety is seldom, if ever, explicitly considered proactively during the transportation planning process. This omission is attributed to various factors, including the lack of available tools needed to estimate the number of crashes during this process. To help fill this void, the research on which this paper is based aimed, as a primary objective, to develop a tool that would allow the estimation of crashes on digital or coded urban transportation networks during the planning process. The secondary objective of the research was to describe how the predictive models should be applied on these networks and explain the important issues and limitations surrounding their application. To accomplish these objectives, safety performance functions specifically created for this work were applied to two sample digital networks created with the help of EMME/2, a software package widely used in transportation planning. The results showed that it is possible to predict crashes on digital transportation networks, but confirmed the reality that the accuracy of the predictions is directly related to the precision of the traffic flow estimates. The crash predictions are also sensitive to how the digital network is coded, and it is shown how appropriate adjustments can be made. }
}
@article{Lord2005185,
title = {Modeling crash-flow-density and crash-flow-V/C ratio relationships for rural and urban freeway segments },
journal = {Accident Analysis & Prevention },
volume = {37},
number = {1},
pages = {185 - 199},
year = {2005},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2004.07.003},
url = {http://www.sciencedirect.com/science/article/pii/S0001457504000703},
author = {Dominique Lord and Abdelaziz Manar and Anna Vizioli},
keywords = {Predictive models},
keywords = {Crashes},
keywords = {Safety},
keywords = {Freeways},
keywords = {Density},
keywords = {Hourly volumes},
keywords = {Capacity},
keywords = {V/C ratio },
abstract = {There has been considerable research conducted in recent years into establishing relationships between crashes and various traffic flow characteristics for freeway segments. Most of the research has focused on determining the relationship between crashes and highway traffic volumes, while little attention has been focused on the relationships of vehicle density, level of service (LOS), vehicle occupancy, V/C ratio and speed distribution. Despite overall progress, there is still no clear understanding about the effects of different traffic flow characteristics on safety. In fact, several studies reviewed in this work were found to have methodological limitations. These include using predictive models with a normal error structure, aggregated crash rates, and inadequate functional forms for the data at hand. The original research on which this paper is based is aimed to determine the statistical relationship using commonly applied predictive models (i.e., functional forms) between crashes and hourly traffic flow characteristics, such as traffic volume, vehicle density and V/C ratios, for rural and urban freeway segments respectively. To accomplish this objective, predictive models have been developed from data collected on freeway segments located in downtown and outside of Montreal, Quebec. Three different functional forms are evaluated. The results show that predictive models that use traffic volume as the only explanatory variable may not adequately characterize the accident process on freeway segments. Functional forms that incorporate density and V/C ratio offer a richer description of crashes occurring on these facilities, whether they are located in a rural or urban environment. Finally, separate predictive models for single- and multi-vehicle crashes should be developed rather than one common model for all crash types. }
}
@comment{{Fred Mannering PAPERS}}
@article{Behnood201456,
title = {Latent class analysis of the effects of age, gender, and alcohol consumption on driver-injury severities },
journal = {Analytic Methods in Accident Research },
volume = {3–4},
number = {0},
pages = {56 - 91},
year = {2014},
note = {},
issn = {2213-6657},
doi = {http://dx.doi.org/10.1016/j.amar.2014.10.001},
url = {http://www.sciencedirect.com/science/article/pii/S2213665714000256},
author = {Ali Behnood and Arash M. Roshandeh and Fred L. Mannering},
keywords = {Latent class multinomial logit model},
keywords = {Single-vehicle crashes},
keywords = {Driver-injury severity},
keywords = {Alcohol consumption },
abstract = {Abstract This study explores the differences in driver-injury severity between drivers impaired and not-alcohol-impaired, while taking into consideration the role of age and gender. Using data from single-vehicle crashes from Illinois' Cook County over an eight-year period from January 1, 2004 to December 31, 2011, separate alcohol-impaired and not-alcohol-impaired models of driver-injury severity (with possible outcomes of no injury, minor injury, and severe injury) were estimated for younger male, older male, younger female, and older female drivers (those younger than 31 years old were considered younger drivers, and those 31 years old and older were considered older drivers). In addition to considering driver age, alcohol condition, and gender, a wide range of variables potentially affecting crash severity was considered, including a number of variables relating to highway attributes, vehicle characteristics, and environmental conditions. Using a latent class multinomial logit modeling approach to capture unobserved heterogeneity, estimation results show that there were substantial differences across age/gender groups in the absence/presence of alcohol. In addition, among others, particularly complex relationships were uncovered with regard to the impact of alcohol consumption, safety-belt effectiveness, roadway type, distracted driving, vehicle occupancy, and the effects of airbag deployment on injury severity. }
}
@article{Winston2014158,
title = {Implementing technology to improve public highway performance: A leapfrog technology from the private sector is going to be necessary },
journal = {Economics of Transportation },
volume = {3},
number = {2},
pages = {158 - 165},
year = {2014},
note = {Special Issue in Honor of Herbert Mohring },
issn = {2212-0122},
doi = {http://dx.doi.org/10.1016/j.ecotra.2013.12.004},
url = {http://www.sciencedirect.com/science/article/pii/S2212012213000270},
author = {Clifford Winston and Fred Mannering},
keywords = {Highways},
keywords = {Optimal pricing and investment},
keywords = {Technology},
keywords = {Driverless cars },
abstract = {Abstract Policymakers could implement available, well-tested technologies to improve the efficiency of highway pricing, investment, and operations, which would improve travel speeds, reliability, and safety and reduce highway expenditures. Unfortunately, political and bureaucratic impediments to implement such technology exist and are unlikely to be overcome in the near future. However, technological innovations underway in the private sector, especially the driverless car, are likely to eventually leapfrog the technology that the public highway authorities could and should implement and will enable road users to obtain most of the potential benefits from technological advances in highway travel. }
}
@article{Xiong2014109,
title = {The analysis of vehicle crash injury-severity data: A Markov switching approach with road-segment heterogeneity },
journal = {Transportation Research Part B: Methodological },
volume = {67},
number = {0},
pages = {109 - 128},
year = {2014},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/j.trb.2014.04.007},
url = {http://www.sciencedirect.com/science/article/pii/S0191261514000630},
author = {Yingge Xiong and Justin L. Tobias and Fred L. Mannering},
keywords = {Markov switching models},
keywords = {Random parameter models},
keywords = {Ordered response model},
keywords = {Data augmentation},
keywords = {Markov Chain Monte Carlo simulation },
abstract = {Abstract Time-constant assumptions in discrete-response heterogeneity models can often be violated. To address this, a time-varying heterogeneity approach to model unobserved heterogeneity in ordered response data is considered. A Markov switching random parameters structure (which accounts for heterogeneity across observations) is proposed to accommodate both time-varying and time-constant (cross-sectional) unobserved heterogeneity in an ordered discrete-response probability model. A data augmented Markov Chain Monte Carlo algorithm for non-linear model estimation is developed to facilitate model estimation. The performance of the cross-sectional heterogeneity model and time-varying heterogeneity model are examined with vehicle crash-injury severity data. The time-varying heterogeneity model (Markov switching random parameters ordered probit) is found to provide the best overall model fit. Two roadway safety states are shown to exist and roadway segments transition between these two states according to Markov transition probabilities. The results demonstrate considerable promise for Markov switching models in a wide variety of applications. }
}
@article{Wu201390,
title = {Safety impacts of signal-warning flashers and speed control at high-speed signalized intersections },
journal = {Accident Analysis & Prevention },
volume = {54},
number = {0},
pages = {90 - 98},
year = {2013},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2013.01.016},
url = {http://www.sciencedirect.com/science/article/pii/S0001457513000298},
author = {Zifeng Wu and Anuj Sharma and Fred L. Mannering and Shefang Wang},
keywords = {Speed limit reduction},
keywords = {Crash frequency},
keywords = {Crash severity},
keywords = {Nested logit model},
keywords = {Random parameter negative binomial model},
keywords = {High-speed signalized intersection},
keywords = {Signal-warning flashers },
abstract = {For many years, to reduce the crash frequency and severity at high-speed signalized intersections, warning flashers have been used to alert drivers of potential traffic-signal changes. Recently, more aggressive countermeasures at such intersections include a speed-limit reduction in addition to warning flashers. While such speed-control strategies have the potential to further improve the crash-mitigation effectiveness of warning flashers, a rigorous statistical analysis of crash data from such intersections has not been undertaken to date. This paper uses 10-year crash data from 28 intersections in Nebraska (all with intersection approaches having signal-warning flashers; some with no speed-limit reduction, and the others with either 5 mi/h or 10 mi/h reduction in speed limit) to estimate a random parameters negative binomial model of crash frequency and a nested logit model of crash-injury severity. The estimation findings show that, while a wide variety of factors significantly influence the frequency and severity of crashes, the effect of the 5 mi/h speed-limit reduction is ambiguous—decreasing the frequency of crashes on some intersection approaches and increasing it on others, and decreasing some crash-injury severities and increasing others. In contrast, the 10 mi/h reduction in speed limit unambiguously decreased both the frequency and injury-severity of crashes. It is speculated that, in the presence of potentially heterogeneous driver responses to decreased speed limits, the smaller distances covered during reaction time at lower speeds (allowing a higher likelihood of crash avoidance) and the reduced energy of crashes associated with lower speed limits are not necessarily sufficient to unambiguously decrease the frequency and severity of crashes when the speed-limit reduction is just 5 mi/h. However, they are sufficient to unambiguously decrease the frequency and severity of crashes when the speed-limit reduction is 10 mi/h. Based on this research, speed-limit reductions in conjunction with signal-warning flashers appear to be an effective safety countermeasure, but only clearly so if the speed-limit reduction is at least 10 mi/h. }
}
@article{Mannering20141,
title = {Analytic methods in accident research: Methodological frontier and future directions },
journal = {Analytic Methods in Accident Research },
volume = {1},
number = {0},
pages = {1 - 22},
year = {2014},
note = {},
issn = {2213-6657},
doi = {http://dx.doi.org/10.1016/j.amar.2013.09.001},
url = {http://www.sciencedirect.com/science/article/pii/S2213665713000031},
author = {Fred L. Mannering and Chandra R. Bhat},
keywords = {Highway safety},
keywords = {Crash frequency},
keywords = {Crash severity},
keywords = {Econometric methods},
keywords = {Statistical methods},
keywords = {Accident analysis },
abstract = {Abstract The analysis of highway-crash data has long been used as a basis for influencing highway and vehicle designs, as well as directing and implementing a wide variety of regulatory policies aimed at improving safety. And, over time there has been a steady improvement in statistical methodologies that have enabled safety researchers to extract more information from crash databases to guide a wide array of safety design and policy improvements. In spite of the progress made over the years, important methodological barriers remain in the statistical analysis of crash data and this, along with the availability of many new data sources, present safety researchers with formidable future challenges, but also exciting future opportunities. This paper provides guidance in defining these challenges and opportunities by first reviewing the evolution of methodological applications and available data in highway-accident research. Based on this review, fruitful directions for future methodological developments are identified and the role that new data sources will play in defining these directions is discussed. It is shown that new methodologies that address complex issues relating to unobserved heterogeneity, endogeneity, risk compensation, spatial and temporal correlations, and more, have the potential to significantly expand our understanding of the many factors that affect the likelihood and severity (in terms of personal injury) of highway crashes. This in turn can lead to more effective safety countermeasures that can substantially reduce highway-related injuries and fatalities. }
}
@article{Hainen201332,
title = {A hazard-based analysis of airport security transit times },
journal = {Journal of Air Transport Management },
volume = {32},
number = {0},
pages = {32 - 38},
year = {2013},
note = {},
issn = {0969-6997},
doi = {http://dx.doi.org/10.1016/j.jairtraman.2013.06.002},
url = {http://www.sciencedirect.com/science/article/pii/S096969971300063X},
author = {Alexander M. Hainen and Stephen M. Remias and Darcy M. Bullock and Fred L. Mannering},
keywords = {Airport security},
keywords = {Transit time},
keywords = {Duration model },
abstract = {Abstract Airport security screening, and the amount of time it costs travelers, has been a persistent concern to travelers, airport authorities, and airlines – particularly in recent years where changes in perceived threats have resulted in changes in security procedures that have caused great uncertainty relating to security transit times. To gain a better understanding of the factors influencing travelers' security transit times, determinants of security transit times are studied by using anonymous Bluetooth media access control address matching to determine the actual security travel times of individual passengers at the Cincinnati/Northern Kentucky International Airport. These transit-time data are then analyzed using a random-parameters hazard-based duration model to statistically explore the factors that affect airport security transit times. The estimation results reveal, as expected, that a wide variety of factors affect security transit times including the number of enplaning seats (reflecting flight schedules), weather conditions, day of week, as well as obvious variables such as traveler volume and the number of open security lanes. The detailed statistical findings show that current security procedures are reactive instead of proactive, and that substantial reductions in security transit times could be attained by optimizing security operations using a statistical model such as the one estimated in this paper. }
}
@article{Kang201310,
title = {Statistical analysis of pedestrian perceptions of sidewalk level of service in the presence of bicycles },
journal = {Transportation Research Part A: Policy and Practice },
volume = {53},
number = {0},
pages = {10 - 21},
year = {2013},
note = {},
issn = {0965-8564},
doi = {http://dx.doi.org/10.1016/j.tra.2013.05.002},
url = {http://www.sciencedirect.com/science/article/pii/S0965856413001080},
author = {Lei Kang and Yingge Xiong and Fred L. Mannering},
keywords = {Pedestrian level of service},
keywords = {Pedestrian attitudes},
keywords = {Bicycles},
keywords = {Random parameters ordered probit },
abstract = {Abstract Gaining a better understanding of pedestrian perceptions of level of service (LOS) in urban areas can be useful in developing strategies for providing a comfortable and safe walking environment. Using a sample of 114 respondents, this research studies how pedestrians perceive \{LOS\} on sidewalks shared with bicycles under various urban-street conditions. To do this, 15 carefully constructed video clips of Chinese urban sidewalks are presented to respondents and, after each 60-s video clip, respondents were asked to assess the pedestrian level of service in the video on a scale from \{LOS\} A (the most comfortable pedestrian environment) to \{LOS\} F (the least comfortable pedestrian environment). By estimating random parameters ordered probability models of respondents’ \{LOS\} assessments (to account for unobserved heterogeneity across respondents) we found, as expected, that pedestrian perceptions of \{LOS\} are strongly influenced by the pedestrian flow rate. However, many other factors were found to significantly affect \{LOS\} perceptions including sidewalk width, the presence of a barrier separating the sidewalk from motor-vehicle traffic, the presence of parking next to the sidewalk, the presence of businesses along the sidewalk, the bicycle flow rate, the speed of bicyclist, whether or not bicycles were riding against the flow of pedestrians, weather conditions, time of day, and age of the respondent. The specific impacts of the wide variety of factors that affect pedestrian perceptions of \{LOS\} suggest that a number of important tradeoffs need to be considered when planning pedestrian facilities. }
}
@article{Anastasopoulos2012110,
title = {A multivariate tobit analysis of highway accident-injury-severity rates },
journal = {Accident Analysis & Prevention },
volume = {45},
number = {0},
pages = {110 - 119},
year = {2012},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2011.11.006},
url = {http://www.sciencedirect.com/science/article/pii/S0001457511003095},
author = {Panagiotis Ch. Anastasopoulos and Venky N. Shankar and John E. Haddock and Fred L. Mannering},
keywords = {Accident-injury-severity rates},
keywords = {Censoring},
keywords = {Contemporaneous error correlation},
keywords = {Multivariate tobit regression},
keywords = {Roadway geometrics},
keywords = {Interstate highways },
abstract = {Relatively recent research has illustrated the potential that tobit regression has in studying factors that affect vehicle accident rates (accidents per distance traveled) on specific roadway segments. Tobit regression has been used because accident rates on specific roadway segments are continuous data that are left-censored at zero (they are censored because accidents may not be observed on all roadway segments during the period over which data are collected). This censoring may arise from a number of sources, one of which being the possibility that less severe crashes may be under-reported and thus may be less likely to appear in crash databases. Traditional tobit-regression analyses have dealt with the overall accident rate (all crashes regardless of injury severity), so the issue of censoring by the severity of crashes has not been addressed. However, a tobit-regression approach that considers accident rates by injury-severity level, such as the rate of no-injury, possible injury and injury accidents per distance traveled (as opposed to all accidents regardless of injury-severity), can potentially provide new insights, and address the possibility that censoring may vary by crash-injury severity. Using five-year data from highways in Washington State, this paper estimates a multivariate tobit model of accident-injury-severity rates that addresses the possibility of differential censoring across injury-severity levels, while also accounting for the possible contemporaneous error correlation resulting from commonly shared unobserved characteristics across roadway segments. The empirical results show that the multivariate tobit model outperforms its univariate counterpart, is practically equivalent to the multivariate negative binomial model, and has the potential to provide a fuller understanding of the factors determining accident-injury-severity rates on specific roadway segments. }
}
@article{Morgan20111852,
title = {The effects of road-surface conditions, age, and gender on driver-injury severities },
journal = {Accident Analysis & Prevention },
volume = {43},
number = {5},
pages = {1852 - 1863},
year = {2011},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2011.04.024},
url = {http://www.sciencedirect.com/science/article/pii/S0001457511001059},
author = {Abigail Morgan and Fred L. Mannering},
keywords = {Gender differences},
keywords = {Age differences},
keywords = {Crash-injury severities},
keywords = {Mixed logit model},
keywords = {Weather},
keywords = {Road-surface conditions },
abstract = {Drivers’ adaptation to weather-induced changes in roadway-surface conditions is a complex process that can potentially be influenced by many factors including age and gender. Using a mixed logit analysis, this research assesses the effects that age, gender, and other factors have on crash severities by considering single-vehicle crashes that occurred on dry, wet, and snow/ice-covered roadway surfaces. With an extensive database of single-vehicle crashes from Indiana in 2007 and 2008, estimation results showed that there were substantial differences across age/gender groups under different roadway-surface conditions. For example, for all females and older males, the likelihood of severe injuries increased when crashes occurred on wet or snow/ice surfaces–but for male drivers under 45 years of age, the probability of severe injuries decreased on wet and snow/ice surfaces – relative to dry-surface crashes. This and many other significant differences among age and gender groups suggest that drivers perceive and react to pavement-surface conditions in very different ways, and this has important safety implications. Furthermore, the empirical findings of this study highlight the value of considering subsets of data to unravel the complex relationships within crash-injury severity analysis. }
}
@article{Anastasopoulos2012628,
title = {A study of factors affecting highway accident rates using the random-parameters tobit model },
journal = {Accident Analysis & Prevention },
volume = {45},
number = {0},
pages = {628 - 633},
year = {2012},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2011.09.015},
url = {http://www.sciencedirect.com/science/article/pii/S0001457511002521},
author = {Panagiotis Ch. Anastasopoulos and Fred L. Mannering and Venky N. Shankar and John E. Haddock},
keywords = {Accident rates},
keywords = {Random parameters},
keywords = {Tobit regression},
keywords = {Pavement condition},
keywords = {Roadway geometrics},
keywords = {Interstate highways },
abstract = {A large body of previous literature has used a variety of count-data modeling techniques to study factors that affect the frequency of highway accidents over some time period on roadway segments of a specified length. An alternative approach to this problem views vehicle accident rates (accidents per mile driven) directly instead of their frequencies. Viewing the problem as continuous data instead of count data creates a problem in that roadway segments that do not have any observed accidents over the identified time period create continuous data that are left-censored at zero. Past research has appropriately applied a tobit regression model to address this censoring problem, but this research has been limited in accounting for unobserved heterogeneity because it has been assumed that the parameter estimates are fixed over roadway-segment observations. Using 9-year data from urban interstates in Indiana, this paper employs a random-parameters tobit regression to account for unobserved heterogeneity in the study of motor-vehicle accident rates. The empirical results show that the random-parameters tobit model outperforms its fixed-parameters counterpart and has the potential to provide a fuller understanding of the factors determining accident rates on specific roadway segments. }
}
@article{Anastasopoulos20111140,
title = {An empirical assessment of fixed and random parameter logit models using crash- and non-crash-specific injury data },
journal = {Accident Analysis & Prevention },
volume = {43},
number = {3},
pages = {1140 - 1147},
year = {2011},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2010.12.024},
url = {http://www.sciencedirect.com/science/article/pii/S000145751000401X},
author = {Panagiotis Ch. Anastasopoulos and Fred L. Mannering},
keywords = {Crash-injury severities},
keywords = {Random parameters logit model},
keywords = {Mixed logit model},
keywords = {Pavement condition},
keywords = {Roadway geometrics },
abstract = {Traditional crash-severity modeling uses detailed data gathered after a crash has occurred (number of vehicles involved, age of occupants, weather conditions at the time of the crash, types of vehicles involved, crash type, occupant restraint use, airbag deployment, etc.) to predict the level of occupant injury. However, for prediction purposes, the use of such detailed data makes assessing the impact of alternate safety countermeasures exceedingly difficult due to the large number of variables that need to be known. Using 5-year data from interstate highways in Indiana, this study explores fixed and random parameter statistical models using detailed crash-specific data and data that include the injury outcome of the crash but not other detailed crash-specific data (only more general data are used such as roadway geometrics, pavement condition and general weather and traffic characteristics). The analysis shows that, while models that do not use detailed crash-specific data do not perform as well as those that do, random parameter models using less detailed data still can provide a reasonable level of accuracy. }
}
@article{Savolainen20111666,
title = {The statistical analysis of highway crash-injury severities: A review and assessment of methodological alternatives },
journal = {Accident Analysis & Prevention },
volume = {43},
number = {5},
pages = {1666 - 1676},
year = {2011},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2011.03.025},
url = {http://www.sciencedirect.com/science/article/pii/S0001457511000765},
author = {Peter T. Savolainen and Fred L. Mannering and Dominique Lord and Mohammed A. Quddus},
keywords = {Injury severity},
keywords = {Crash severity},
keywords = {Discrete outcome},
keywords = {Logit},
keywords = {Probit },
abstract = {Reducing the severity of injuries resulting from motor-vehicle crashes has long been a primary emphasis of highway agencies and motor-vehicle manufacturers. While progress can be simply measured by the reduction in injury levels over time, insights into the effectiveness of injury-reduction technologies, policies, and regulations require a more detailed empirical assessment of the complex interactions that vehicle, roadway, and human factors have on resulting crash-injury severities. Over the years, researchers have used a wide range of methodological tools to assess the impact of such factors on disaggregate-level injury-severity data, and recent methodological advances have enabled the development of sophisticated models capable of more precisely determining the influence of these factors. This paper summarizes the evolution of research and current thinking as it relates to the statistical analysis of motor-vehicle injury severities, and provides a discussion of future methodological directions. }
}
@article{Xiong201339,
title = {The heterogeneous effects of guardian supervision on adolescent driver-injury severities: A finite-mixture random-parameters approach },
journal = {Transportation Research Part B: Methodological },
volume = {49},
number = {0},
pages = {39 - 54},
year = {2013},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/j.trb.2013.01.002},
url = {http://www.sciencedirect.com/science/article/pii/S0191261513000131},
author = {Yingge Xiong and Fred L. Mannering},
keywords = {Adolescent crashes},
keywords = {Graduated driver licensing},
keywords = {Heterogeneity model},
keywords = {Gaussian mixture},
keywords = {Bayesian inference},
keywords = {Permutation sampler },
abstract = {One of the key aspects of graduated driver licensing programs is the new-driver experience gained in the presence of a guardian (a person providing mandatory supervision from the passenger seat). However, the effect that this guardian-supervising practice has on adolescent drivers’ crash-injury severity (should a crash occur) is not well understood. This paper seeks to provide insights into the injury-prevention effectiveness of guardian supervision by developing an appropriate econometric structure to account for the complex interactions that are likely to occur in the study of the heterogeneous effects of guardian supervision on crash-injury severities. As opposed to conventional heterogeneity models with standard distributional assumptions, this paper deals with the heterogeneous effects by accounting for the possible multivariate characteristics of parameter distributions in addition to allowing for multimodality, skewness and kurtosis. A Markov Chain Monte Carlo (MCMC) algorithm is developed for estimation and the permutation sampler proposed by Frühwirth-Schnatter (2001) is extended for model identification. The econometric analysis shows the presence of two distinct driving environments (defined by roadway geometric and traffic conditions). Model estimation results show that, in both of these driving environments, the presence of guardian supervision reduces the crash-injury severity, but in interestingly different ways. Based on the findings of this research, a case could easily be made for extending the time-requirement for guardian supervision in current graduated driver license programs. }
}
@article{Lord2010291,
title = {The statistical analysis of crash-frequency data: A review and assessment of methodological alternatives },
journal = {Transportation Research Part A: Policy and Practice },
volume = {44},
number = {5},
pages = {291 - 305},
year = {2010},
note = {},
issn = {0965-8564},
doi = {http://dx.doi.org/10.1016/j.tra.2010.02.001},
url = {http://www.sciencedirect.com/science/article/pii/S0965856410000376},
author = {Dominique Lord and Fred Mannering},
keywords = {Highway safety},
keywords = {Literature review},
keywords = {Regression models},
keywords = {Count-data models},
keywords = {Crash data },
abstract = {Gaining a better understanding of the factors that affect the likelihood of a vehicle crash has been an area of research focus for many decades. However, in the absence of detailed driving data that would help improve the identification of cause and effect relationships with individual vehicle crashes, most researchers have addressed this problem by framing it in terms of understanding the factors that affect the frequency of crashes – the number of crashes occurring in some geographical space (usually a roadway segment or intersection) over some specified time period. This paper provides a detailed review of the key issues associated with crash-frequency data as well as the strengths and weaknesses of the various methodological approaches that researchers have used to address these problems. While the steady march of methodological innovation (including recent applications of random parameter and finite mixture models) has substantially improved our understanding of the factors that affect crash-frequencies, it is the prospect of combining evolving methodologies with far more detailed vehicle crash data that holds the greatest promise for the future. }
}
@article{Malyshkina2009217,
title = {Markov switching negative binomial models: An application to vehicle accident frequencies },
journal = {Accident Analysis & Prevention },
volume = {41},
number = {2},
pages = {217 - 226},
year = {2009},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2008.11.001},
url = {http://www.sciencedirect.com/science/article/pii/S0001457508002170},
author = {Nataliya V. Malyshkina and Fred L. Mannering and Andrew P. Tarko},
keywords = {Accident frequency},
keywords = {Negative binomial},
keywords = {Count data model},
keywords = {Markov switching},
keywords = {Bayesian},
keywords = {\{MCMC\} },
abstract = {In this paper, two-state Markov switching models are proposed to study accident frequencies. These models assume that there are two unobserved states of roadway safety, and that roadway entities (roadway segments) can switch between these states over time. The states are distinct, in the sense that in the different states accident frequencies are generated by separate counting processes (by separate Poisson or negative binomial processes). To demonstrate the applicability of the approach presented herein, two-state Markov switching negative binomial models are estimated using five-year accident frequencies on Indiana interstate highway segments. Bayesian inference methods and Markov Chain Monte Carlo (MCMC) simulations are used for model estimation. The estimated Markov switching models result in a superior statistical fit relative to the standard (single-state) negative binomial model. It is found that the more frequent state is safer and it is correlated with better weather conditions. The less frequent state is found to be less safe and to be correlated with adverse weather conditions. }
}
@article{Savolainen2007955,
title = {Probabilistic models of motorcyclists’ injury severities in single- and multi-vehicle crashes },
journal = {Accident Analysis & Prevention },
volume = {39},
number = {5},
pages = {955 - 963},
year = {2007},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2006.12.016},
url = {http://www.sciencedirect.com/science/article/pii/S0001457507000103},
author = {Peter Savolainen and Fred Mannering},
keywords = {Crash injuries},
keywords = {Motorcycle crashes},
keywords = {Nested logit models},
keywords = {Motorcycle fatalities },
abstract = {Motorcycle fatalities have more than doubled in the United States since 1997—highlighting the need to better understand the many interrelated factors that determine motorcyclists’ crash-injury severities. In this paper, using a detailed crash database from the state of Indiana, we estimate probabilistic models of motorcyclists’ injury severities in single- and multi-vehicle crashes. Nested logit (estimated with full information maximum likelihood) and standard multinomial logit model results show a wide-range of factors significantly influence injury-severity probabilities. Key findings show that increasing motorcyclist age is associated with more severe injuries and that collision type, roadway characteristics, alcohol consumption, helmet use, unsafe speed and other variables play significant roles in crash-injury outcomes. }
}
@article{Malyshkina2009829,
title = {Markov switching multinomial logit model: An application to accident-injury severities },
journal = {Accident Analysis & Prevention },
volume = {41},
number = {4},
pages = {829 - 838},
year = {2009},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2009.04.006},
url = {http://www.sciencedirect.com/science/article/pii/S0001457509000839},
author = {Nataliya V. Malyshkina and Fred L. Mannering},
keywords = {Accident-injury severity},
keywords = {Multinomial logit},
keywords = {Markov switching},
keywords = {Bayesian},
keywords = {\{MCMC\} },
abstract = {In this study, two-state Markov switching multinomial logit models are proposed for statistical modeling of accident-injury severities. These models assume Markov switching over time between two unobserved states of roadway safety as a means of accounting for potential unobserved heterogeneity. The states are distinct in the sense that in different states accident-severity outcomes are generated by separate multinomial logit processes. To demonstrate the applicability of the approach, two-state Markov switching multinomial logit models are estimated for severity outcomes of accidents occurring on Indiana roads over a four-year time period. Bayesian inference methods and Markov Chain Monte Carlo (MCMC) simulations are used for model estimation. The estimated Markov switching models result in a superior statistical fit relative to the standard (single-state) multinomial logit models for a number of roadway classes and accident types. It is found that the more frequent state of roadway safety is correlated with better weather conditions and that the less frequent state is correlated with adverse weather conditions. }
}
@article{Anastasopoulos2009153,
title = {A note on modeling vehicle accident frequencies with random-parameters count models },
journal = {Accident Analysis & Prevention },
volume = {41},
number = {1},
pages = {153 - 159},
year = {2009},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2008.10.005},
url = {http://www.sciencedirect.com/science/article/pii/S0001457508001954},
author = {Panagiotis Ch. Anastasopoulos and Fred L. Mannering},
keywords = {Accident frequency},
keywords = {Count data},
keywords = {Random-parameters Poisson and negative binomial models },
abstract = {In recent years there have been numerous studies that have sought to understand the factors that determine the frequency of accidents on roadway segments over some period of time, using count data models and their variants (negative binomial and zero-inflated models). This study seeks to explore the use of random-parameters count models as another methodological alternative in analyzing accident frequencies. The empirical results show that random-parameters count models have the potential to provide a fuller understanding of the factors determining accident frequencies. }
}
@article{Malyshkina2010122,
title = {Zero-state Markov switching count-data models: An empirical assessment },
journal = {Accident Analysis & Prevention },
volume = {42},
number = {1},
pages = {122 - 130},
year = {2010},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2009.07.012},
url = {http://www.sciencedirect.com/science/article/pii/S0001457509001778},
author = {Nataliya V. Malyshkina and Fred L. Mannering},
keywords = {Accident frequency count-data models},
keywords = {Zero-inflated models},
keywords = {Negative binomial},
keywords = {Markov switching},
keywords = {Bayesian},
keywords = {Markov Chain Monte Carlo (MCMC) },
abstract = {In this study, a two-state Markov switching count-data model is proposed as an alternative to zero-inflated models to account for the preponderance of zeros sometimes observed in transportation count data, such as the number of accidents occurring on a roadway segment over some period of time. For this accident-frequency case, zero-inflated models assume the existence of two states: one of the states is a zero-accident count state, which has accident probabilities that are so low that they cannot be statistically distinguished from zero, and the other state is a normal-count state, in which counts can be non-negative integers that are generated by some counting process, for example, a Poisson or negative binomial. While zero-inflated models have come under some criticism with regard to accident-frequency applications – one fact is undeniable – in many applications they provide a statistically superior fit to the data. The Markov switching approach we propose seeks to overcome some of the criticism associated with the zero-accident state of the zero-inflated model by allowing individual roadway segments to switch between zero and normal-count states over time. An important advantage of this Markov switching approach is that it allows for the direct statistical estimation of the specific roadway-segment state (i.e., zero-accident or normal-count state) whereas traditional zero-inflated models do not. To demonstrate the applicability of this approach, a two-state Markov switching negative binomial model (estimated with Bayesian inference) and standard zero-inflated negative binomial models are estimated using five-year accident frequencies on Indiana interstate highway segments. It is shown that the Markov switching model is a viable alternative and results in a superior statistical fit relative to the zero-inflated models. }
}
@article{Malyshkina2010131,
title = {Empirical assessment of the impact of highway design exceptions on the frequency and severity of vehicle accidents },
journal = {Accident Analysis & Prevention },
volume = {42},
number = {1},
pages = {131 - 139},
year = {2010},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2009.07.013},
url = {http://www.sciencedirect.com/science/article/pii/S000145750900178X},
author = {Nataliya V. Malyshkina and Fred L. Mannering},
keywords = {Design exceptions},
keywords = {Accident frequency},
keywords = {Accident severity},
keywords = {Injury severity },
abstract = {Compliance to standardized highway design criteria is considered essential to ensure roadway safety. However, for a variety of reasons, situations arise where exceptions to standard-design criteria are requested and accepted after review. This research explores the impact that such design exceptions have on the frequency and severity of highway accidents in Indiana. Data on accidents at carefully selected roadway sites with and without design exceptions are used to estimate appropriate statistical models of the frequency and severity of accidents at these sites using recent statistical advances with mixing distributions. The results of the modeling process show that presence of approved design exceptions has not had a statistically significant effect on the average frequency or severity of accidents – suggesting that current procedures for granting design exceptions have been sufficiently rigorous to avoid adverse safety impacts. However, the findings do suggest that the process that determines the frequency of accidents does vary between roadway sites with design exceptions and those without. }
}
@article{Anastasopoulos2008768,
title = {Tobit analysis of vehicle accident rates on interstate highways },
journal = {Accident Analysis & Prevention },
volume = {40},
number = {2},
pages = {768 - 775},
year = {2008},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2007.09.006},
url = {http://www.sciencedirect.com/science/article/pii/S0001457507001674},
author = {Panagiotis Ch. Anastasopoulos and Andrew P. Tarko and Fred L. Mannering},
keywords = {Accident rates},
keywords = {Tobit regression},
keywords = {Pavement condition},
keywords = {Roadway geometrics },
abstract = {There has been an abundance of research that has used Poisson models and its variants (negative binomial and zero-inflated models) to improve our understanding of the factors that affect accident frequencies on roadway segments. This study explores the application of an alternate method, tobit regression, by viewing vehicle accident rates directly (instead of frequencies) as a continuous variable that is left-censored at zero. Using data from vehicle accidents on Indiana interstates, the estimation results show that many factors relating to pavement condition, roadway geometrics and traffic characteristics significantly affect vehicle accident rates. }
}
@article{Milton2008260,
title = {Highway accident severities and the mixed logit model: An exploratory empirical analysis },
journal = {Accident Analysis & Prevention },
volume = {40},
number = {1},
pages = {260 - 266},
year = {2008},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2007.06.006},
url = {http://www.sciencedirect.com/science/article/pii/S0001457507001030},
author = {John C. Milton and Venky N. Shankar and Fred L. Mannering},
keywords = {Mixed logit model},
keywords = {Random parameters},
keywords = {Accident injury severity prediction },
abstract = {Many transportation agencies use accident frequencies, and statistical models of accidents frequencies, as a basis for prioritizing highway safety improvements. However, the use of accident severities in safety programming has been often been limited to the locational assessment of accident fatalities, with little or no emphasis being placed on the full severity distribution of accidents (property damage only, possible injury, injury)—which is needed to fully assess the benefits of competing safety-improvement projects. In this paper we demonstrate a modeling approach that can be used to better understand the injury-severity distributions of accidents on highway segments, and the effect that traffic, highway and weather characteristics have on these distributions. The approach we use allows for the possibility that estimated model parameters can vary randomly across roadway segments to account for unobserved effects potentially relating to roadway characteristics, environmental factors, and driver behavior. Using highway-injury data from Washington State, a mixed (random parameters) logit model is estimated. Estimation findings indicate that volume-related variables such as average daily traffic per lane, average daily truck traffic, truck percentage, interchanges per mile and weather effects such as snowfall are best modeled as random-parameters—while roadway characteristics such as the number of horizontal curves, number of grade breaks per mile and pavement friction are best modeled as fixed parameters. Our results show that the mixed logit model has considerable promise as a methodological tool in highway safety programming. }
}
@article{Niemeier2007365,
title = {Bridging Research and Practice: A Synthesis of Best Practices in Travel Demand Modeling },
journal = {Transportation Research Part A: Policy and Practice },
volume = {41},
number = {5},
pages = {365 - 366},
year = {2007},
note = {Bridging Research and Practice: A Synthesis of Best Practices in Travel Demand Modeling },
issn = {0965-8564},
doi = {http://dx.doi.org/10.1016/j.tra.2006.09.004},
url = {http://www.sciencedirect.com/science/article/pii/S0965856406001133},
author = {Deb Niemeier and Fred Mannering}
}
@article{Mannering200999,
title = {An empirical analysis of driver perceptions of the relationship between speed limits and safety },
journal = {Transportation Research Part F: Traffic Psychology and Behaviour },
volume = {12},
number = {2},
pages = {99 - 106},
year = {2009},
note = {},
issn = {1369-8478},
doi = {http://dx.doi.org/10.1016/j.trf.2008.08.004},
url = {http://www.sciencedirect.com/science/article/pii/S1369847808000752},
author = {Fred Mannering},
keywords = {Speed limits},
keywords = {Safety},
keywords = {Driver Risk Assessment },
abstract = {In recent decades, it has become more common for speed limits to be set for political reasons rather than for safety reasons. As a consequence, the motoring public seems to have increasingly begun questioning the rationality of speed limits. This is evident in observed speed data that show that the majority of drivers routinely exceed posted speed limits. A key motivating factor in drivers’ tendency to exceed the speed limit is that they believe that the excess speed does not threaten safety. This paper, specifically studies this matter by using a survey that asked drivers how fast above the speed limit they feel they can drive before safety is threatened. A probabilistic model is estimated using data gathered from 988 drivers in Indiana. Estimation findings show that drivers’ perception of the speed above the speed limit at which they will receive a speeding ticket is a critical determinant of what they believe is a safe speed – suggesting that enforcement plays an important role in safety perceptions. Other variables found to be significant factors in determining the speed above the speed limit at which safety is first threatened include age, gender, being previously stopped for speeding, and drivers’ ethnicity. }
}
@article{Kim20101751,
title = {A note on modeling pedestrian-injury severity in motor-vehicle crashes with the mixed logit model },
journal = {Accident Analysis & Prevention },
volume = {42},
number = {6},
pages = {1751 - 1758},
year = {2010},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2010.04.016},
url = {http://www.sciencedirect.com/science/article/pii/S0001457510001326},
author = {Joon-Ki Kim and Gudmundur F. Ulfarsson and Venkataraman N. Shankar and Fred L. Mannering},
keywords = {Aging},
keywords = {Gender},
keywords = {Pedestrian},
keywords = {Random parameters},
keywords = {Injury severity },
abstract = {Pedestrian-injury severity has been traditionally modeled with approaches that have assumed that the effect of each variable is fixed across injury observations. This assumption ignores possible unobserved heterogeneity which is likely to be particularly important in pedestrian injuries because unobserved physical health, strength, and behavior may significantly affect the pedestrians’ ability to absorb collision forces. To address such unobserved heterogeneity, this research applies a mixed logit model to analyze pedestrian-injury severity in pedestrian-vehicle crashes. Using police-reported collision data from 1997 through 2000 from North Carolina, several factors were found to more than double the average probability of fatal injury for pedestrians in motor-vehicle crashes including: darkness without streetlights (400% increase in fatality probability), vehicle is a truck (370% increase), freeway (330% increase), speeding involved (360% increase), and collisions involving a motorist who had been drinking (250% increase). It was also found that the effect of pedestrian age was normally distributed across observations, and that as pedestrians became older the probability of fatal injury increased substantially. Heterogeneity in the mean of the random parameters for the freeway and pedestrian-solely-at-fault collision indicators was related to pedestrian gender, and heterogeneity in the mean of the random parameters for the traffic-sign and motorist-back-up indicators was related to pedestrian age. }
}
@article{Gkritza2008443,
title = {Mixed logit analysis of safety-belt use in single- and multi-occupant vehicles },
journal = {Accident Analysis & Prevention },
volume = {40},
number = {2},
pages = {443 - 451},
year = {2008},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2007.07.013},
url = {http://www.sciencedirect.com/science/article/pii/S0001457507001261},
author = {Konstantina Gkritza and Fred L. Mannering},
keywords = {Mixed logit model},
keywords = {Random parameters},
keywords = {Safety-belt use},
keywords = {Passenger safety-belt use },
abstract = {In this paper we demonstrate a modeling approach that can be used to better understand the use of safety belts in single- and multi-occupant vehicles, and the effect that vehicle, roadway and occupant characteristics have on usage rates. Using data from a roadside observational survey of safety-belt use in Indiana, a mixed (random parameters) logit model is estimated. Potentially interrelated choices of safety-belt use by drivers and front-seat passengers are examined. The approach we use also allows for the possibility that estimated model parameters can vary randomly across vehicle occupants to account for unobserved effects potentially relating to roadway characteristics, vehicle attributes, and driver behavior. Estimation findings indicate that the choices of safety-belt use involve a complex interaction of factors and that the effect of these factors can vary significantly across the population. Our results show that the mixed logit model can provide a much fuller understanding of the interaction of the numerous variables which correlate with safety-belt use than traditional discrete-outcome modeling approaches. }
}
@article{Gkritza2011148,
title = {Estimating multimodal transit ridership with a varying fare structure },
journal = {Transportation Research Part A: Policy and Practice },
volume = {45},
number = {2},
pages = {148 - 160},
year = {2011},
note = {},
issn = {0965-8564},
doi = {http://dx.doi.org/10.1016/j.tra.2010.12.005},
url = {http://www.sciencedirect.com/science/article/pii/S0965856410001631},
author = {Konstantina Gkritza and Matthew G. Karlaftis and Fred L. Mannering},
keywords = {Transit demand},
keywords = {Multimodal transit systems},
keywords = {Fare structure},
keywords = {Time-series},
keywords = {High-order serial correlation},
keywords = {Greece },
abstract = {This paper studies public transport demand by estimating a system of equations for multimodal transit systems where different modes may act competitively or cooperatively. Using data from Athens, Greece, we explicitly correct for higher-order serial correlation in the error terms and investigate two, largely overlooked, questions in the transit literature; first, whether a varying fare structure in a multimodal transit system affects demand and, second, what the determinants of ticket versus travelcard sales may be. Model estimation results suggest that the effect of fare type on ridership levels in a multimodal system varies by mode and by relative ticket to travelcard prices. Further, regardless of competition or cooperation between modes, fare increases will have limited effects on ridership, but the magnitude of these effects does depend on the relative ticket to travelcard prices. Finally, incorrectly assuming serial independence for the error terms during model estimation could yield upward or downward biased parameters and hence result in incorrect inferences and policy recommendations. }
}
@article{Lee2002149,
title = {Impact of roadside features on the frequency and severity of run-off-roadway accidents: an empirical analysis },
journal = {Accident Analysis & Prevention },
volume = {34},
number = {2},
pages = {149 - 161},
year = {2002},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/S0001-4575(01)00009-4},
url = {http://www.sciencedirect.com/science/article/pii/S0001457501000094},
author = {Jinsun Lee and Fred Mannering},
keywords = {Run-off-roadway},
keywords = {Countermeasures },
abstract = {In the US, single-vehicle run-off-roadway accidents result in a million highway crashes with roadside features every year and account for approximately one-third of all highway fatalities. Despite the number and severity of run-off-roadway accidents, quantification of the effect of possible countermeasures has been surprisingly limited due to the absence of data (particularly data on roadside features) needed to rigorously analyze factors affecting the frequency and severity of run-off-roadway accidents. This study provides some initial insight into this important problem by combining a number of databases, including a detailed database on roadside features, to analyze run-off-roadway accidents on a 96.6-km section of highway in Washington State. Using zero-inflated count models and nested logit models, statistical models of accident frequency and severity are estimated and the findings isolate a wide range of factors that significantly influence the frequency and severity of run-off-roadway accidents. The marginal effects of these factors are computed to provide an indication on the effectiveness of potential countermeasures. The findings show significant promise in applying new methodological approaches to run-off-roadway accident analysis. }
}
@article{Boyle200457,
title = {Impact of traveler advisory systems on driving speed: some new evidence },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {12},
number = {1},
pages = {57 - 72},
year = {2004},
note = {},
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/j.trc.2003.09.001},
url = {http://www.sciencedirect.com/science/article/pii/S0968090X03000779},
author = {Linda Ng Boyle and Fred Mannering},
keywords = {In-vehicle information systems},
keywords = {Driving simulator},
keywords = {Variable messages },
abstract = {This paper explores the effects of driving behavior using in-vehicle and out-of-vehicle traffic advisory information relating to adverse weather and incident conditions. A full-size, fixed-based driving simulator is used to collect data on drivers’ speed behavior under four different advisory-information conditions: in-vehicle messages, out-of-vehicle messages, both types of messages, and no messages. The findings of this study suggest an interesting phenomenon in that, while messages are significant in reducing speeds in the area of adverse conditions, drivers tend to compensate for this speed reduction by increasing speeds downstream when such adverse conditions do not exist. As a result, the net safety effects of such message systems are ambiguous. }
}
@article{Islam2006267,
title = {Driver aging and its effect on male and female single-vehicle accident injuries: Some additional evidence },
journal = {Journal of Safety Research },
volume = {37},
number = {3},
pages = {267 - 276},
year = {2006},
note = {},
issn = {0022-4375},
doi = {http://dx.doi.org/10.1016/j.jsr.2006.04.003},
url = {http://www.sciencedirect.com/science/article/pii/S0022437506000508},
author = {Samantha Islam and Fred Mannering},
keywords = {Accident injury severity},
keywords = {Gender differences},
keywords = {Age differences },
abstract = {Introduction This study explores the differences in injury severity between male and female drivers, and across the different age groups, in single-vehicle accidents involving passenger cars. Method Given the occurrence of an accident, separate male and female multinomial logit models of injury severity (with possible outcomes of no injury, injury, and fatality) were estimated for young (ages 16 to 24), middle-aged (ages 25 to 64), and older (ages 65 and older) drivers. Results The estimation results show statistically significant differences in the factors that determine injury-severity levels between male and female drivers and among the different driver age groups. Conclusions We discuss a number of plausible explanations for the observed age/gender differences and provide suggestions for future work on the subject. Impact on Industry A better understanding of age and gender differences can lead to improvements in vehicle and highway design to minimize driver injury severity. This paper provides some new evidence to help unravel this complex problem. }
}
@article{Nam200085,
title = {An exploratory hazard-based analysis of highway incident duration },
journal = {Transportation Research Part A: Policy and Practice },
volume = {34},
number = {2},
pages = {85 - 102},
year = {2000},
note = {},
issn = {0965-8564},
doi = {http://dx.doi.org/10.1016/S0965-8564(98)00065-2},
url = {http://www.sciencedirect.com/science/article/pii/S0965856498000652},
author = {Doohee Nam and Fred Mannering},
abstract = {The statistical analysis of highway incident duration has become an increasingly import research topic due to the impact that highway incidents (vehicle accidents and disablements) have on traffic congestion. In addition, there is a growing need to evaluate incident management programs that seek to reduce incident duration and incident-induced traffic congestion. We apply hazard-based duration models to statistically evaluate the time it takes detect/report, respond to, and clear incidents. Two-year data from Washington State's incident response team program were used to estimate the hazard models. The model estimation results show that a wide variety of factors significantly affect incident times (i.e. detection/reporting, response, and clearance times), and that different distributional assumptions for the hazard function are appropriate for the different incident times being considered. It was also found that the estimated coefficients were not stable between the two years of data used in model estimation. The findings of this paper provide an important demonstration of method and an empirical basis to assess incident management programs. }
}
@article{Khorashadi2005910,
title = {Differences in rural and urban driver-injury severities in accidents involving large-trucks: An exploratory analysis },
journal = {Accident Analysis & Prevention },
volume = {37},
number = {5},
pages = {910 - 921},
year = {2005},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2005.04.009},
url = {http://www.sciencedirect.com/science/article/pii/S0001457505000722},
author = {Ahmad Khorashadi and Debbie Niemeier and Venky Shankar and Fred Mannering},
keywords = {Injury severity},
keywords = {Truck accidents},
keywords = {Urban/rural differences},
keywords = {Multinomial logit },
abstract = {This study explores the differences between urban and rural driver injuries (both passenger-vehicle and large-truck driver injuries) in accidents that involve large trucks (in excess of 10,000 pounds). Using 4 years of California accident data, and considering four driver-injury severity categories (no injury, complaint of pain, visible injury, and severe/fatal injury), a multinomial logit analysis of the data was conducted. Significant differences with respect to various risk factors including driver, vehicle, environmental, road geometry and traffic characteristics were found to exist between urban and rural models. For example, in rural accidents involving tractor–trailer combinations, the probability of drivers’ injuries being severe/fatal increased about 26% relative to accidents involving single-unit trucks. In urban areas, this same probability increased nearly 700%. In accidents where alcohol or drug use was identified as being the primary cause of the accident, the probability of severe/fatal injury increased roughly 250% percent in rural areas and nearly 800% in urban areas. While many of the same variables were found to be significant in both rural and urban models (although often with quite different impact), there were 13 variables that significantly influenced driver-injury severity in rural but not urban areas, and 17 variables that significantly influenced driver-injury severity in urban but not rural areas. We speculate that the significant differences between rural and urban injury severities may be at least partially attributable to the different perceptual, cognitive and response demands placed on drivers in rural versus urban areas. }
}
@article{Carson200199,
title = {The effect of ice warning signs on ice-accident frequencies and severities },
journal = {Accident Analysis & Prevention },
volume = {33},
number = {1},
pages = {99 - 109},
year = {2001},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/S0001-4575(00)00020-8},
url = {http://www.sciencedirect.com/science/article/pii/S0001457500000208},
author = {Jodi Carson and Fred Mannering},
keywords = {Ice warning signs},
keywords = {Ice-accident frequencies},
keywords = {Roadway and roadside design },
abstract = {Signing of non-permanent road surface conditions, such as ice, is difficult because hazard formation, location, and duration are unpredictable. Subsequently, many state transportation departments have begun to question the sensibility of expending material and personnel resources to maintain ice warning signs when little proof exists of their effectiveness in improving highway safety. This research statistically studies the effectiveness of ice warning signs in reducing accident frequency and accident severity in Washington State. Our findings show that the presence of ice warning signs was not a significant factor in reducing ice-accident frequency or ice-accident severity. However, we were able to identify significant spatial, temporal, traffic, roadway and accident characteristics that influenced ice-accident frequency and severity. The identification of these characteristics will allow for better placement of ice warning signs and improvements in roadway and roadside design that can reduce the frequency and severity of ice-related accidents. }
}
@article{Washburn200373,
title = {Statistical modeling of vehicle emissions from inspection/maintenance testing data: an exploratory analysis––Reply },
journal = {Transportation Research Part D: Transport and Environment },
volume = {8},
number = {1},
pages = {73 - 74},
year = {2003},
note = {},
issn = {1361-9209},
doi = {http://dx.doi.org/10.1016/S1361-9209(02)00008-1},
url = {http://www.sciencedirect.com/science/article/pii/S1361920902000081},
author = {Scott Washburn and Fred Mannering}
}
@article{Ulfarsson2004135,
title = {Differences in male and female injury severities in sport-utility vehicle, minivan, pickup and passenger car accidents },
journal = {Accident Analysis & Prevention },
volume = {36},
number = {2},
pages = {135 - 147},
year = {2004},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/S0001-4575(02)00135-5},
url = {http://www.sciencedirect.com/science/article/pii/S0001457502001355},
author = {Gudmundur F. Ulfarsson and Fred L. Mannering},
keywords = {Gender differences},
keywords = {Injury severity},
keywords = {Sport-utility vehicles},
keywords = {Multinomial logit},
keywords = {Transferability},
keywords = {Elasticity },
abstract = {This research explores differences in injury severity between male and female drivers in single and two-vehicle accidents involving passenger cars, pickups, sport-utility vehicles (SUVs), and minivans. Separate multivariate multinomial logit models of injury severity are estimated for male and female drivers. The models predict the probability of four injury severity outcomes: no injury (property damage only), possible injury, evident injury, and fatal/disabling injury. The models are conditioned on driver gender and the number and type of vehicles involved in the accident. The conditional structure avoids bias caused by men and women’s different reporting rates, choices of vehicle type, and their different rates of participation as drivers, which would affect a joint model of all crashes. We found variables that have opposite effects for the genders, such as striking a barrier or a guardrail, and crashing while starting a vehicle. The results suggest there are important behavioral and physiological differences between male and female drivers that must be explored further and addressed in vehicle and roadway design. }
}
@article{Mannering2002154,
title = {An exploratory analysis of automobile leasing by \{US\} households },
journal = {Journal of Urban Economics },
volume = {52},
number = {1},
pages = {154 - 176},
year = {2002},
note = {},
issn = {0094-1190},
doi = {http://dx.doi.org/10.1016/S0094-1190(02)00009-8},
url = {http://www.sciencedirect.com/science/article/pii/S0094119002000098},
author = {Fred Mannering and Clifford Winston and William Starkey},
keywords = {Automobile leasing},
keywords = {Upgrade behavior},
keywords = {Nested-logit },
abstract = {The share of new automobiles leased in the United States increased from 3% in 1984 to 30% by 1998. This paper explores the motivations behind consumers' preference for leasing by developing a model of vehicle acquisition decisions, including the type of vehicle to drive and whether to lease or purchase it. We find that leasing's recent popularity is largely attributable to its role in facilitating vehicle upgrading by high-income households. Because such households represent a small share of \{US\} households, we question projections that leasing will capture ever greater shares of the new vehicle market. }
}
@article{Washburn200121,
title = {Statistical modeling of vehicle emissions from inspection/maintenance testing data: an exploratory analysis },
journal = {Transportation Research Part D: Transport and Environment },
volume = {6},
number = {1},
pages = {21 - 36},
year = {2001},
note = {},
issn = {1361-9209},
doi = {http://dx.doi.org/10.1016/S1361-9209(00)00011-0},
url = {http://www.sciencedirect.com/science/article/pii/S1361920900000110},
author = {Scott Washburn and Joseph Seet and Fred Mannering},
keywords = {Vehicle emissions},
keywords = {Inspection/maintenance testing },
abstract = {Many metropolitan areas in the United States use vehicle inspection and maintenance (I/M) programs as a means of identifying high-polluting vehicles. While the effectiveness of such programs is debatable, the cost is undeniable, with millions of dollars spent in testing and millions more lost in the time motorists expend to participate in such programs. At the core of these costs is the blanket approach of requiring all vehicles to be tested. This paper sets the groundwork for a procedure that can be used to selectively target those vehicles most likely to be pollution violators. Using I/M data collected in the Seattle area in 1994, carbon monoxide, carbon dioxide and hydrocarbon emissions were modeled simultaneously using three-stage least squares. Our results show that vehicle age, vehicle manufacturer, number of engine cylinders, odometer reading, and whether or not oxygenated fuels were in use all play a significant role in determining I/M emission test results and these statistical findings can be used to form the basis for the selective sampling of vehicles for I/M testing. }
}
@article{Chang1999579,
title = {Analysis of injury severity and vehicle occupancy in truck- and non-truck-involved accidents },
journal = {Accident Analysis & Prevention },
volume = {31},
number = {5},
pages = {579 - 592},
year = {1999},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/S0001-4575(99)00014-7},
url = {http://www.sciencedirect.com/science/article/pii/S0001457599000147},
author = {Li-Yen Chang and Fred Mannering},
keywords = {Trucks},
keywords = {Accident severity},
keywords = {Occupant injury},
keywords = {Risk factors},
keywords = {Logit modeling },
abstract = {The impact that large trucks have on accident severity has long been a concern in the accident analysis literature. One important measure of accident severity is the most severely injured occupant in the vehicle. Such data are routinely collected in state accident data files in the U.S. Among the many risk factors that determine the most severe level of injury sustained by vehicle occupants, the number of occupants in the vehicle is an important factor. These effects can be significant because vehicles with higher occupancies have an increased likelihood of having someone seriously injured. This paper studies the occupancy/injury severity relationship using Washington State accident data. The effects of large trucks, which are shown to have a significant impact on the most severely injured vehicle occupant, are accounted for by separately estimating nested logit models for truck-involved accidents and for non-truck-involved accidents. The estimation results uncover important relationships between various risk factors and occupant injury. In addition, by comparing the accident characteristics between truck-involved accidents and non-truck-involved accidents, the risk factors unique to large trucks are identified along with the relative importance of such factors. The findings of this study demonstrate that nested logit modeling, which is able to take into account vehicle occupancy effects and identify a broad range of factors that influence occupant injury, is a promising methodological approach. }
}
@article{Choocharukul2004677,
title = {User perceptions and engineering definitions of highway level of service: an exploratory statistical comparison },
journal = {Transportation Research Part A: Policy and Practice },
volume = {38},
number = {9–10},
pages = {677 - 689},
year = {2004},
note = {},
issn = {0965-8564},
doi = {http://dx.doi.org/10.1016/j.tra.2004.08.001},
url = {http://www.sciencedirect.com/science/article/pii/S0965856404000692},
author = {Kasem Choocharukul and Kumares C. Sinha and Fred L. Mannering},
abstract = {The level of service (LOS) concept in the Highway Capacity Manual has been used as a qualitative measure representing freeway operational conditions for over 35 years. One key element that has not been adequately addressed is how road users perceive LOS. This exploratory research examines road-user perceptions of freeway \{LOS\} by presenting study participants with a series of video clips of various traffic conditions (taken from cameras on overpasses to allow a complete view of the traffic stream) and asking them their perceptions of LOS. A random effects ordered probability model is then used to statistically link participant-recorded perceptions of \{LOS\} with measurable traffic conditions (speed, density, flow, percentage of trucks, vehicle headways) and participant characteristics. The findings suggest that the Highway Capacity Manual’s use of traffic density as a single performance measure for \{LOS\} does not accurately reflect road-user perceptions. The statistical analysis shows that a number of attributes besides traffic density determine public perceptions of \{LOS\} and that these perceptions vary depending on both traffic conditions and road-user characteristics. }
}
@article{Gkritza2006213,
title = {Airport security screening and changing passenger satisfaction: An exploratory assessment },
journal = {Journal of Air Transport Management },
volume = {12},
number = {5},
pages = {213 - 219},
year = {2006},
note = {},
issn = {0969-6997},
doi = {http://dx.doi.org/10.1016/j.jairtraman.2006.03.001},
url = {http://www.sciencedirect.com/science/article/pii/S0969699706000354},
author = {Konstantina Gkritza and Debbie Niemeier and Fred Mannering},
keywords = {Airport security},
keywords = {Airline passenger satisfaction },
abstract = {Since September 11, 2001, airport screening procedures in the \{US\} have been continuously evolving. For example, the passenger screening process is now trying to strike a balance between security and customer service (i.e. minimizing wait times). This balancing act has important implications not only for passenger safety, but also for the financial stability of an airline industry that is faced with volatile energy prices and sometimes burdensome labor agreements. Using data from 2002 and 2003, we estimate multinomial logit models to uncover factors that determine passenger satisfaction at security screening points. Our findings show that, while wait times at security screening points are significant determinants of passenger satisfaction, many other factors come into play. Moreover, the results show that the determinants of customer satisfaction are not stable over time. This suggests that further refinements in airport screening procedures should give careful consideration to the factors underlying passenger satisfaction, and how these might change over time, rather than focusing exclusively on minimizing wait times at passenger screening points. }
}
@article{Barfield1993105,
title = {Behavioral and human factors issues in advanced traveler information systems },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {1},
number = {2},
pages = {105 - 106},
year = {1993},
note = {},
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/0968-090X(93)90007-3},
url = {http://www.sciencedirect.com/science/article/pii/0968090X93900073},
author = {Woodrow Barfield and Fred Mannering}
}
@article{Mannering1995339,
title = {Travelers' preferences for in-vehicle information systems: An exploratory analysis },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {3},
number = {6},
pages = {339 - 351},
year = {1995},
note = {},
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/0968-090X(96)00014-9},
url = {http://www.sciencedirect.com/science/article/pii/0968090X96000149},
author = {Fred Mannering and Soon-Gwan Kim and Linda Ng and Woodrow Barfield},
abstract = {A sample of travelers' preferences toward in-vehicle traffic information systems was undertaken and appropriate statistical models were estimated. Specifically, ordered logit and regression analyses were conducted to quantify travelers' ratings of the importance of in-vehicle system attributes, and the distance ahead that they prefer to be notified of various types of information provided by in-vehicle systems. Model estimation results show that travelers' socio-economics, habitual travel patterns, commute congestion levels and attitudes toward in-vehicle technologies are significant determinants of travelers' importance ratings and the preferred distance ahead of in-vehicle system information. These model results provide important information for both marketing and design of in-vehicle information systems. }
}
@article{Jones1991239,
title = {Analysis of the frequency and duration of freeway accidents in Seattle },
journal = {Accident Analysis & Prevention },
volume = {23},
number = {4},
pages = {239 - 255},
year = {1991},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/0001-4575(91)90003-N},
url = {http://www.sciencedirect.com/science/article/pii/000145759190003N},
author = {Bryan Jones and Lester Janssen and Fred Mannering},
abstract = {Accidents occurring on congested urban freeways can have enormous impacts in terms of lost commuter time. This paper presents an appropriate statistical analysis of urban freeway accident frequency and duration and discusses how this analysis can be used to guide management strategies that seek to reduce the traffic-related impacts of accidents. The findings and demonstration of analysis procedures should be of considerable value to ongoing and future studies in this area. }
}
@article{Mannering1994132,
title = {Author's rebuttal },
journal = {Accident Analysis & Prevention },
volume = {26},
number = {1},
pages = {132 - 133},
year = {1994},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/0001-4575(94)90081-7},
url = {http://www.sciencedirect.com/science/article/pii/0001457594900817},
author = {Fred L. Mannering}
}
@article{Mannering199435,
title = {Statistical analysis of commuters' route, mode, and departure time flexibility },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {2},
number = {1},
pages = {35 - 47},
year = {1994},
note = {},
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/0968-090X(94)90018-3},
url = {http://www.sciencedirect.com/science/article/pii/0968090X94900183},
author = {Fred Mannering and Soon-Gwan Kim and Woodrow Barfield and Linda Ng},
abstract = {This paper studies the effects of traffic information on Seattle-area commuters. Models of commuters' route-change frequency, the duration of traffic delay needed to induce a route change, and the influence of pre-trip traffic information on departure-time choice, mode choice, and route choice are estimated. Two modeling techniques are used in these estimations: an ordered logit probability approach and a Weibull duration model with a heterogeneity correction term. The findings of these model estimations provide important insights into how traveler information systems should be designed, implemented, and marketed. }
}
@article{Mannering199099,
title = {Occurence, frequency, and duration of commuters' work-to-home departure delay },
journal = {Transportation Research Part B: Methodological },
volume = {24},
number = {2},
pages = {99 - 109},
year = {1990},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/0191-2615(90)90022-Q},
url = {http://www.sciencedirect.com/science/article/pii/019126159090022Q},
author = {Fred L. Mannering and Mohammad M. Hamed},
abstract = {This paper investigates commuters' decision to delay their departure from work to home, in an effort to avoid traffic congestion. A sample of commuters, from the congested Seattle metropolitan area, is used to estimate a model of the decision to delay homeward departure as well as models of the frequency and duration of this delay. The estimation results suggest, as expected, that traffic system characteristics dominate the delay choice, with socioeconomic characteristics and the characteristics of the area near the work location (which provides activity opportunities that can be undertaken during the departure delay) playing a lesser role. The estimated magnitude of influence that these determinants have, on the delay choice, has important implications for future departure-time-choice research. }
}
@article{Mannering198953,
title = {Poisson analysis of commuter flexibility in changing routes and departure times },
journal = {Transportation Research Part B: Methodological },
volume = {23},
number = {1},
pages = {53 - 60},
year = {1989},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/0191-2615(89)90023-4},
url = {http://www.sciencedirect.com/science/article/pii/0191261589900234},
author = {Fred L. Mannering},
abstract = {This paper investigates the determinants of commuter flexibility in changing routes and departure times for the morning trip to work. A sample of commuters in a congested metropolitan area is used to estimate Poisson regressions of how often commuters change routes and departure times per month. The estimation results provide valuable insight into the effects of traffic system and socioeconomic conditions on the frequency of route and departure time changes. The results also have significant implications for real-time traffic information systems and future research on the route and departure time choice decision-making process. }
}
@article{Mannering1985243,
title = {Consumer valuation of foreign and domestic vehicle attributes: Econometric analysis and implications for auto demand },
journal = {Transportation Research Part A: General },
volume = {19},
number = {3},
pages = {243 - 251},
year = {1985},
note = {},
issn = {0191-2607},
doi = {http://dx.doi.org/10.1016/0191-2607(85)90013-5},
url = {http://www.sciencedirect.com/science/article/pii/0191260785900135},
author = {Fred Mannering and Hani Mahmassani},
abstract = {Previous models of vehicle type choice have assumed that consumer valuation of vehicle attributes was consistent across foreign and domestic vehicles. In this paper, we present a model that allows for different attribute valuations between foreign and domestic vehicles. The model was estimated using national data on households who purchased new vehicles in the fall of 1979 and the spring of 1980. The estimation results indicate the presence of a substantial difference in consumer valuation of attributes between foreign and domestic vehicles. Moreover, the results indicate that studies that ignore this difference will produce erroneous marginal rates of substitution and vehicle type choice elasticities, and will ultimately lead to a misinterpretation of household vehicle demand. }
}
@article{Shankar1995371,
title = {Effect of roadway geometrics and environmental factors on rural freeway accident frequencies },
journal = {Accident Analysis & Prevention },
volume = {27},
number = {3},
pages = {371 - 389},
year = {1995},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/0001-4575(94)00078-Z},
url = {http://www.sciencedirect.com/science/article/pii/000145759400078Z},
author = {Venkataraman Shankar and Fred Mannering and Woodrow Barfield},
keywords = {Negative binomial},
keywords = {Accident frequency },
abstract = {This paper explores the frequency of occurrence of highway accidents on the basis of a multivariate analysis of roadway geometrics (e.g. horizontal and vertical alignments), weather, and other seasonal effects. Based on accident data collected in the field, a negative binomial model of overall accident frequencies is estimated along with models of the frequency of specific accident types. Interactions between weather and geometric variables are proposed as part of the model specifications. The results of the analysis uncover important determinants of accident frequency. By studying the relationship between weather and geometric elements, this paper offers insight into potential measures to counter the adverse effects of weather on highway sections with challenging geometrics. }
}
@article{Mannering1990371,
title = {Commuter welfare approach to high occupancy vehicle lane evaluation: An exploratory analysis },
journal = {Transportation Research Part A: General },
volume = {24},
number = {5},
pages = {371 - 379},
year = {1990},
note = {},
issn = {0191-2607},
doi = {http://dx.doi.org/10.1016/0191-2607(90)90049-C},
url = {http://www.sciencedirect.com/science/article/pii/019126079090049C},
author = {Fred L. Mannering and Mohammad M. Hamed},
abstract = {Exclusive high occupancy vehicle lanes, which have become a popular method of addressing the problem of urban traffic congestion, are often justified on the basis of inappropriate measures of effectiveness, and limited analyses. This paper demonstrates a theoretically consistent and defensible approach of high occupancy vehicle lane evaluation based on consumer welfare theory. The potential suitability of this welfare approach is illustrated in the context of a dynamic traffic equilibrium model. }
}
@article{Ng1995113,
title = {A survey-based methodology to determine information requirements for advanced traveler information systems },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {3},
number = {2},
pages = {113 - 127},
year = {1995},
note = {},
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/0968-090X(95)00001-Y},
url = {http://www.sciencedirect.com/science/article/pii/0968090X9500001Y},
author = {Linda Ng and Woodrow Barfield and Fred Mannering},
abstract = {This paper discusses three nationwide surveys designed to obtain user information requirements for an advanced traveler information system (ATIS) and the \{ATIS\} portion of commercial vehicle operations (CVO). A description of the survey methodology for targeting the three populations—private vehicle drivers, commercial vehicle drivers, and commercial vehicle operators—is provided, as well as the implications for the design of \{ATIS\} based on driving behavior and preference. Analysis of the data from the 1,610 returned surveys revealed that commercial drivers and private drivers valued road and traffic information as the most important \{ATIS\} service, whereas commercial vehicle operators (or dispatchers) valued the ability to have two-way communication as most important. This study also revealed that dispatchers were willing to pay significantly more for an \{ATIS\} than drivers. Finally, the data indicated that, of the four main nationwide geographical areas considered in the survey, no differences in response to the survey questions were observed. Implications of the results for the design of \{ATIS\} are discussed. }
}
@article{Shankar1996391,
title = {Statistical analysis of accident severity on rural freeways },
journal = {Accident Analysis & Prevention },
volume = {28},
number = {3},
pages = {391 - 401},
year = {1996},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/0001-4575(96)00009-7},
url = {http://www.sciencedirect.com/science/article/pii/0001457596000097},
author = {Venkataraman Shankar and Fred Mannering and Woodrow Barfield},
keywords = {Nested logic},
keywords = {Accident injuries},
keywords = {Highway safety },
abstract = {The growing concern about the possible safety-related impacts of Intelligent Transportation Systems (ITS) has focused attention on the need to develop new statistical approaches to predict accident severity. This paper presents a nested logit formulation as a means for determining accident severity given that an accident has occurred. Four levels of severity are considered: 1. (1) property damage only, 2. (2) possible injury, 3. (3) evident injury, and 4. (4) disabling injury or fatality. Using 5-year accident data from a 61 km section of rural interstate in Washington State (which has been selected as an \{ITS\} demonstration site), we estimate a nested logit model of accident severity. The estimation results provide valuable evidence on the effect that environmental conditions, highway design, accident type, driver characteristics and vehicle attributes have on accident severity. Our findings show that the nested logit formulation is a promising approach to evaluate the impact that \{ITS\} or other safety-related countermeasures may have on accident severities. }
}
@article{Mannering19861,
title = {A note on endogenous variables in household vehicle utilization equations },
journal = {Transportation Research Part B: Methodological },
volume = {20},
number = {1},
pages = {1 - 6},
year = {1986},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/0191-2615(86)90031-7},
url = {http://www.sciencedirect.com/science/article/pii/0191261586900317},
author = {Fred L. Mannering},
abstract = {This paper presents an empirical analysis of the statistical bias resulting from the endogeniety of vehicle specific attributes in econometric models of household vehicle utilization. Using data from a recent U.S. household survey, both corrected and uncorrected vehicle utilization models are estimated. A comparison of these estimation results reflects the substantial bias in model coefficients, price elasticities and income elasticities that can result if the endogeneity of vehicle specific attributes is not considered. }
}
@article{Ng1995353,
title = {Statistical analysis of commercial driver and dispatcher requirements for advanced traveler information systems },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {3},
number = {6},
pages = {353 - 369},
year = {1995},
note = {},
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/0968-090X(96)00015-0},
url = {http://www.sciencedirect.com/science/article/pii/0968090X96000150},
author = {Linda Ng and Ralph L. Wessels and Duke Do and Fred Mannering and Woodrow Barfield},
abstract = {This paper analyzes the responses from two nationwide surveys designed to obtain user information requirements for the design of advanced traveler information systems (ATIS) and commercial vehicle operations (CVO) with respect to commercial system operators (dispatchers) and commercial vehicle drivers. A total of 673 returned surveys (348 dispatcher surveys and 325 commercial driver surveys), were used in the analysis. Mathematical models were developed, using a binomial logit to predict whether the commercial driver or dispatcher would use an intelligent transportation system, and an ordered probit to estimate the importance of information (i.e. route and navigation, roadside services, personal communication and road and traffic information) to be provided by in-vehicle information systems. The results of this study provide guidelines for the design of information systems and help define informational requirements for users of ATIS/CVO. }
}
@article{Shankar1996183,
title = {An exploratory multinomial logit analysis of single-vehicle motorcycle accident severity },
journal = {Journal of Safety Research },
volume = {27},
number = {3},
pages = {183 - 194},
year = {1996},
note = {},
issn = {0022-4375},
doi = {http://dx.doi.org/10.1016/0022-4375(96)00010-2},
url = {http://www.sciencedirect.com/science/article/pii/0022437596000102},
author = {Venkataraman Shankar and Fred Mannering},
abstract = {Most previous research on motorcycle accident severity has focused on univariate relationships between severity and an explanatory variable of interest (e.g., helmet use). The potential ambiguity and bias that univariate analyses create in identifying the causality of severity has generated the need for multivariate analyses in which the effects of all factors that influence accident severity are considered. This paper attempts to address this need by presenting a multinomial logit formulation of motorcyclerider accident severity in single-vehicle collisions. Five levels of severity are considered: 1. (a) property damage only, 2. (b) possible injury, 3. (c) evident injury, 4. (d) disabling injury, and 5. (e) fatality. Using 5-year statewide data on single-vehicle motorcycle accidents from the state of Washington, we estimate a multivariate model of motorcycle-rider severity that considers environmental factors, roadway conditions, vehicle characteristics, and rider attributes. Our findings show that the multinomial logit formulation that we use is a promising approach to evaluate the determinants of motorcycle accident severity. }
}
@article{Mannering1983183,
title = {An econometric analysis of vehicle use in multivehicle households },
journal = {Transportation Research Part A: General },
volume = {17},
number = {3},
pages = {183 - 189},
year = {1983},
note = {},
issn = {0191-2607},
doi = {http://dx.doi.org/10.1016/0191-2607(83)90040-7},
url = {http://www.sciencedirect.com/science/article/pii/0191260783900407},
author = {Fred L. Mannering},
abstract = {The significance of the multivehicle household in the U.S. has increased substantially in recent years to the point where over 80% of household vehicles holdings are owned by multivehicle households. Despite this fact. traditional travel demand models have not explored the determinants of individual vehicle use in such households, even though knowledge of vehicle usage allocations within household fleets is critical to subsequent fuel consumption forecasts. This paper presents a discussion of vehicle use in multivehicle households and then develops an appropriate modeling specification. The specification consists of a simultaneous equation system which is estimated using a sample of two-vehicle households from a recently conducted national survey. The estimation results proved to be quite satisfactory and the model was applied to forecast policy impacts. The results underscore the importance of income and vehicle fuel efficiency in the allocation of use to household vehicles, and suggests that the ability of multivehicle households to substitute the use of more fuel efficient vehicles for less efficient ones (thereby maintaining higher usage levels) can have potentially significant consequences for traditional vehicle miles traveled (VMT)—price elasticity estimates. }
}
@article{Mannering1985265,
title = {Recent directions in automobile demand modeling },
journal = {Transportation Research Part B: Methodological },
volume = {19},
number = {4},
pages = {265 - 274},
year = {1985},
note = {Special Issue Economic Models of Automobile Demand },
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/0191-2615(85)90035-9},
url = {http://www.sciencedirect.com/science/article/pii/0191261585900359},
author = {Fred L. Mannering and Kenneth Train},
abstract = {We identify seven areas in which recent research on auto demand has made significant progress. We discuss the importance of these areas in understanding and predicting auto demand and describe the methods that researchers have used to address them. Finally, we identify the issues that this research indicates require further investigation. }
}
@article{Shankar1998311,
title = {Modeling the endogeneity of lane-mean speeds and lane-speed deviations: a structural equations approach },
journal = {Transportation Research Part A: Policy and Practice },
volume = {32},
number = {5},
pages = {311 - 322},
year = {1998},
note = {},
issn = {0965-8564},
doi = {http://dx.doi.org/10.1016/S0965-8564(98)00003-2},
url = {http://www.sciencedirect.com/science/article/pii/S0965856498000032},
author = {Venkataraman Shankar and Fred Mannering},
keywords = {structural equations},
keywords = {three-stage least squares},
keywords = {speed deviation },
abstract = {This paper attempts to macroscopically address endogeneity issues related to lane-mean traffic speeds and lane-speed deviations. Methodologically, we seek to provide a better understanding of mean speeds and speed deviations across the lanes of a multilane highway. In so doing, the work may eventually be applied to better understand highway safety and the effects that lane-mean and lane speed deviations have on highway safety. We propose a structural model that relates mean speed and speed deviations by lane and is contemporaneously influenced by environmental, temporal, and traffic flow factors. Spot speed and vehicle classification data measured by lane in both the eastbound and westbound directions of Interstate 90 (I-90) in Washington State are used to develop the empirical relationships. The findings show that lane-mean speeds are endogenously related with adjacent lane speeds and exogenously related with associated environmental, traffic flow and temporal factors, while lane-speed deviations are endogenously related not only with adjacent lane speed deviations but also, through forward causality, lane-mean speeds and exogenously related with environmental, traffic flow and temporal factors as well. The approach shows significant promise in unraveling cause–effect relationships affecting macroscopic traffic flow continuums. }
}
@article{Mannering1987487,
title = {Decisions relating to alcohol-impaired driving: An exploratory analysis },
journal = {Accident Analysis & Prevention },
volume = {19},
number = {6},
pages = {487 - 495},
year = {1987},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/0001-4575(87)90049-2},
url = {http://www.sciencedirect.com/science/article/pii/0001457587900492},
author = {Fred L. Mannering and William K. Bottiger and Kent L. Black},
abstract = {This paper focuses on an individual's decision to drive or not to drive after drinking. To evaluate this decision, a utility maximizing probabilistic choice model is specified and estimated using a sample of college students. The estimation results provide interesting insights relating to the potential effectiveness of drinking-driving countermeasures, and suggest that the most effective methods of reducing the probability of driving after drinking are those advertising and awareness campaigns that focus on altering individual preferences. }
}
@article{Mannering199521,
title = {Statistical analysis of motorcyclists' perceived accident risk },
journal = {Accident Analysis & Prevention },
volume = {27},
number = {1},
pages = {21 - 31},
year = {1995},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/0001-4575(94)00041-J},
url = {http://www.sciencedirect.com/science/article/pii/000145759400041J},
author = {Fred L. Mannering and Lawrence L. Grodsky},
abstract = {Motorcycling is generally recognized as a relatively risky activity, but surprisingly little is known about motorcyclists' perception of this risk. This paper presents a survey of motorcyclists' perceived likelihood of being involved in an accident and a statistical analysis of the factors determining this likelihood. Our results show that motorcyclists have a reasonable grasp of the factors that increase the likelihood of accident involvement. These factors include exposure (miles ridden), regularly riding above the speed limit, and passing vehicles on the shoulder or passing between lanes of traffic. The findings suggest that motorcycle accidents are, for the most part, not the result of misjudgments about the overall risk of motorcycling. }
}
@article{Mannering199377,
title = {Male/female driver characteristics and accident risk: Some new evidence },
journal = {Accident Analysis & Prevention },
volume = {25},
number = {1},
pages = {77 - 84},
year = {1993},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/0001-4575(93)90098-H},
url = {http://www.sciencedirect.com/science/article/pii/000145759390098H},
author = {Fred L. Mannering},
abstract = {Due to the high correlation that generally exists among driver characteristics, as well as the overall complexity of the factors involved, the role that gender plays in the relationship between driver characteristics and accident risk has been difficult to quantify using traditional statistical approaches. This paper attempts to provide some new insight by using hazard functions and a sample of University of Washington drivers. The subsequent empirical analysis uncovers important differences in the relationship between male and female driver characteristics and their respective accident risk. }
}
@comment{{Ezra Hauer PAPERS}}
@comment{{Rune Elvik PAPERS}}
@article{Elvik201315,
title = {Effects on accidents of changes in the use of studded tyres in major cities in Norway: A long-term investigation },
journal = {Accident Analysis & Prevention },
volume = {54},
number = {0},
pages = {15 - 25},
year = {2013},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2013.02.004},
url = {http://www.sciencedirect.com/science/article/pii/S000145751300033X},
author = {Rune Elvik and Lasse Fridstrøm and Joanna Kaminska and Sunniva Frislid Meyer},
keywords = {Studded tyres},
keywords = {Evaluation study},
keywords = {Cities},
keywords = {Negative binomial regression},
keywords = {Accident modification function },
abstract = {This paper reports the findings of two studies made eleven years apart in Norway (Fridstrøm, 2000; Elvik and Kaminska, 2011) to evaluate effects on accidents of changes in the use of studded tyres in major cities in Norway. The first study covered the period from 1991 to 2000, the second study covered the period from 2002 to 2009. In both these periods, large changes in the percentage of cars using studded tyres were found in the cities that were included in the study. There was, in most cities, a tendency for the use of studded tyres to go down. Effects of these changes on injury accidents were evaluated by means of negative binomial regression models, using city and day as the unit of analysis, and including more than twenty explanatory variables in order to control for confounding factors. The effects of changes in the percentage of cars using studded tyres were well described by an accident modification function (dose–response curve), relating the size of changes in the number of accident to the size of the change in the use of studded tyres. Accidents during the season when the use of studded tyres is permitted were found to increase by about 5 percent if the use of studded tyres was reduced by 25 percentage points (e.g. from 50 to 25 percent) and to decline by about 2 percent when the use of studded tyres increased by 20 percentage points. }
}
@article{Flügel20151,
title = {Car drivers’ valuation of landslide risk reductions },
journal = {Safety Science },
volume = {77},
number = {0},
pages = {1 - 9},
year = {2015},
note = {},
issn = {0925-7535},
doi = {http://dx.doi.org/10.1016/j.ssci.2015.03.006},
url = {http://www.sciencedirect.com/science/article/pii/S0925753515000648},
author = {Stefan Flügel and Luis I. Rizzi and Knut Veisten and Rune Elvik and Juan de Dios Ortúzar},
keywords = {Fatality},
keywords = {Injury},
keywords = {Internet survey},
keywords = {Stated choice},
keywords = {Mixed logit },
abstract = {Abstract Approximately one car occupant per year is killed as a result of landslides or avalanches in Norway, compared to 150–200 fatalities due to accidents. Still, protection from landslides is a major transport safety issue, possibly due to the concern and dread felt by the car-driving population travelling through landslide-prone areas. A main challenge when valuing landslide risk economically lies in distinguishing it from the standard road accident risk of having a collision or running off the road. In this paper we present an approach to the valuation of landslide risk, using a stated choice experiment where internet survey respondents were asked to choose between route alternatives that differed in terms of landslide risk, casualty risk, time use and cost. Thus, landslide risk was explicitly valued as an attribute, besides travel time and casualty risk, conveying a valuation of a feature different than the risk of fatality or injury caused by ordinary road accidents. The stated route choice data were analysed using mixed logit models. We obtained point estimates for the value of landslide risk removal per kilometre driven ranging from about \{EUR\} 0.2 to \{EUR\} 0.3. These results indicate that landslide risk was perceived as something different from casualty risk related to collisions with other road users or driving off the road. More research is warranted for developing the procedures for valuation of landslide risk before such valuations can enter as input into cost-benefit analyses of landslide-reducing measures. }
}
@article{Elvik201526,
title = {Methodological guidelines for developing accident modification functions },
journal = {Accident Analysis & Prevention },
volume = {80},
number = {0},
pages = {26 - 36},
year = {2015},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2015.03.038},
url = {http://www.sciencedirect.com/science/article/pii/S0001457515001232},
author = {Rune Elvik},
keywords = {Accident modification function},
keywords = {Methods},
keywords = {Guidelines},
keywords = {Road safety},
keywords = {Evaluation studies },
abstract = {Abstract This paper proposes methodological guidelines for developing accident modification functions. An accident modification function is a mathematical function describing systematic variation in the effects of road safety measures. The paper describes ten guidelines. An example is given of how to use the guidelines. The importance of exploratory analysis and an iterative approach in developing accident modification functions is stressed. The example shows that strict compliance with all the guidelines may be difficult, but represents a level of stringency that should be strived for. Currently the main limitations in developing accident modification functions are the small number of good evaluation studies and the often huge variation in estimates of effect. It is therefore still not possible to develop accident modification functions for very many road safety measures. }
}
@article{Elvik201515,
title = {Some implications of an event-based definition of exposure to the risk of road accident },
journal = {Accident Analysis & Prevention },
volume = {76},
number = {0},
pages = {15 - 24},
year = {2015},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2014.12.011},
url = {http://www.sciencedirect.com/science/article/pii/S000145751400390X},
author = {Rune Elvik},
keywords = {Exposure},
keywords = {Event},
keywords = {Learning},
keywords = {Risk},
keywords = {Probability },
abstract = {Abstract This paper proposes a new definition of exposure to the risk of road accident as any event, limited in space and time, representing a potential for an accident to occur by bringing road users close to each other in time or space of by requiring a road user to take action to avoid leaving the roadway. A typology of events representing a potential for an accident is proposed. Each event can be interpreted as a trial as defined in probability theory. Risk is the proportion of events that result in an accident. Defining exposure as events demanding the attention of road users implies that road users will learn from repeated exposure to these events, which in turn implies that there will normally be a negative relationship between exposure and risk. Four hypotheses regarding the relationship between exposure and risk are proposed. Preliminary tests support these hypotheses. Advantages and disadvantages of defining exposure as specific events are discussed. It is argued that developments in vehicle technology are likely to make events both observable and countable, thus ensuring that exposure is an operational concept. }
}
@article{Elvik201427,
title = {Problems in determining the optimal use of road safety measures },
journal = {Research in Transportation Economics },
volume = {47},
number = {0},
pages = {27 - 36},
year = {2014},
note = {Appraisal in Transport },
issn = {0739-8859},
doi = {http://dx.doi.org/10.1016/j.retrec.2014.09.016},
url = {http://www.sciencedirect.com/science/article/pii/S0739885914000572},
author = {Rune Elvik},
keywords = {Road safety measures},
keywords = {Optimal use},
keywords = {Economic analysis},
keywords = {Cost-effectiveness },
abstract = {Abstract This paper discusses some problems in determining the optimal use of road safety measures. The first of these problems is how best to define the baseline option, i.e. what will happen if no new safety measures are introduced. The second problem concerns choice of a method for selection of targets for intervention that ensures maximum safety benefits. The third problem is how to develop policy options to minimise the risk of indivisibilities and irreversible choices. The fourth problem is how to account for interaction effects between road safety measures when determining their optimal use. The fifth problem is how to obtain the best mix of short-term and long-term measures in a safety programme. The sixth problem is how fixed parameters for analysis, including the monetary valuation of road safety, influence the results of analyses. It is concluded that it is at present not possible to determine the optimal use of road safety measures precisely. One may at best determine a range that is likely to contain the optimal use of a set of measures. }
}
@article{Brüde201560,
title = {The turning point in the number of traffic fatalities: Two hypotheses about changes in underlying trends },
journal = {Accident Analysis & Prevention },
volume = {74},
number = {0},
pages = {60 - 68},
year = {2015},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2014.10.004},
url = {http://www.sciencedirect.com/science/article/pii/S0001457514003017},
author = {Ulf Brüde and Rune Elvik},
keywords = {Traffic fatalities},
keywords = {Long-term trends},
keywords = {Turning point},
keywords = {Traffic growth},
keywords = {Fatality rate },
abstract = {Abstract The number of traffic fatalities reached a peak in many highly motorised countries around 1970. Some previous studies have suggested that the turning point in the number of traffic fatalities was inevitable and did not reflect a change in the underlying trends influencing the number of traffic fatalities. Other studies suggest that trends in traffic growth and fatality rate changed from before to after the turning point. This paper proposes two hypotheses about the turning point in the number of traffic fatalities. One hypothesis is that the long-term trends in traffic growth and fatality rate were the same before and after the turning point. The other hypothesis is that the long-term trends in traffic growth and fatality rate were different before and after the turning point was reached, in particular that the annual percentage decline in fatality rate became greater after the turning point than before. Such a change would suggest that road safety policy became more effective. Analysis of data for six countries (Denmark, Great Britain, Netherlands, Norway, Sweden, United States) lends stronger support to the latter hypothesis than to the former. The lesson for policy makers, in particular in countries where the number of traffic fatalities is still growing, is that they should not expect a turning point to be reached without policy interventions. }
}
@article{Elvik201489,
title = {A comparative analysis of the effects of economic policy instruments in promoting environmentally sustainable transport },
journal = {Transport Policy },
volume = {33},
number = {0},
pages = {89 - 95},
year = {2014},
note = {},
issn = {0967-070X},
doi = {http://dx.doi.org/10.1016/j.tranpol.2014.02.025},
url = {http://www.sciencedirect.com/science/article/pii/S0967070X14000675},
author = {Rune Elvik and Farideh Ramjerdi},
keywords = {Economic policy instrument},
keywords = {Environmentally sustainable transport},
keywords = {Elasticity},
keywords = {Review},
keywords = {Meta-analysis },
abstract = {Abstract This paper presents a comparative analysis of the effects of economic policy instruments in promoting environmentally sustainable transport. Promoting environmentally sustainable transport is defined as follows: (1) Reducing the volume of motorised travel; (2) Transferring travel to modes generating less external effects, and (3) Modifying road user behaviour in a way that will reduce external effects of transport. External effects include accidents, congestion, traffic noise and emissions to air. Four economic policy instruments are compared: (1) Prices of motor fuel; (2) Congestion charges; (3) Toll schemes; (4) Reward systems giving incentives to reduce driving or change driver behaviour. The effects of these policy instruments are stated in terms of elasticities. All four economic policy instruments have negative elasticities, which means that they do promote environmentally sustainable transport. Long-term elasticities tend to be larger than short term elasticities. The long-term elasticities of reward systems are unknown. }
}
@article{Elvik2013624,
title = {Corrigendum to “The range of replications technique for assessing the external validity of road safety evaluation studies” [Accid. Anal. Prev. 45 (2012) 272–280] },
journal = {Accident Analysis & Prevention },
volume = {59},
number = {0},
pages = {624 - },
year = {2013},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2013.07.009},
url = {http://www.sciencedirect.com/science/article/pii/S0001457513002777},
author = {Rune Elvik}
}
@article{Elvik201310,
title = {A before–after study of the effects on safety of environmental speed limits in the city of Oslo, Norway },
journal = {Safety Science },
volume = {55},
number = {0},
pages = {10 - 16},
year = {2013},
note = {},
issn = {0925-7535},
doi = {http://dx.doi.org/10.1016/j.ssci.2012.12.007},
url = {http://www.sciencedirect.com/science/article/pii/S0925753512002895},
author = {Rune Elvik},
keywords = {Speed limit},
keywords = {Before–after study},
keywords = {Empirical Bayes method},
keywords = {City of Oslo },
abstract = {Starting in the winter of 2004–2005, a temporary speed limit of 60 km/h (ordinary speed limit: 80 km/h) was introduced on one of the major arterial roads in the city of Oslo, Norway as a measure to reduce air pollution, in particular the spread of micro-particles torn from the road surface by studded tyres. The speed limit, referred to as an environmental speed limit, was in force from November 1 to March 31. Similar speed limits were later introduced on other arterial roads in Oslo. This paper presents a before-and-after study of the effects of these speed limits on accidents. Four study designs were employed: (1) A simple before–after study; (2) A before–after study using the rest of Oslo as comparison group; (3) A before–after study based on accident rates; (4) An empirical Bayes before–after study. The latter design is widely regarded as the best, but its implementation in the current study was not straightforward. The number of injury accidents was reduced by about 25–35% according to all study designs. The estimate of effect did not differ much between the different study designs. It is reasonable to rule out confounding by chance variation, long-term trends, changes in traffic volume and regression-to-the-mean. It cannot be claimed, however, that the entire accident reduction was attributable to the environmental speed limits exclusively. }
}
@article{Elvik201364,
title = {Factors influencing safety in a sample of marked pedestrian crossings selected for safety inspections in the city of Oslo },
journal = {Accident Analysis & Prevention },
volume = {59},
number = {0},
pages = {64 - 70},
year = {2013},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2013.05.011},
url = {http://www.sciencedirect.com/science/article/pii/S0001457513002029},
author = {Rune Elvik and Michael W.J. Sørensen and Tor-Olav Nævestad},
keywords = {Marked pedestrian crossing},
keywords = {Safety-in-numbers},
keywords = {Negative binomial regression },
abstract = {Abstract This paper reports an analysis of factors influencing safety in a sample of marked pedestrian crossings in the city of Oslo, Norway. The sample consists of 159 marked pedestrian crossings where a total of 316 accidents were recorded during a period of five years. The crossings were selected for inspection because of they were, for various reasons, regarded as sub-standard. The sample of crossings is therefore not representative of all pedestrian crossings in Oslo. Factors influencing the number of accidents were studied by means of negative binomial regression. Factors that were studied included the volume of pedestrians and vehicles, the number of traffic lanes at the crossing, the location of the crossing (midblock or junction), the type of traffic control, the share of pedestrians using the crossing and the speed of approaching vehicles. The analysis confirmed the presence of a “safety-in-numbers” effect, meaning that an increase in the number of pedestrians is associated with a lower risk of accident for each pedestrian. Crossings located in four-leg junctions or roundabouts had more accidents than crossings located in three-leg junctions or on sections between junctions. A high share of pedestrians crossing the road outside the marked crossing was associated with a high number of accidents. Increased speed was associated with an increased number of accidents. }
}
@article{Elvik2014388,
title = {A review of game-theoretic models of road user behaviour },
journal = {Accident Analysis & Prevention },
volume = {62},
number = {0},
pages = {388 - 396},
year = {2014},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2013.06.016},
url = {http://www.sciencedirect.com/science/article/pii/S0001457513002443},
author = {Rune Elvik},
keywords = {Game-theory},
keywords = {Road user behaviour},
keywords = {Interaction},
keywords = {Review },
abstract = {Abstract This paper reviews game-theoretic models that have been developed to explain road user behaviour in situations where road users interact with each other. The paper includes the following game-theoretic models:1. A general model of the interaction between road users and their possible reaction to measures improving safety (behavioural adaptation). 2. Choice of vehicle size as a Prisoners’ dilemma game. 3. Speed choice as a co-ordination game. 4. Speed compliance as a game between drivers and the police. 5. Merging into traffic from an acceleration lane as a mixed-strategy game. 6. Choice of level of attention in following situations as an evolutionary game. 7. Choice of departure time to avoid congestion as variant of a Prisoners’ dilemma game. 8. Interaction between cyclists crossing the road and car drivers. 9. Dipping headlights at night well ahead of the point when glare becomes noticeable. 10. Choice of evasive action in a situation when cars are on collision course. The models reviewed are different in many respects, but a common feature of the models is that they can explain how informal norms of behaviour can develop among road users and be sustained even if these informal norms violate the formal regulations of the traffic code. Game-theoretic models are not applicable to every conceivable interaction between road users or to situations in which road users choose behaviour without interacting with other road users. Nevertheless, it is likely that game-theoretic models can be applied more widely than they have been until now. }
}
@article{Elvik201362,
title = {Paradoxes of rationality in road safety policy },
journal = {Research in Transportation Economics },
volume = {43},
number = {1},
pages = {62 - 70},
year = {2013},
note = {The Economics of Transportation Safety },
issn = {0739-8859},
doi = {http://dx.doi.org/10.1016/j.retrec.2012.12.008},
url = {http://www.sciencedirect.com/science/article/pii/S0739885912002120},
author = {Rune Elvik},
keywords = {Cost–benefit analysis},
keywords = {Road safety policy},
keywords = {Rationality},
keywords = {Paradox},
keywords = {Valuation },
abstract = {Rationality is an ideal for transport safety policy. As developed within normative welfare economics, rationality denotes the efficient use of safety measures based on cost–benefit analyses that include all relevant impacts of the measures. Efficiency in the technical sense of the term provides a perfectly clear and precise guideline for policy priorities. Nevertheless, some choices that are guided by cost–benefit analysis may strike us as paradoxical or counterintuitive. A paradox of rationality refers to any situation in which conflicting choices can both be defended as rational. This paper discusses a number of choices that may seem paradoxical. The first involves the choice between options that have identical impacts on safety, but in which these impacts are valued differently. The second deals with the tendency for preference reversals to occur when preferences for the provision of safety are aggregated. The third discusses the inability of conventional measures of willingness-to-pay to reflect the intensity of preferences. The fourth concerns the tendency for policy choice to favour the rich at the expense of the poor when willingness-to-pay is not adjusted for the marginal utility of money. A fifth situation refers to the fact that a policy option that looks attractive ex ante may fail an ex post compensation test because utility functions depend on health state. There is a potential conflict between individual and collective rationality with respect to the costs and benefits of some road safety measures. When developing a road safety programme, a set of road safety measures whose benefits exceed the costs when considered as stand-alone measures could have benefits smaller than cost when combined in a programme consisting of all the measures. Finally, there is a potential conflict between efficiency and negotiated consensus as mechanisms of resource allocation in the public sector. The sources of the paradoxes and ways of avoiding them are discussed. Some of the paradoxes can be avoided if changes in risk are valued in terms of a fixed price per unit of risk rather than according to a non-linear demand function. }
}
@article{Elvik2013254,
title = {Risk of road accident associated with the use of drugs: A systematic review and meta-analysis of evidence from epidemiological studies },
journal = {Accident Analysis & Prevention },
volume = {60},
number = {0},
pages = {254 - 267},
year = {2013},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2012.06.017},
url = {http://www.sciencedirect.com/science/article/pii/S0001457512002412},
author = {Rune Elvik},
keywords = {Drugs},
keywords = {Accident risk},
keywords = {Epidemiological studies},
keywords = {Systematic review},
keywords = {Meta-analysis },
abstract = {Abstract This paper is a corrigendum to a previously published paper where errors were detected. The errors have been corrected in this paper. The paper is otherwise identical to the previously published paper. A systematic review and meta-analysis of studies that have assessed the risk of accident associated with the use of drugs when driving is presented. The meta-analysis included 66 studies containing a total of 264 estimates of the effects on accident risk of using illicit or prescribed drugs when driving. Summary estimates of the odds ratio of accident involvement are presented for amphetamines, analgesics, anti-asthmatics, anti-depressives, anti-histamines, benzodiazepines, cannabis, cocaine, opiates, penicillin and zopiclone (a sleeping pill). For most of the drugs, small or moderate increases in accident risk associated with the use of the drugs were found. Information about whether the drugs were actually used while driving and about the doses used was often imprecise. Most studies that have evaluated the presence of a dose-response relationship between the dose of drugs taken and the effects on accident risk confirm the existence of a dose-response relationship. Use of drugs while driving tends to have a larger effect on the risk of fatal and serious injury accidents than on the risk of less serious accidents (usually property-damage-only accidents). The quality of the studies that have assessed risk varied greatly. There was a tendency for the estimated effects of drug use on accident risk to be smaller in well-controlled studies than in poorly controlled studies. Evidence of publication bias was found for some drugs. The associations found cannot be interpreted as causal relationships, principally because most studies do not control very well for potentially confounding factors. }
}
@article{Elvik201357,
title = {Can a safety-in-numbers effect and a hazard-in-numbers effect co-exist in the same data? },
journal = {Accident Analysis & Prevention },
volume = {60},
number = {0},
pages = {57 - 63},
year = {2013},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2013.08.010},
url = {http://www.sciencedirect.com/science/article/pii/S0001457513003229},
author = {Rune Elvik},
keywords = {Safety-in-numbers},
keywords = {Hazard-in-numbers},
keywords = {Statistical artefact},
keywords = {Co-existence of effects },
abstract = {Abstract Safety-in-numbers denotes a non-linear relationship between exposure (traffic volume) and the number of accidents, characterised by declining risk as traffic volume increases. There is safety-in-numbers when the number of accidents increases less than proportional to traffic volume, e.g. a doubling of traffic volume is associated with less than a doubling of the number of accidents. Hazard-in-numbers, a less-used concept, refers to the opposite effect: the number of accidents increases more than in proportion to traffic volume, e.g. is more than doubled when traffic volume is doubled. This paper discusses whether a safety-in-numbers effect and a hazard-in-numbers effect can co-exist in the same data. It is concluded that both effects can exist in a given data set. The paper proposes to make a distinction between partial safety-in-numbers and complete safety-in-numbers. Another issue that has been raised in discussions about the safety-in-numbers effect is whether the effect found in some studies is an artefact created by the way exposure was measured. The paper discusses whether measuring exposure as a rate or a share, e.g. kilometres travelled per inhabitant per year, will generate a safety-in-numbers effect as a statistical artefact. It is concluded that this is the case. The preferred measure of exposure is a count of the number of road users. The count should not be converted to a rate or to the share any group of road user contribute to total traffic volume. }
}
@article{Elvik2013394,
title = {Can a road safety measure be both effective and ineffective at the same time? A game-theoretic model of the effects of daytime running lights },
journal = {Accident Analysis & Prevention },
volume = {59},
number = {0},
pages = {394 - 398},
year = {2013},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2013.06.039},
url = {http://www.sciencedirect.com/science/article/pii/S0001457513002674},
author = {Rune Elvik},
keywords = {Daytime running lights},
keywords = {Game theory},
keywords = {Schelling-diagrams},
keywords = {Effects },
abstract = {Abstract Studies that have evaluated the effects on accidents of daytime running lights for cars have consistently found that cars using daytime running lights are involved in fewer multi-party accidents in daylight than cars not using daytime running lights. However, studies evaluating the effects of mandatory use of daytime running lights have not always found an accident reduction. Although findings are mixed, there is a tendency for the aggregate effects of daytime running lights (i.e. the effects of an increasing share of traffic using daytime running lights) to be smaller than the intrinsic effects (i.e. the difference in accident involvement between cars using and not using daytime running lights). This paper presents a game-theoretic model to explain these apparently inconsistent findings. The game-theoretic model is based on so called Schelling-diagrams, originally introduced by Nobel laureate in economics Schelling. The effects of daytime running lights are modelled by means of Schelling-diagrams. It is shown that it is by no means impossible for cars using daytime running lights to always be safer than cars not using daytime running lights, while the total number of accidents remains constant even if the percentage of cars using daytime running lights increases from, say, 10% to 90%. }
}
@article{Elvik2013487,
title = {International transferability of accident modification functions for horizontal curves },
journal = {Accident Analysis & Prevention },
volume = {59},
number = {0},
pages = {487 - 496},
year = {2013},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2013.07.010},
url = {http://www.sciencedirect.com/science/article/pii/S0001457513002789},
author = {Rune Elvik},
keywords = {Horizontal curves},
keywords = {Radius},
keywords = {Accident modification functions},
keywords = {International transferability},
keywords = {Synthesis },
abstract = {Abstract Studies of the relationship between characteristics of horizontal curves and accident rate have been reported in several countries. The characteristic most often studied is the radius of a horizontal curve. Functions describing the relationship between the radius of horizontal curves and accident rate have been developed in Australia, Canada, Denmark, Germany, Great Britain, New Zealand, Norway, Portugal, Sweden, and the United States. Other characteristics of horizontal curves that have been studied include deflection angle, curve length, the presence of transition curves, super-elevation in curves and distance to adjacent curves. This paper assesses the international transferability of mathematical functions (accident modification functions) that have been developed to relate the radius of horizontal curves to their accident rate. The main research problem is whether these functions are similar, which enhances international transferability, or dissimilar, which reduces international transferability. Accident modification functions for horizontal curve radius developed in the countries listed above are synthesised. The sensitivity of the functions to other characteristics of curves than radius is examined. Accident modification functions developed in different countries have important similarities. The functions diverge with respect to accident rate in the sharpest curves. }
}
@article{Elvik2013301,
title = {Can it be true that most drivers are safer than the average driver? },
journal = {Accident Analysis & Prevention },
volume = {59},
number = {0},
pages = {301 - 308},
year = {2013},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2013.06.025},
url = {http://www.sciencedirect.com/science/article/pii/S0001457513002534},
author = {Rune Elvik},
keywords = {Driver safety},
keywords = {Optimism bias},
keywords = {Regression-to-the-mean},
keywords = {Long-term expected number of accidents},
keywords = {Negative binomial distribution },
abstract = {Abstract Surveys finding that a large majority of drivers regard themselves as safer than the average driver have been ridiculed as showing that most drivers are overconfident about their safety and as showing something which is logically impossible, since in a normal distribution exactly half are below average and half above. This paper shows that this criticism is misplaced. Driver accident involvement does not follow a normal distribution, and it is mathematically entirely possible that a huge majority of drivers could be safer than the average driver. The distribution of accidents in a population of drivers is typically skewed, with a majority of drivers not reporting involvement in any accident in the period covered by the data, often a period of 1–3 years. In this paper, examples are given of data sets in which the percentage of drivers who are safer than the average driver ranges from about 70% to 90%. The paper explains how, based on knowing the mean and variance of the distribution of accidents in a population of drivers in a given period, the long-term expected number of accidents for drivers who were involved in 0, 1, 2, or more accidents can be estimated. Such estimates invariably show that the huge majority of drivers are safer than the average driver. }
}
@article{Elvik2013245,
title = {Corrigendum to: “Publication bias and time-trend bias in meta-analysis of bicycle helmet efficacy: A re-analysis of Attewell, Glase and McFadden, 2001” [Accid. Anal. Prev. 43 (2011) 1245–1251] },
journal = {Accident Analysis & Prevention },
volume = {60},
number = {0},
pages = {245 - 253},
year = {2013},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2012.12.003},
url = {http://www.sciencedirect.com/science/article/pii/S0001457512004253},
author = {Rune Elvik},
keywords = {Bicycle helmets},
keywords = {Meta-analysis},
keywords = {Publication bias},
keywords = {Time-trend bias},
keywords = {Re-analysis},
keywords = {Trim-and-fill },
abstract = {Abstract This paper is a corrigendum to the previously published paper: “Publication bias and time-trend bias in meta-analysis of bicycle helmet efficacy: A re-analysis of Attewell, Glase and McFadden, 2001” [Accid. Anal. Prev. (2011) 1245–1251]. This corrigendum was prepared to correct errors in data and analysis in the previously published paper. Like the previously published paper, this paper confirms that the meta-analysis of bicycle helmet efficacy reported by Attewell, Glase and McFadden (Accident Analysis and Prevention, 2001, 345–352) was influenced by publication bias and time-trend bias that was not controlled for. As a result, the analysis reported inflated estimates of the effects of bicycle helmets. This paper presents a re-analysis of the study. The re-analysis included: (1) Ensuring the inclusion of all published studies by means of continuity corrections of estimates of effect relying on zero counts; (2) detecting and adjusting for publication bias by means of the trim-and-fill method; (3) detecting and trying to account for a time-trend bias in estimates of the effects of bicycle helmets; (4) updating the study by including recently published studies evaluating the effects of bicycle helmets. The re-analysis shows smaller safety benefits associated with the use of bicycle helmets than the original study. }
}
@article{Veisten201350,
title = {Valuing casualty risk reductions from estimated baseline risk },
journal = {Research in Transportation Economics },
volume = {43},
number = {1},
pages = {50 - 61},
year = {2013},
note = {The Economics of Transportation Safety },
issn = {0739-8859},
doi = {http://dx.doi.org/10.1016/j.retrec.2012.12.009},
url = {http://www.sciencedirect.com/science/article/pii/S0739885912002132},
author = {Knut Veisten and Stefan Flügel and Luis I. Rizzi and Juan de Dios Ortúzar and Rune Elvik},
keywords = {Fatalities},
keywords = {Injuries},
keywords = {Mixed logit},
keywords = {Stated choice},
keywords = {Value of statistical life},
keywords = {Willingness to pay },
abstract = {Stated choice studies have been applied regularly to the valuation of time savings and other attributes of travelling as perceived by individuals. In such experiments, respondents often provide reference levels for the attributes and the hypothetical choices presented to them are pivoted around actual behaviour. However, most individuals are not able to provide reference levels for the number of casualties on the road they travel. Thus, if valuation of this important element is attempted, it is the researcher who must provide casualty risk reference levels to the respondents. Some studies have applied route choice experiments including a safety attribute but the majority has been limited to only one particular road section with a common baseline risk for all respondents. This study discusses the setting up and results of a more generalized route choice experiment including a safety attribute. Respondents provided, at an initial stage, their travel times and costs related to a recent trip by car. Then, expected numbers of casualties for different trip lengths were calculated based on travel distances and traffic densities. So, the calculated number of severe injuries and fatalities (casualties) per year, on the road section the respondent had travelled, entered as a third attribute in the choices, together with the reported travel times and costs. Route choice was analysed using multinomial logit and mixed logit models. From the latter models we obtained point estimates for the value of the statistical life ranging from € 7.3 million to € 19.1 million. }
}
@article{Elvik2014115,
title = {Challenges of improving safety in very safe transport systems },
journal = {Safety Science },
volume = {63},
number = {0},
pages = {115 - 123},
year = {2014},
note = {},
issn = {0925-7535},
doi = {http://dx.doi.org/10.1016/j.ssci.2013.10.024},
url = {http://www.sciencedirect.com/science/article/pii/S0925753513002579},
author = {Rune Elvik and Nils Gaute Voll},
keywords = {Very safe systems},
keywords = {Railways},
keywords = {Norway},
keywords = {Challenges },
abstract = {Abstract This paper discusses some challenges that may arise when trying to improve safety in systems that are already very safe. Railways in Norway are used as a case of a very safe transport system. The following challenges in improving safety are discussed: (1) A low number of accidents per unit of time makes it difficult to estimate both the current level of accident risk and changes over time in the level of accident risk. (2) Partly as a result of the low number of accidents, incident reporting has been introduced; however it is not always clear how to interpret changes in the number of incidents reported. One reason for this is that some incidents have a low potential for developing into accidents, because multiple safety barriers (defences-in-depth) stop incidents from escalating. (3) Knowledge of the effectiveness of safety barriers combined with a good safety record may lead to excessive reliance on the safety barriers and behavioural adaptation to them. The existence of these challenges is illustrated by means of data from Norwegian railways. It is discussed whether attaining a very high level of safety may lead to loss of information and loss of motivation that may slow down further progress in improving safety. }
}
@article{Elvik2011751,
title = {Anders af Wåhlberg: Driver Behaviour and Accident Research Methodology. Unresolved Problems. Ashgate Publishing (2009). 280 pp. ISBN:978-0-7546-7076-6 },
journal = {Safety Science },
volume = {49},
number = {5},
pages = {751 - 752},
year = {2011},
note = {},
issn = {0925-7535},
doi = {http://dx.doi.org/10.1016/j.ssci.2011.01.011},
url = {http://www.sciencedirect.com/science/article/pii/S0925753511000191},
author = {Rune Elvik}
}
@article{Elvik2013854,
title = {A re-parameterisation of the Power Model of the relationship between the speed of traffic and the number of accidents and accident victims },
journal = {Accident Analysis & Prevention },
volume = {50},
number = {0},
pages = {854 - 860},
year = {2013},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2012.07.012},
url = {http://www.sciencedirect.com/science/article/pii/S0001457512002667},
author = {Rune Elvik},
keywords = {Speed of traffic},
keywords = {Traffic accidents},
keywords = {Mathematical models},
keywords = {Power Model},
keywords = {Exponential function },
abstract = {This paper presents a re-analysis of the Power Model of the relationship between the mean speed of traffic and road safety. Past evaluations of the model, most recently in 2009, have broadly speaking supported it. However, the most recent evaluation of the model indicated that the relationship between speed and road safety depends not only on the relative change in speed, as suggested by the Power Model, but also on initial speed. This implies that the exponent describing, for example, a 25% reduction in speed will not be the same when speed changes from 100 km/h to 75 km/h as it will when speed changes from 20 km/h to 15 km/h. This paper reports an analysis leading to a re-parameterisation of the Power Model in terms of continuously varying exponents which depend on initial speed. The re-parameterisation was accomplished by fitting exponential functions to data points in which changes in speed and accidents were sorted in groups of 10 km/h according to initial speed, starting with data points referring to the highest initial speeds. The exponential functions fitted the data extremely well and imply that the effect on accidents of a given relative change in speed is largest when initial speed is highest. }
}
@incollection{Elvik2011471,
title = {Chapter 33 - Public Policy },
editor = {Porter, Bryan E. },
booktitle = {Handbook of Traffic Psychology },
publisher = {Academic Press},
edition = {},
address = {San Diego},
year = {2011},
pages = {471 - 483},
isbn = {978-0-12-381984-0},
doi = {http://dx.doi.org/10.1016/B978-0-12-381984-0.10033-5},
url = {http://www.sciencedirect.com/science/article/pii/B9780123819840100335},
author = {Rune Elvik},
abstract = {Publisher Summary Public policy refers to any action taken by public bodies to influence highway safety. The first stage of policy development is to find out what the problem is and identify factors that contribute to it. The next stage is to develop targets for improving safety and decide on whether these targets should be quantified or not. Once the ambitions for improving safety have been defined, a broad survey of potentially effective safety measures is needed to identify those measures that can make the largest contribution to reducing the number of fatalities and injuries. However, for various reasons, it may not be possible to introduce all effective safety measures; an explicit consideration of constraints on safety policy can help in developing realistic policy options. There will very often be more than one safety measures that can address a given safety problem; hence, developing alternative policy options that can be compared is instructive. A key activity in policy development is to estimate the expected effects of safety measures on the number of accidents or the number of killed or injured road users. These estimates should ideally be based on the best available knowledge regarding the effects on safety of various measures. Any prediction of the safety effects of a program will be uncertain, and it may be useful to explicitly consider sources of uncertainty and how to reduce uncertainty. Policy is always made within constraints that are not necessarily chosen or wanted by policy makers; usually, therefore, several considerations are relevant for policy choice, requiring complex trade-offs. Once it has been decided to implement a set of safety measures, the effects of these measures should be evaluated to increase knowledge of their effects for use in future policy making. This chapter reviews the contribution that traffic psychology can make to public policy designed to improve road safety. The stages of policy development in which traffic psychology can contribute are identified. The most important contributions of traffic psychology to public policy include (1) identifying road user behavior that contributes to accidents and developing ways to influence such behavior; (2) promoting the use of an experimental study design when evaluating the effects of road safety measures; (3) helping develop designs of vehicles, roads, and traffic control devices that are adapted to human capabilities; (4) predicting if behavioral adaptation to new safety measures is likely to occur or not; and (5) acting to correct a tendency toward wishful thinking that may develop among policy makers who may base policy on an overly idealistic approach to how road safety can be improved. Examples are given of all these types of contributions of traffic psychology. }
}
@article{Elvik2012272,
title = {The range of replications technique for assessing the external validity of road safety evaluation studies },
journal = {Accident Analysis & Prevention },
volume = {45},
number = {0},
pages = {272 - 280},
year = {2012},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2011.07.016},
url = {http://www.sciencedirect.com/science/article/pii/S0001457511002132},
author = {Rune Elvik},
keywords = {External validity},
keywords = {Road safety evaluation studies},
keywords = {Range of replications},
keywords = {Consistency score},
keywords = {Time trend in findings},
keywords = {Accident modification function },
abstract = {This paper introduces a simple statistical technique that can be used to assess the external validity of road safety evaluation studies. External validity refers to the possibility of generalising the results of research to other contexts than those in which it was made. There are several aspects of external validity. Two aspects that are often of interest concern the applicability of the results of road safety evaluation studies across countries and time. Can the results of studies made in one or more countries be applied in countries where studies have not been made? Can the results of studies made many years ago still be applied? The technique introduced in this paper is designed to provide support in answering these questions. The technique evaluates the stability of research results in time and space. The technique is based on cumulative meta-analysis and produces statistics that show the consistency of study results in time and space (across countries). The range of replications denotes the span of time and countries in which studies have been made. The idea is that if the results of studies are stable throughout the range of replications, one may have greater confidence in their external validity than if the results of research vary in time and between countries. The technique is illustrated by means of numerical examples. }
}
@incollection{Anderson2011ix,
title = {List of Contributors },
editor = {Porter, Bryan E. },
booktitle = {Handbook of Traffic Psychology },
publisher = {Academic Press},
edition = {},
address = {San Diego},
year = {2011},
pages = {ix - x},
isbn = {978-0-12-381984-0},
doi = {http://dx.doi.org/10.1016/B978-0-12-381984-0.10040-2},
url = {http://www.sciencedirect.com/science/article/pii/B9780123819840100402},
author = {David S. Anderson and Thomas D. Berry and Oliver Carsten and David Crundall and Ann M. Dellinger and Krystall Dunaway and David W. Eby and Rune Elvik and Barbara Freund and Ray Fuller and A. Ian Glendon and John A. Groeger and Charlene Hallett and Dwight Hennessy and Kati Hernetkoski and Martha Híjar and David J. Houston and Patty Huang and Cristina Inclán-Valadez and A. Hamish Jamson and Kristie L. Johnson and Esko Keskinen and Sheila G. Klauer and Young-Jun Kweon and Timo Lajunen and Kevin J. Manning and Jennifer F. May and Julie McClafferty and Rebecca B. Naumann and Ilit Oppenheim and Türker Özkan and Karl Peltzer and Miguel Perez and Ricardo Pérez-Núñez and Bryan E. Porter and Michael A. Regan and Richard Retting and Tova Rosenbloom and Cynthia Shier Sabo and Maria T. Schultheis and David Shinar and David A. Sleet and Paula Smith and Stephen G. Stradling and Joanne E. Taylor and Geoffrey Underwood and Ron Van Houten and Jonathon M. Vivoda and Ian Walker and Kelli England Will and Flaura Koplin Winston}
}
@article{Elvik2012146,
title = {Assessing the efficiency of priorities for traffic law enforcement in Norway },
journal = {Accident Analysis & Prevention },
volume = {47},
number = {0},
pages = {146 - 152},
year = {2012},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2012.01.017},
url = {http://www.sciencedirect.com/science/article/pii/S0001457512000309},
author = {Rune Elvik and Céline Vallet Sogge and Lasse Lager and Finn Harald Amundsen and Live Tanum Pasnin and Runar Karlsen and Knut Fosli},
keywords = {Police enforcement},
keywords = {Traffic violations},
keywords = {Attributable risk},
keywords = {Efficiency},
keywords = {Cost-benefit analysis },
abstract = {This paper assesses the efficiency of priorities for traffic law enforcement in Norway. Priorities are regarded as efficient if: (1) enforcement ensures a sufficient level of deterrence to keep down the rate of violations; (2) selection of target violations for enforcement is based on the risk attributable to them; and (3) an optimal level of enforcement is selected, i.e. the marginal benefits of enforcement in terms of preventing accidents equal the marginal costs of enforcement. The efficiency of current traffic law enforcement in Norway is assessed in terms of these criteria. It is found that the risk of apprehension varies considerably between different traffic violations. These variations do not reflect the risk attributable to the violations, i.e. it is not the case that the risk of apprehension is higher for violations that make a large contribution to fatalities and injuries than for violations that make a smaller contribution. In principle, shifting priorities so as to increase the risk of apprehension for some violations and reduce it for other violations could make police enforcement slightly more efficient. The main finding, however, is that the current level of enforcement is too low. Cost-benefit analyses show that substantially increasing the amount of police enforcement is cost-effective. }
}
@article{VanElslande20121,
title = {Powered two-wheelers within the traffic system },
journal = {Accident Analysis & Prevention },
volume = {49},
number = {0},
pages = {1 - 4},
year = {2012},
note = {\{PTW\} + Cognitive impairment and Driving Safety },
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2012.09.007},
url = {http://www.sciencedirect.com/science/article/pii/S0001457512003144},
author = {Pierre Van Elslande and Rune Elvik},
abstract = {The world of powered two-wheelers has changed dramatically in recent decades, along with a steady increase in the number and diversity of the fleet and uses. This evolution has led to some benefits in terms of mobility, but also some drawbacks in terms of safety. The problems involved are neither simple nor monolithic and there is a lack of knowledge about their different facets and backgrounds that require research work both in terms of risk exposure, accidents factors and impact severity. This special issue of Accident Analysis and Prevention regroups 30 papers devoted to an improvement in this knowledge, exploring the different aspects involved in the safety of powered two-wheelers by complementary methods. }
}
@article{Elvik2012173,
title = {Analytic choices in road safety evaluation: Exploring second-best approaches },
journal = {Accident Analysis & Prevention },
volume = {45},
number = {0},
pages = {173 - 179},
year = {2012},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2011.12.006},
url = {http://www.sciencedirect.com/science/article/pii/S0001457511003344},
author = {Rune Elvik},
keywords = {Road safety},
keywords = {Evaluation study},
keywords = {Second best approach},
keywords = {Empirical Bayes approach},
keywords = {Methodological study },
abstract = {Conducting rigorous before-and-after studies is essential for improving knowledge regarding the effects of road safety measures. However, state-of-the-art approaches like the empirical Bayes or fully Bayesian techniques cannot always be applied, as the data required by these approaches may be missing or unreliable. The choice facing researchers in such a situation is to either apply “second-best” approaches or abstain from doing an evaluation study. An objection to applying second-best approaches is that these approaches do not control as well for confounding factors as state-of-the-art approaches. This paper explores the implications of choice of study design by examining how the findings of several evaluation studies made in Norway depend on choices made with respect to:1. Using the empirical Bayes approach versus using simpler approaches; 2. Use or non-use of a comparison group; 3. The choice of comparison group when there is more than one candidate. It is found that the choices made with respect to these points can greatly influence the estimates of safety effects in before-and-after studies. Two second-best techniques (i.e. techniques other than the empirical Bayes approach) for controlling for confounding factors were tested. The techniques were found not to produce unbiased estimates of effect and their use is therefore discouraged. }
}
@article{Elvik2011920,
title = {Developing an accident modification function for speed enforcement },
journal = {Safety Science },
volume = {49},
number = {6},
pages = {920 - 925},
year = {2011},
note = {},
issn = {0925-7535},
doi = {http://dx.doi.org/10.1016/j.ssci.2011.02.016},
url = {http://www.sciencedirect.com/science/article/pii/S0925753511000695},
author = {Rune Elvik},
keywords = {Enforcement},
keywords = {Accidents},
keywords = {Systematic review},
keywords = {Accident modification function },
abstract = {This paper presents an accident modification function for speed enforcement. The function describes the percentage effect of enforcement on the number of injury accidents as a function of the relative change in the amount of enforcement. Thirteen studies that have evaluated the effects of different levels of enforcement, each containing between four and eight data points, were used as data source. A hypothesis regarding the shape of an accident modification function was formulated to help assess the plausibility of the estimated relationships. In the first stage of analysis, functions were fitted to the data points of each study by means of weighted regression analysis. Many of these functions were highly implausible and likely to be influenced by outlying data points and random variation. In the second stage of analysis, data from all studies except two were pooled and data points referring to identical or almost identical levels of enforcement were aggregated to reduce the influence of random variation. The number of data points was thus reduced from 63 to 15 and an accident modification function was fitted to the data points. The function was consistent with the hypothesis guiding the study. }
}
@article{Elvik20112047,
title = {A framework for a critical assessment of the quality of epidemiological studies of driver health and accident risk },
journal = {Accident Analysis & Prevention },
volume = {43},
number = {6},
pages = {2047 - 2052},
year = {2011},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2011.05.024},
url = {http://www.sciencedirect.com/science/article/pii/S0001457511001436},
author = {Rune Elvik},
keywords = {Driver health},
keywords = {Epidemiological studies},
keywords = {Error},
keywords = {Bias},
keywords = {Confounding},
keywords = {Critical assessment },
abstract = {A large number of studies have tried to assess how various aspects of driver health influence driver involvement in accidents. The objective of this paper is to provide a framework for a critical assessment of the quality these studies from a methodological point of view. Examples are given of how various sources of bias and confounding can produce study findings that are highly misleading. Ten potential sources of error and bias in epidemiological studies of the contribution of driver health impairments to road accidents are discussed:(1) Poor description of the medical conditions whose effects are studied (measurement error). (2) Inadequate control for the effects of exposure on accident rate. (3) Sampling endogeneity with respect to assessment for fitness to drive (outcome-based sampling; self-selection bias). (4) Combined exposure to several risk factors. (5) Poor control for potentially confounding factors. (6) Failure to specify potentially moderating factors (interaction effects). (7) Failure to consider a severity gradient with respect to the effect of health impairments. (8) Failure to specify the compliance of drivers with medical treatments or treatment effectiveness. (9) No data on the population prevalence of various health conditions. (10) The use of multiple study approaches and methods making the comparison and synthesis of findings difficult. Examples are given of how all these items may influence the findings of a single study or make synthesising findings from multiple studies difficult. A checklist for assessing study quality is provided. }
}
@article{Elvik20111245,
title = {Publication bias and time-trend bias in meta-analysis of bicycle helmet efficacy: A re-analysis of Attewell, Glase and McFadden, 2001 },
journal = {Accident Analysis & Prevention },
volume = {43},
number = {3},
pages = {1245 - 1251},
year = {2011},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2011.01.007},
url = {http://www.sciencedirect.com/science/article/pii/S000145751100008X},
author = {Rune Elvik},
keywords = {Bicycle helmets},
keywords = {Meta-analysis},
keywords = {Publication bias},
keywords = {Time-trend bias},
keywords = {Re-analysis},
keywords = {Trim-and-fill },
abstract = {This paper shows that the meta-analysis of bicycle helmet efficacy reported by Attewell, Glase, and McFadden (Accident Analysis and Prevention 2001, 345–352) was influenced by publication bias and time-trend bias that was not controlled for. As a result, the analysis reported inflated estimates of the effects of bicycle helmets. This paper presents a re-analysis of the study. The re-analysis included: (1) detecting and adjusting for publication bias by means of the trim-and-fill method; (2) ensuring the inclusion of all published studies by means of continuity corrections of estimates of effect rely on zero counts; (3) detecting and trying to account for a time-trend bias in estimates of the effects of bicycle helmets; (4) updating the study by including recently published studies evaluating the effects of bicycle helmets. The re-analysis shows smaller safety benefits associated with the use of bicycle helmets than the original study. }
}
@article{Elvik20081115,
title = {Road safety management by objectives: A critical analysis of the Norwegian approach },
journal = {Accident Analysis & Prevention },
volume = {40},
number = {3},
pages = {1115 - 1122},
year = {2008},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2007.12.002},
url = {http://www.sciencedirect.com/science/article/pii/S0001457507002151},
author = {Rune Elvik},
keywords = {Road safety},
keywords = {Quantified targets},
keywords = {Management by objectives},
keywords = {Effectiveness},
keywords = {Policy analysis },
abstract = {The Norwegian Public Roads Administration has developed a comprehensive system of road safety management by objectives. A broad set of objectives regarding road user behaviour, vehicle safety standards and the safety of roads has been formulated as part of the National Transport Plan for the term 2010–2019. These objectives have been derived from an overall objective of reducing the number of killed or seriously injured road users by 50% before the year 2020. This paper describes the system and provides a critical analysis of it. Factors that influence the effectiveness of management by objectives are identified. It is concluded that while the system of management by objectives developed in Norway has a number of attractive characteristics it also has a number of weak points that may limit its effectiveness. It is therefore by no means certain that the objective of reducing fatalities and serious injuries by 50% will be realised. }
}
@article{Elvik20102171,
title = {Sources of uncertainty in estimated benefits of road safety programmes },
journal = {Accident Analysis & Prevention },
volume = {42},
number = {6},
pages = {2171 - 2178},
year = {2010},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2010.03.022},
url = {http://www.sciencedirect.com/science/article/pii/S0001457510001053},
author = {Rune Elvik},
keywords = {Road safety programme},
keywords = {Estimates of effect},
keywords = {Uncertainty},
keywords = {Propagation of errors },
abstract = {National road safety programmes have been developed in many motorised countries. Some of these programmes contain estimates of the safety benefits that were expected to be realised if the programmes were fully implemented. When these estimates are compared to actual outcomes, it is not uncommon to find large differences. This paper argues that differences between the predicted and actual results of road safety programmes could be the result of a large, but generally unrecognised, uncertainty inherent in estimates of the effects of such programmes. Ten sources of uncertainty are identified and briefly described. The possibility of describing these sources of uncertainty numerically, and of estimating their joint contribution, is discussed. It is concluded that at the current state of knowledge, it is not possible to meaningfully estimate the total uncertainty inherent in road safety programmes. The prospects of reducing uncertainty by means of research are discussed. }
}
@article{Elvik20101189,
title = {Strengthening incentives for efficient road safety policy priorities: The roles of cost–benefit analysis and road pricing },
journal = {Safety Science },
volume = {48},
number = {9},
pages = {1189 - 1196},
year = {2010},
note = {Scientific Research on Road Safety Management },
issn = {0925-7535},
doi = {http://dx.doi.org/10.1016/j.ssci.2010.01.005},
url = {http://www.sciencedirect.com/science/article/pii/S092575351000010X},
author = {Rune Elvik},
keywords = {Cost-benefit analysis},
keywords = {Power},
keywords = {Welfare},
keywords = {Incentives},
keywords = {Road safety policy},
keywords = {Social dilemmas },
abstract = {This paper discusses how incentives for setting efficient priorities in road safety policy can be strengthened. Efficient priorities are characterised by the use of cost-effective road safety measures. Cost-effective road safety measures can be identified by means of cost-benefit analyses. Studies of the actual priorities in road safety policy, in particular in the Scandinavian countries, suggest that these priorities are inefficient, i.e. characterised by the non-use or sub-optimal use of cost-effective road safety measures as well as an extensive use of ineffective road safety measures. This occurs despite the fact that road safety policy analyses have included extensive cost-benefit analyses of road safety measures. It would thus appear that cost-benefit analyses do not necessarily generate a sufficient incentive to implement cost-effective road safety measures. Possible reasons for this are discussed in the paper. It is argued that a large part of the monetary benefits of road safety measures, as estimated in cost-benefit analyses, are not subject to market transactions, and do therefore not manifest themselves in the form of increased income or higher profits. While cost-benefit analyses are indispensable as a means of identifying cost-effective road safety measures, their influence on actual road safety policy needs to be strengthened by providing additional incentives for the use of cost-effective road safety measures. It is suggested that a system of road pricing could generate such incentives. A brief sketch of a hypothetical system of road pricing is given and some problems associated with the implementation of this system are discussed. }
}
@article{Elvik2011253,
title = {Assessing causality in multivariate accident models },
journal = {Accident Analysis & Prevention },
volume = {43},
number = {1},
pages = {253 - 264},
year = {2011},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2010.08.018},
url = {http://www.sciencedirect.com/science/article/pii/S0001457510002514},
author = {Rune Elvik},
keywords = {Causality},
keywords = {Accident prediction models},
keywords = {Criteria},
keywords = {Assessment },
abstract = {This paper discusses the application of operational criteria of causality to multivariate statistical models developed to identify sources of systematic variation in accident counts, in particular the effects of variables representing safety treatments. Nine criteria of causality serving as the basis for the discussion have been developed. The criteria resemble criteria that have been widely used in epidemiology. To assess whether the coefficients estimated in a multivariate accident prediction model represent causal relationships or are non-causal statistical associations, all criteria of causality are relevant, but the most important criterion is how well a model controls for potentially confounding factors. Examples are given to show how the criteria of causality can be applied to multivariate accident prediction models in order to assess the relationships included in these models. It will often be the case that some of the relationships included in a model can reasonably be treated as causal, whereas for others such an interpretation is less supported. The criteria of causality are indicative only and cannot provide a basis for stringent logical proof of causality. }
}
@article{Elvik20081830,
title = {A survey of operational definitions of hazardous road locations in some European countries },
journal = {Accident Analysis & Prevention },
volume = {40},
number = {6},
pages = {1830 - 1835},
year = {2008},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2008.08.001},
url = {http://www.sciencedirect.com/science/article/pii/S0001457508001310},
author = {Rune Elvik},
keywords = {Hazardous road locations},
keywords = {Operational definition},
keywords = {State-of-the-art approach},
keywords = {Survey},
keywords = {European countries },
abstract = {This paper presents the results of a survey of operational definitions of hazardous road locations in some European countries. The term operational definition refers to the criteria and methods used to identify hazardous road locations. Eight countries were included in the survey. The operational definitions of hazardous road locations used in these countries were compared in terms of six characteristics:1. Whether hazardous road locations are identified by reference to a population of similar sites, i.e. by means of sampling from a predefined list of sites or identified without referring to any population of sites. 2. Whether a sliding window method is used to identify hazardous road locations. 3. Whether hazardous road locations are identified in terms of deviance from a normal level of safety or without reference to a normal level of safety. 4. Whether hazardous road locations are identified in terms of the recorded or expected number of accidents. 5. Whether accident severity is considered in identifying hazardous road locations or not. 6. The length of the period used to identify hazardous road locations. Most operational definitions of hazardous road locations were found: (1) not to refer to any population of similar sites, (2) to rely on a sliding window approach, and (3) identify hazardous road locations in terms of the recorded number of accidents. In four of the countries, hazardous road locations are identified as sites that have significantly more accidents than the normal number. Accident severity was considered in four of the countries. The period used to identify hazardous road locations varied between 1 and 5 years. Compared to state-of-the-art techniques for identifying hazardous road locations, most of the approaches used in the countries surveyed were primitive and are likely to involve substantial inaccuracies. Steps that can be taken to bring practice closer to the state-of-the-art are outlined. }
}
@article{Elvik2007689,
title = {The deterrent effect of increasing fixed penalties for traffic offences: The Norwegian experience },
journal = {Journal of Safety Research },
volume = {38},
number = {6},
pages = {689 - 695},
year = {2007},
note = {},
issn = {0022-4375},
doi = {http://dx.doi.org/10.1016/j.jsr.2007.09.007},
url = {http://www.sciencedirect.com/science/article/pii/S0022437507001272},
author = {Rune Elvik and Peter Christensen},
keywords = {Fixed penalty},
keywords = {Deterrence},
keywords = {Evaluation study },
abstract = {Problem Many motorized countries use fixed penalties to deter the most common traffic violations. Fixed penalties are usually given at the spot by a police officer. If the offender accepts the fixed penalty, no court hearing or trial is held. During the years 1995–2004, the rates for fixed penalties for traffic offences in Norway increased substantially. This paper evaluates the effects on compliance of these increases. Method Regression analysis was performed to determine the effects of increases in fixed penalties. Results For speeding in general, no effect of increasing fixed penalties can be found. For speeding close to speed camera sites, there is a weak tendency for the violation rate to go down. This tendency is not statistically significant at conventional levels. For seat belt wearing, wearing rates are found to increase as fixed penalties have increased. In recent years, however, enforcement of the seat belt law has stepped up, making it impossible to separate the effect of enforcement from that of fixed penalties. Impact on industry It has been suggested that the police may adapt to stricter penalties by reducing enforcement or by adopting larger tolerance margins for violations. Available evidence does not support this hypothesis. }
}
@article{Elvik2009817,
title = {The trade-off between efficiency and equity in road safety policy },
journal = {Safety Science },
volume = {47},
number = {6},
pages = {817 - 825},
year = {2009},
note = {Occupational Accidents and Safety: The Challenge of Globalization / Resolving multiple criteria in decision-making involving risk of accidental loss },
issn = {0925-7535},
doi = {http://dx.doi.org/10.1016/j.ssci.2008.10.012},
url = {http://www.sciencedirect.com/science/article/pii/S0925753508001835},
author = {Rune Elvik},
keywords = {Efficiency},
keywords = {Equity},
keywords = {Road safety policy},
keywords = {Trade-off},
keywords = {John Rawls’ principles of justice },
abstract = {This paper discusses the relationship between efficiency and equity as objectives of road safety policy. The term efficiency refers to the efficient use of all road safety measures. Road safety measures are used efficiently if the priority given to them is based on the criterion that marginal social benefits should be at least equal to marginal social costs. To use road safety measures efficiently therefore means that the priority given to each measure is set strictly according to cost–benefit analyses. Thus, the main question discussed in this paper is whether setting priorities for safety measures strictly according to cost–benefit analyses will produce results that are regarded as equitable and fair. The notions of equity and fairness do not have any universally accepted definitions. In the paper, an attempt is made to apply John Rawls’ difference principle as a criterion of fairness with respect to the distribution of risk. The distribution of risk is examined along several dimensions: between groups of road users, between regions, between social groups, and with respect to the relationship between who pays for a road safety measure and who benefits from it. It is concluded that there is a conflict between efficiency and equity as far as the provision of road safety is concerned. Promoting greater equity requires a departure from efficiency, as defined in economic welfare theory, as the only criterion for setting policy priorities. }
}
@article{Elvik20081964,
title = {The predictive validity of empirical Bayes estimates of road safety },
journal = {Accident Analysis & Prevention },
volume = {40},
number = {6},
pages = {1964 - 1969},
year = {2008},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2008.07.007},
url = {http://www.sciencedirect.com/science/article/pii/S0001457508001528},
author = {Rune Elvik},
keywords = {Road safety},
keywords = {Before-and-after study},
keywords = {Accident prediction},
keywords = {Empirical Bayes method},
keywords = {Test },
abstract = {This paper examines the predictive validity of empirical Bayes (EB) estimates of road safety. The predictive performance of EB-estimates was tested by applying five versions of EB-estimates of road safety:(1) A simple estimate derived from the empirical distribution of accidents in a population of sites, by which the number of accidents predicted for period 2 for sites that recorded k accidents in period 1 equals the number of accidents for sites that recorded k + 1 accidents in period 1. (2) Estimates derived from the parameters of a negative binomial distribution fitted to an empirical distribution of accidents in a population of sites by means of the method of moments. (3) Estimates derived from the parameters of a negative binomial distribution fitted to an empirical distribution of accidents in a population of sites by means of the maximum likelihood technique. (4) Estimates derived by combining the predictions of an accident prediction model and the recorded number of accidents for a site. (5) Estimates derived by combining the predictions of a different version of an accident prediction model and the recorded number of accidents for a site. All versions of EB-estimates are compared to the traditional, naïve assumption of treating the recorded number of accidents as an unbiased estimate of the expected number of accidents. To test the predictive performance of EB-estimates, data for two periods was used. EB-estimates based on data for the first period were treated as predictions of the number of accidents in the second period for road sections that had 0, 1, 2, etc., accidents in the first period, the idea being that the more accurate the prediction, the more accurate the result of a before-and-after study. All versions of EB-estimates were found to give considerably more correct predictions of the number of accidents in the second period than relying on the count of accidents in the first period as a prediction of the count in the second period. Smaller prediction errors were associated with predictions based on accident prediction models than predictions not based on such models. }
}
@article{Elvik20101089,
title = {Why some road safety problems are more difficult to solve than others },
journal = {Accident Analysis & Prevention },
volume = {42},
number = {4},
pages = {1089 - 1096},
year = {2010},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2009.12.020},
url = {http://www.sciencedirect.com/science/article/pii/S0001457509003340},
author = {Rune Elvik},
keywords = {Road safety problem},
keywords = {Incompatibility},
keywords = {Unprotected road users},
keywords = {Risk factors},
keywords = {Solution },
abstract = {Some road safety problems have persisted for a long time in nearly all motorised countries, suggesting that they are not easily solved. This paper documents the persistence over time of five such problems: the high risk of accidents involving young drivers; the high risk of injury run by unprotected road users; risks attributable to incompatibility between different types of vehicles and groups of road users; differences in risk between different types of traffic environment and speeding. A taxonomy of road safety problems is developed in order to identify characteristics of problems that can make them difficult to solve. It is argued that if a problem is not perceived as a problem, is attributable to a misguided confidence in road user rationality, involves social dilemmas, or is closely related to the physics of impacts then it is likely to be difficult to solve. Problems to which biological factors contribute are also likely to be difficult to solve. The characteristics that can make a problem difficult to solve are to some extent present for all the five problems shown to be persistent in this paper. }
}
@article{Elvik20081200,
title = {Dimensions of road safety problems and their measurement },
journal = {Accident Analysis & Prevention },
volume = {40},
number = {3},
pages = {1200 - 1210},
year = {2008},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2008.01.004},
url = {http://www.sciencedirect.com/science/article/pii/S0001457508000109},
author = {Rune Elvik},
keywords = {Road safety problem},
keywords = {Dimension},
keywords = {Numerical measurement},
keywords = {Selection for treatment },
abstract = {This paper identifies nine characteristics of road safety problems that are all in principle amenable to numerical measurement. The nine characteristics identified are:1. Magnitude 2. Severity 3. Externality 4. Inequity 5. Complexity 6. Spatial dispersion 7. Temporal stability 8. Perceived urgency 9. Amenability to treatment The purpose of identifying these dimensions and of trying to measure them is to provide a basis for selecting problems for treatment by means of safety programmes. Selecting problems for treatment usually cannot be done on the basis of a single dimension, as it is the mix of characteristics that determine the prospects for successfully treating a problem. It is proposed that amenability to treatment is a function of complexity, perceived urgency and the availability of cost-effective treatments. Speed and speeding is used as an example of a road safety problem to illustrate how the various dimensions can be measured. }
}
@article{Elvik2010245,
title = {The stability of long-term trends in the number of traffic fatalities in a sample of highly motorised countries },
journal = {Accident Analysis & Prevention },
volume = {42},
number = {1},
pages = {245 - 260},
year = {2010},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2009.08.002},
url = {http://www.sciencedirect.com/science/article/pii/S0001457509002085},
author = {Rune Elvik},
keywords = {Traffic fatalities},
keywords = {Long-term trends},
keywords = {Stability},
keywords = {Prediction },
abstract = {This paper examines the stability of long-term trends in the number of traffic fatalities in eight highly motorised countries: Norway, Sweden, Denmark, Finland, The Netherlands, Great Britain, Australia and The United States. In all these countries, the number of traffic fatalities reached a peak around 1970–1972 and has since declined. The decline has, however, been irregular and fairly long periods of stagnation or even increase in the number of fatalities have occurred in all countries. A stable trend is defined in this paper as a trend that remains unchanged and therefore can be used to successfully predict the future number of fatalities by means of extrapolation. It is concluded that the trends towards fewer fatalities in the countries selected have not been stable and that even trend lines that fit past trends very closely are usually worthless for predictive purposes. An attempt was made to identify factors influencing long-term trends by fitting negative binomial regression models to fatality data. Although some of the models fitted the data marginally better than simple trend lines, these models are not necessarily more useful for predicting future trends than simple trend lines, since using the models for prediction requires that future changes in all explanatory variables must be predicted. The chief lesson is that past trends do not provide a reliable basis for predicting future developments with respect to the number of traffic fatalities. }
}
@article{Veisten20071162,
title = {Total costs of bicycle injuries in Norway: Correcting injury figures and indicating data needs },
journal = {Accident Analysis & Prevention },
volume = {39},
number = {6},
pages = {1162 - 1169},
year = {2007},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2007.03.002},
url = {http://www.sciencedirect.com/science/article/pii/S0001457507000358},
author = {Knut Veisten and Kjartan Sælensminde and Kari Alvær and Torkel Bjørnskau and Rune Elvik and Trude Schistad and Børge Ytterstad},
keywords = {Bicycle accidents},
keywords = {Costs},
keywords = {Hospital data},
keywords = {Injury severity},
keywords = {Official data},
keywords = {Underreporting },
abstract = {Bicycle injuries and fatalities are reported by the police to Statistics Norway. Fatality records from the police are then corrected with Vital Statistics records. However, there is no complete hospital recording that could provide more correct data for bicycle injuries. Bicycle injuries are underreported in official data. There is a nearly complete omission of single bicycle accidents. This disguises societal accident costs and curtails the identification of black spots and effective infrastructure improvements. This paper provides an estimate of total bicycle injuries in Norway and the total costs of these injuries. Application of case study hospital data from Norwegian towns enabled an estimation of the relationship between these data and the official data, including the distribution of injuries by severity. Costs were then assessed by applying official monetary values for given levels of injury severity. Total annual bicycle injury costs are huge, but these costs must be balanced against the benefits of bicycling, related to health and environment. Accident reporting and data should be enhanced to enable a reduction of bicycle injuries. }
}
@article{Elvik2009849,
title = {The non-linearity of risk and the promotion of environmentally sustainable transport },
journal = {Accident Analysis & Prevention },
volume = {41},
number = {4},
pages = {849 - 855},
year = {2009},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2009.04.009},
url = {http://www.sciencedirect.com/science/article/pii/S0001457509000876},
author = {Rune Elvik},
keywords = {Pedestrians},
keywords = {Cyclists},
keywords = {Risks},
keywords = {Non-linearity},
keywords = {Transfer of trips},
keywords = {Environmentally sustainable transport },
abstract = {Several studies show that the risks of injury to pedestrians and cyclists are highly non-linear. This means that the more pedestrians or cyclists there are, the lower is the risk faced by each pedestrian or cyclist. On the other hand, the more motor vehicles there are, the higher becomes the risk faced by each pedestrian or cyclist. The relationships found in previous studies suggest that if very large transfers of trips from motor vehicles to walking or cycling take place, the total number of accidents may be reduced. The “safety in numbers” effect for pedestrians and cyclists would then combine favourably with the effect of a lower number of motor vehicles to produce a lower total number of accidents. This paper explores if such an effect is possible, relying on the findings of studies that show the non-linearity of injury risks for pedestrians and cyclists. It is found that for very large transfers of trips from motor vehicles to walking or cycling, a reduction of the total number of accidents is indeed possible. This shows that the high injury rate for pedestrians and cyclists in the current transport system does not necessarily imply that encouraging walking or cycling rather than driving will lead to more accidents. }
}
@article{Elvik2010196,
title = {A restatement of the case for speed limits },
journal = {Transport Policy },
volume = {17},
number = {3},
pages = {196 - 204},
year = {2010},
note = {},
issn = {0967-070X},
doi = {http://dx.doi.org/10.1016/j.tranpol.2009.12.006},
url = {http://www.sciencedirect.com/science/article/pii/S0967070X10000181},
author = {Rune Elvik},
keywords = {Rationality},
keywords = {Speed choice},
keywords = {Speed limits},
keywords = {Subjective},
keywords = {Objective },
abstract = {This paper provides a restatement of the case for speed limits. The paper argues that driver speed choice cannot be granted any normative status (i.e. be regarded as optimal from a societal point of view) unless it is “objectively” rational, even if it can be reasonably interpreted as “subjectively” rational. A distinction between “subjective” and “objective” rationality is very rarely made in modern analyses relying on the theory of rational choice, but it makes sense with respect to the choice of speed. Studies that have assessed which impacts of speed drivers consider, whether drivers correctly assess these impacts, and how drivers coordinate their choice of speed with other drivers are reviewed. It is concluded that driver speed choice is not “objectively” rational. It is concluded that the lack of rationality in driver speed choice implies that this choice needs to be regulated by means of speed limits. }
}
@article{Elvik2009387,
title = {Costs and benefits to Sweden of Swedish road safety research },
journal = {Accident Analysis & Prevention },
volume = {41},
number = {3},
pages = {387 - 392},
year = {2009},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2008.12.009},
url = {http://www.sciencedirect.com/science/article/pii/S0001457508002406},
author = {Rune Elvik and Marika Kolbenstvedt and Beate Elvebakk and Arild Hervik and Lasse Bræin},
keywords = {Road safety},
keywords = {Research},
keywords = {Evaluation study},
keywords = {Sweden},
keywords = {Long-term trends },
abstract = {This paper summarises a study designed to answer the following question: what are the benefits to Swedish society of road safety research in Sweden funded by the Swedish Transport Research Council and the programme for vehicle safety research during the period 1971–2004? The paper starts by discussing whether research can answer this question at all and explains why a well-controlled study was not feasible. A case study approach was selected, and five major research projects were examined in detail for the purpose of trying to estimate their effects on road safety. Estimates of safety effects were developed for four of the projects, indicating that road safety measures that were at least to some extent based on the findings of the research projects have made major contributions to reducing the number of road accident fatalities in Sweden. The estimates are not analytically rigorous and should be treated as qualified guesses only. Causal inferences are not possible. Nevertheless, if taken at face value, they show that the benefits to society of road safety research are large and outweigh by a wide margin the costs of the research, and of the road safety measures developed as a result of research. Thus, even if the estimated safety benefits exaggerate the true effects, the benefits of applied road safety research are likely to be greater than the costs of conducting this research and implementing road safety measures developed by research. }
}
@article{Johansson2009809,
title = {A new method for assessing the risk of accident associated with darkness },
journal = {Accident Analysis & Prevention },
volume = {41},
number = {4},
pages = {809 - 815},
year = {2009},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2009.04.003},
url = {http://www.sciencedirect.com/science/article/pii/S0001457509000803},
author = {Östen Johansson and Per Ole Wanvik and Rune Elvik},
keywords = {Darkness},
keywords = {Accident risk},
keywords = {Odds ratio estimate},
keywords = {Confounding factors },
abstract = {This paper presents a new method for assessing the risk of accidents associated with darkness. The method estimates the risk of accident associated with darkness in terms of an odds ratio, which is defined as follows: [(number of accidents in darkness in a given hour of the day)/(number of accidents in daylight in the same hour of the day)]/[(Number of accidents in a given comparison hour when the case hour is dark)/(Number of accidents in a given comparison hour when the case hour is in daylight)]. This estimate of the risk of accident associated with darkness does not require data on exposure, but relies on the count of accidents in the same pair of hours throughout the year. One of the hours is dark part of the year, but has daylight the rest of the year. The comparison hour, which has daylight the whole year, is used to control for seasonal variations. The aim of relying on the same pair of hours throughout the year is to minimise the influence of potentially confounding factors. Estimates of the risk of injury accidents associated with darkness are developed on the basis of accident data for Norway, Sweden and the Netherlands. It is found that the risk of an injury accident increases by nearly 30% in darkness in urban areas, by nearly 50% in rural areas, and by about 40% for urban and rural areas combined (adjusted estimate). }
}
@article{Elvik2009876,
title = {An exploratory analysis of models for estimating the combined effects of road safety measures },
journal = {Accident Analysis & Prevention },
volume = {41},
number = {4},
pages = {876 - 880},
year = {2009},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2009.05.003},
url = {http://www.sciencedirect.com/science/article/pii/S0001457509001043},
author = {Rune Elvik},
keywords = {Road safety measures},
keywords = {Combined effects},
keywords = {Models for estimation},
keywords = {Exploratory analysis },
abstract = {Road safety programmes consisting of a large number of road safety measures have been developed in many countries. To estimate the effects of such programmes on the number of accidents, models for estimating the combined effects of road safety measures are needed. This paper presents an exploratory analysis of such models. There is very little empirical evidence to support model building. Based on a few studies that have evaluated the effects of multiple road safety measures introduced at the same locations, the paper compares two models. One of the models, the common residuals model, assumes that the (percentage) effect of a road safety measure remains unchanged when it is combined with other road safety measures. The other model, the dominant common residuals model, assumes that the most effective measure in a set of measures has a dominant effect that weakens the effects of other road safety measures it is combined with. Evidence from the few studies that were found is consistent with both these models. A study of the effects of a road safety programme implemented in Victoria, Australia between 1990 and 1996 indicated that the effects of safety measures are weakened when these measures are combined with other road safety measures. }
}
@article{Elvik2003557,
title = {How would setting policy priorities according to cost–benefit analyses affect the provision of road safety? },
journal = {Accident Analysis & Prevention },
volume = {35},
number = {4},
pages = {557 - 570},
year = {2003},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/S0001-4575(02)00034-9},
url = {http://www.sciencedirect.com/science/article/pii/S0001457502000349},
author = {Rune Elvik},
keywords = {Road safety},
keywords = {Policy},
keywords = {Efficiency},
keywords = {Cost–benefit analysis},
keywords = {Norway},
keywords = {Sweden },
abstract = {This paper analyses how setting priorities for road safety strictly according to cost–benefit analysis would affect the provision of road safety in Norway and Sweden. The paper is based on recent analyses of the efficiency of road safety policies in these two countries. The argument sometimes made by critics of cost–benefit analysis, that only a few road safety measures are cost-effective (have benefits greater than costs), is not supported. Cost-effective road safety policies could prevent between 50 and 60% of the current number of road accident fatalities in both Norway and Sweden, if pursued consistently during a period of 10 years (2002–2011). If current policies are continued, only about 10–15% of the current number of road accident fatalities are likely to be prevented during the next 10 years. A number of sources of inefficiency in road safety policy are identified. A source of inefficiency is anything that prevents policy priorities from being set according to cost–benefit analysis. These include: (a) lack of power, which means that national governments do not have the formal authority to introduce a certain road safety measure, in Europe, this applies to new vehicle safety standards, which are passed almost exclusively by the European Union; (b) the existence of social dilemmas, which means that measures that are cost-effective from a societal point of view are not so from the point of view of individual road users; (c) priority given to other policy objectives, in particular regional development. Scarcity of resources, which obtains when public budgets have to be increased to make room for all cost-effective measures, was not found to be a constraint. All cost-effective measures can be funded within current budgets, provided the use of inefficient measures ceases. }
}
@article{Elvik2002753,
title = {The effect on accidents of technical inspections of heavy vehicles in Norway },
journal = {Accident Analysis & Prevention },
volume = {34},
number = {6},
pages = {753 - 762},
year = {2002},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/S0001-4575(01)00075-6},
url = {http://www.sciencedirect.com/science/article/pii/S0001457501000756},
author = {Rune Elvik},
keywords = {Technical inspection},
keywords = {Heavy vehicles},
keywords = {Evaluation study},
keywords = {Multiple regression},
keywords = {Norway },
abstract = {This paper presents a study of the effects on accidents of technical inspections of heavy vehicles (trucks and buses) in Norway. Multiple regression analysis is applied in order to estimate the effects of technical inspections, controlling for annual trend in accident rate, the number of new drivers and annual economic growth. It is found that abolishing inspections may result in an increase of 5–10% in the number of heavy vehicles involved in injury accidents; increasing the number of inspections by 100% is associated with a similar reduction in the number of accidents. These results are not statistically significant and highly uncertain. The study clearly illustrates many of the difficulties often encountered in non-experimental accident research. }
}
@article{Amundsen2004115,
title = {Effects on road safety of new urban arterial roads },
journal = {Accident Analysis & Prevention },
volume = {36},
number = {1},
pages = {115 - 123},
year = {2004},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/S0001-4575(02)00133-1},
url = {http://www.sciencedirect.com/science/article/pii/S0001457502001331},
author = {Astrid H Amundsen and Rune Elvik},
keywords = {Arterial road},
keywords = {Urban area},
keywords = {Oslo},
keywords = {Safety effects},
keywords = {Evaluation },
abstract = {This paper presents an evaluation of the effects on road safety of new urban arterial roads in Oslo, Norway, and a synthesis of evidence from similar studies that have evaluated the safety effects of new urban arterial roads in other cities. A before-and-after study was made of four urban arterial road projects in Oslo. The study controlled for general accident trends in Oslo and for regression-to-the-mean. A statistically non-significant reduction of 9% in the number of injury accidents was found for all four projects combined. The effects on safety of new urban arterial roads were found to vary, depending on whether a new arterial road was built, or an existing arterial road upgraded by means of lane additions and reconstruction of junctions to interchanges. New arterial roads tend to induce more traffic, which tends to offset the benefits of a lower accident rate on the new roads. The results for other cities are very consistent with those for Oslo. For a total of seven cases in which new arterial roads were built, a statistically non-significant reduction of 1% in the number of injury accidents was found. Two cases that involved lane additions and converting at-grade junctions to interchanges resulted in a mean accident reduction of 51%, which was highly significant. On the average, the nine arterial road projects from which evidence was summarised resulted in a net induced traffic of 16%, and a net reduction in accident rate (accidents per million vehicle kilometres) of 18%. These effects almost cancel each other, leading to a very small net change in the expected number of accidents. }
}
@article{Elvik2006373,
title = {Road Safety by Design, H.M. Jagtman. Eburon Publishers, Delft (2004) },
journal = {Safety Science },
volume = {44},
number = {4},
pages = {373 - 374},
year = {2006},
note = {},
issn = {0925-7535},
doi = {http://dx.doi.org/10.1016/j.ssci.2005.09.007},
url = {http://www.sciencedirect.com/science/article/pii/S0925753505001001},
author = {Rune Elvik}
}
@article{Elvik2000147,
title = {Cost-benefit analysis of ambulance and rescue helicopters in Norway: What is the value of saving a human life? },
journal = {Air Medical Journal },
volume = {19},
number = {4},
pages = {147 - },
year = {2000},
note = {},
issn = {1067-991X},
doi = {http://dx.doi.org/10.1016/S1067-991X(00)90010-5},
url = {http://www.sciencedirect.com/science/article/pii/S1067991X00900105},
author = {Rune Elvik}
}
@article{Kim20053,
title = {A Tribute to Frank A. Haight: Founding Editor of Accident Analysis and Prevention },
journal = {Accident Analysis & Prevention },
volume = {37},
number = {1},
pages = {3 - },
year = {2005},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2004.10.008},
url = {http://www.sciencedirect.com/science/article/pii/S0001457504001046},
author = {Karl Kim and Rune Elvik}
}
@article{Kim2005389,
title = {New technology to better convey your mood (and research) },
journal = {Accident Analysis & Prevention },
volume = {37},
number = {3},
pages = {389 - 390},
year = {2005},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2005.01.001},
url = {http://www.sciencedirect.com/science/article/pii/S000145750500014X},
author = {Karl Kim and Rune Elvik}
}
@article{Elvik20019,
title = {Cost–benefit analysis of road safety measures: applicability and controversies },
journal = {Accident Analysis & Prevention },
volume = {33},
number = {1},
pages = {9 - 17},
year = {2001},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/S0001-4575(00)00010-5},
url = {http://www.sciencedirect.com/science/article/pii/S0001457500000105},
author = {Rune Elvik},
keywords = {Cost–benefit analysis},
keywords = {Road safety},
keywords = {Assessment of applicability },
abstract = {This paper discusses the applicability of cost–benefit analysis as an aid to policy making for road safety measures. A framework for assessing the applicability of cost–benefit analysis is developed. Five main types of criticism of cost–benefit analysis are identified:1. rejecting the basic principles of cost–benefit analysis as not applicable to road safety, 2. excluding some types of issues from the scope of calculation of costs and benefits, 3. setting policy objectives that are not amenable to cost–benefit analysis, 4. rejecting the need for maintaining a separation between policy objectives and policy programmes as required for cost–benefit analysis, and 5. rejecting, or denying the possibility of ever obtaining, acceptably valid and reliable economic valuations of the consequences of alternative policy programmes. It is concluded that rejecting the basic principles of cost–benefit analysis is a difficult position to defend, since these principles are simply a re-statement in economic terms of very general principles of rational choice. These principles are part of the normative basis of all formal techniques designed to aid policy making as well as the democratic system of government. Everybody, including those who advocate the use of cost–benefit analysis, agree that some issues are unsuitable for cost–benefit analysis, in particular those that involve basic human rights and fairness in distribution. There may, however, be disagreement with respect to the perception of a specific policy issue in terms of whether it is mainly about rights and fairness or mainly about the effective use of policy instruments to solve a social problem. Politicians may be tempted to set policy objectives that are ill suited for cost–benefit analysis, but this does not imply that cost–benefit analysis makes unreasonable assumptions. Perhaps the most important issue for the applicability of cost–benefit analysis is whether people in general have sufficiently well ordered preferences for economic valuations based on these preferences to make sense. }
}
@article{Elvik2006379,
title = {Are individual preferences always a legitimate basis for evaluating the costs and benefits of public policy?: The case of road traffic law enforcement },
journal = {Transport Policy },
volume = {13},
number = {5},
pages = {379 - 385},
year = {2006},
note = {},
issn = {0967-070X},
doi = {http://dx.doi.org/10.1016/j.tranpol.2006.01.002},
url = {http://www.sciencedirect.com/science/article/pii/S0967070X06000059},
author = {Rune Elvik},
keywords = {Crime},
keywords = {Offender},
keywords = {Benefits of crime},
keywords = {Enforcement},
keywords = {Road accidents},
keywords = {Moral legitimacy},
keywords = {Cost-benefit analysis },
abstract = {This paper discusses if it is appropriate to include the benefits that offenders get by violating the law in cost-benefit analyses of police enforcement, in the form of a loss of benefits from violations. The discussion is cast in the context of traffic law violations, a very common type of crime, which is usually not very strongly condemned from a moral point of view. Three options for cost-benefit analysis of traffic police enforcement are compared. The three options differ with respect to the treatment of (a) violator benefits from violations, and (b) outlays for traffic tickets given to violators. The implications of the choice of option are shown by means of four case illustrations, all referring to different types of traffic police enforcement in Norway. It is shown that every type of enforcement becomes less cost-effective when violator benefits are included in cost-benefit analyses. The legitimacy of including violator benefits as a benefit to society is discussed. It is concluded that, as far as traffic violations are concerned, benefits obtained by committing violations of the law cannot be treated as a legitimate societal benefit. }
}
@article{Elvik2002631,
title = {The importance of confounding in observational before-and-after studies of road safety measures },
journal = {Accident Analysis & Prevention },
volume = {34},
number = {5},
pages = {631 - 635},
year = {2002},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/S0001-4575(01)00062-8},
url = {http://www.sciencedirect.com/science/article/pii/S0001457501000628},
author = {Rune Elvik},
keywords = {Before-and-after study},
keywords = {Road safety measure},
keywords = {Confounding},
keywords = {Validity },
abstract = {This paper discusses the importance of confounding in observational before-and-after studies of road safety measures. The importance of the approach taken to controlling for confounding factors is shown by means of examples. It is shown that the size of the effect on accidents attributed to a road safety measure can be profoundly affected by which confounding factors are controlled for in an evaluation study, and the way this is done. Simple before-and-after studies, not controlling for any confounding factors should never be trusted and are likely to overstate the effects of road safety measures. }
}
@article{Elvik2003741,
title = {Assessing the validity of road safety evaluation studies by analysing causal chains },
journal = {Accident Analysis & Prevention },
volume = {35},
number = {5},
pages = {741 - 748},
year = {2003},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/S0001-4575(02)00077-5},
url = {http://www.sciencedirect.com/science/article/pii/S0001457502000775},
author = {Rune Elvik},
keywords = {Road safety},
keywords = {Evaluation},
keywords = {Causal chain},
keywords = {Validity},
keywords = {Assessment },
abstract = {This paper discusses how the validity of road safety evaluation studies can be assessed by analysing causal chains. A causal chain denotes the path through which a road safety measure influences the number of accidents. Two cases are examined. One involves chemical de-icing of roads (salting). The intended causal chain of this measure is: spread of salt → removal of snow and ice from the road surface → improved friction → shorter stopping distance → fewer accidents. A Norwegian study that evaluated the effects of salting on accident rate provides information that describes this causal chain. This information indicates that the study overestimated the effect of salting on accident rate, and suggests that this estimate is influenced by confounding variables the study did not control for. The other case involves a traffic club for children. The intended causal chain in this study was: join the club → improve knowledge → improve behaviour → reduce accident rate. In this case, results are rather messy, which suggests that the observed difference in accident rate between members and non-members of the traffic club is not primarily attributable to membership in the club. The two cases show that by analysing causal chains, one may uncover confounding factors that were not adequately controlled in a study. Lack of control for confounding factors remains the most serious threat to the validity of road safety evaluation studies. }
}
@article{Elvik2004841,
title = {To what extent can theory account for the findings of road safety evaluation studies? },
journal = {Accident Analysis & Prevention },
volume = {36},
number = {5},
pages = {841 - 849},
year = {2004},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2003.08.003},
url = {http://www.sciencedirect.com/science/article/pii/S0001457503001234},
author = {Rune Elvik},
keywords = {Road safety},
keywords = {Evaluation study},
keywords = {Theory},
keywords = {Explanation},
keywords = {Engineering effect},
keywords = {Behavioural effect},
keywords = {Checklists },
abstract = {This paper proposes a conceptual framework that can be used to assess to what extent the findings of road safety evaluation research make sense from a theoretical point of view. The effects of road safety measures are modelled as passing through two causal chains. One of these, termed the engineering effect, refers to the intended effects of a road safety measure on a set of risk factors related to accident occurrence or injury severity. The engineering effect of road safety measures is modelled in terms of nine basic risk factors, one or more of which any road safety measure needs to influence in order to have the intended effect on accidents or injuries. The other causal chain producing the effects of road safety measures is termed the behavioural effect, and refers to road user behavioural adaptations to road safety measures. The behavioural effect is related to the engineering effect, in the sense that certain properties of the engineering effect of a road safety measure influence the likelihood that behavioural adaptation will occur. The behavioural effect of a road safety measure is modelled in terms of six factors that influence the likelihood that behavioural adaptation will occur. The nine basic risk factors representing the engineering effect of a road safety measure, and the six factors influencing the likelihood of behavioural adaptation can be used as checklists in assessing whether or not the findings of road safety evaluation studies make sense from a theoretical point of view. At the current state of knowledge, a more stringent evaluation of the extent to which theory can explain the findings of road safety evaluation studies is, in most cases, not possible. }
}
@article{Elvik2000849,
title = {How much do road accidents cost the national economy? },
journal = {Accident Analysis & Prevention },
volume = {32},
number = {6},
pages = {849 - 851},
year = {2000},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/S0001-4575(00)00015-4},
url = {http://www.sciencedirect.com/science/article/pii/S0001457500000154},
author = {Rune Elvik},
keywords = {Road accidents},
keywords = {Costs},
keywords = {Gross national product },
abstract = {This paper presents estimates of how much road accidents cost the national economy, stated as a percentage of the gross national product (GNP). Official estimates of road accident costs from 1990 or later were compiled from easily accessible sources for twelve countries. Estimates of the gross national product were taken from \{OECD\} publications. On the average, the total costs of road accidents, including an economic valuation of lost quality of life, were estimated to about 2.5% of the gross national product. Excluding the valuation of lost quality of life, road accident costs on the average amounted to 1.3% of the gross national product. When valuation of lost quality of life is included, costs ranged from 0.5 to 5.7% of GNP. When valuation of lost quality of life is disregarded, costs ranged from 0.3 to 2.8% of GNP. }
}
@article{Elvik200037,
title = {Which are the relevant costs and benefits of road safety measures designed for pedestrians and cyclists? },
journal = {Accident Analysis & Prevention },
volume = {32},
number = {1},
pages = {37 - 45},
year = {2000},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/S0001-4575(99)00046-9},
url = {http://www.sciencedirect.com/science/article/pii/S0001457599000469},
author = {Rune Elvik},
keywords = {Impact assessment},
keywords = {Cost-benefit analysis},
keywords = {Pedestrian},
keywords = {Cyclist},
keywords = {State-of-the-art review },
abstract = {This paper discusses the current state-of-the-art with respect to impact assessment and cost-benefit analysis of measures designed to improve safety or mobility for pedestrians and cyclists. The study concludes that a number of impacts that are likely to regarded as important for pedestrians and cyclists are not included in current impact assessments and cost-benefit analyses as these are made in Norway. Impacts that are not currently included in impact assessments and cost-benefit analyses are: (a) changes in the amount of walking and cycling; (b) changes in travel time for pedestrians and cyclists; (c) changes in road user insecurity (feeling of safety); and (d) changes in road user health state. In order to include these effects in impact assessments and cost-benefit analyses, more needs to be known about their occurrence and monetary value. Hypothetical examples of ideally designed cost-benefit analyses are given, based on highly preliminary monetary values for travel time, insecurity and generalised costs of travel for pedestrians and cyclists. These analyses indicate that inclusion of these effects in cost-benefit analyses could make a major difference for the results of those analyses. }
}
@article{Elvik1999265,
title = {Can injury prevention efforts go too far?: Reflections on some possible implications of Vision Zero for road accident fatalities },
journal = {Accident Analysis & Prevention },
volume = {31},
number = {3},
pages = {265 - 286},
year = {1999},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/S0001-4575(98)00079-7},
url = {http://www.sciencedirect.com/science/article/pii/S0001457598000797},
author = {Rune Elvik},
keywords = {Vision Zero},
keywords = {Traffic deaths},
keywords = {Survival lottery},
keywords = {Mortality},
keywords = {Moral dilemma },
abstract = {The Swedish National Road Administration has launched a long term vision of a road transport system in which nobody is killed or sustains an injury resulting in permanent impairment (Vision Zero). This paper examines some possible implications of Vision Zero for traffic fatalities. The main points of the paper can be summarised as follows: An objective of eliminating traffic deaths can be interpreted as an application of a general principle of minimising mortality. Minimising overall mortality implies that a survival lottery must be introduced, at any rate as long as there is a shortage of organs for transplants. A survival lottery is a scheme in which people are drawn at random to sacrifice their life for the benefit of others. An objective of eliminating a certain cause of death, like traffic accidents, may be so expensive to realise that there is so much less resources available to control other causes of death that general mortality increases. Several analyses of the relationship between income per capita and general mortality based on Norwegian data document a negative relationship between income and mortality. The loss of income that induces an additional statistical death, due to economic inefficiency, is estimated to between 25 and 317 million \{NOK\} (3.8–47.5 million \{US\} dollars). These estimates are in line with those of most previous studies. No study of the relationship between income and mortality fully satisfies commonly used criteria of causality. However, the balance of evidence suggests that the relationship between income and mortality is a causal one. A hypothetical programme designed to implement Vision Zero for traffic fatalities was developed and its effects on the number of fatalities estimated. Implementing the whole programme could reduce the number of traffic deaths in Norway from about 300 per year to about 90 per year. Applying the lowest estimate of the income loss that induces an additional death (25 million NOK), it was estimated that implementing the entire hypothetical Vision Zero programme would increase general mortality by about 1355. This would lead to a net increase of about 1145 deaths per year (1355 minus 210 prevented traffic deaths). The analyses presented in this paper show that the possibility cannot be ruled out that a massive effort to eliminate traffic deaths would be counterproductive in terms of overall mortality. This possibility must be regarded as a moral dilemma by advocates of Vision Zero, who have invoked the ethical principle that ‘one must always do everything in one’s power to prevent death or serious injury’ to justify the vision. }
}
@article{Elvik2006742,
title = {Laws of accident causation },
journal = {Accident Analysis & Prevention },
volume = {38},
number = {4},
pages = {742 - 747},
year = {2006},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2006.01.005},
url = {http://www.sciencedirect.com/science/article/pii/S0001457506000145},
author = {Rune Elvik},
keywords = {Accident},
keywords = {Causation},
keywords = {Scientific law},
keywords = {Explanation},
keywords = {Empirical testing },
abstract = {This paper suggests that the influence of a number of important risk factors on road accidents can be described in terms of a few highly general statistical regularities that determine the shape of the relationship between the risk factors and accident occurrence. The statistical regularities are referred to as “laws of accident causation”. The following “laws” are proposed:1. The universal law of learning, which states that the ability to detect and control traffic hazards increases uniformly as the amount of travel increases. This law implies that accident rate per unit of exposure will decline as the amount of exposure increases. 2. The law of rare events, which states that the more rarely a certain risk factor is encountered the larger is its effect on accident rate. This law implies that a risk factor encountered on, for example 5% of all trips, will be associated with a greater increase in accident rate than an otherwise identical risk factor encountered on 50% of all trips. 3. The law of complexity, which states that the more units of information per unit of time a road user must attend to, the higher becomes the probability that an error will made. This law implies that accident rate will increase the more elements of information the traffic environment contains. 4. The law of cognitive capacity, which states that the more cognitive capacity approaches its limits, the higher the accident rate. This law implies that impairments affecting mental functions will have a greater effect on accident rate than impairments affecting physical functioning only. Instances of all these laws, as well as a discussion of to how the laws can be tested empirically, are given. It is hoped that proposing a few basic mechanisms that can summarise the impact of a number of risk factors will stimulate research that may lead to a more general theory of accident causation. }
}
@article{Elvik2006678,
title = {Economic deregulation and transport safety: A synthesis of evidence from evaluation studies },
journal = {Accident Analysis & Prevention },
volume = {38},
number = {4},
pages = {678 - 686},
year = {2006},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2005.12.013},
url = {http://www.sciencedirect.com/science/article/pii/S0001457505002150},
author = {Rune Elvik},
keywords = {Deregulation},
keywords = {Transport safety},
keywords = {Evaluation},
keywords = {Meta-analysis },
abstract = {This paper presents a synthesis of evidence from studies that have evaluated the impacts of economic deregulation on transport safety. Most of these studies refer to aviation or road transport. Very few studies deal with deregulation of rail transport. There are no studies of maritime transport, which has never been regulated the same way as other modes of transport. The review includes studies that have attempted to quantify the impacts of transport deregulation on transport safety. Each study contains one or more estimates of the effect on transport safety of deregulation. Summary estimates of effect have been derived from the individual estimates of effect by means of meta-analysis. Airline deregulation, which has only been evaluated in the United States, does not appear to influence the safety of air travel. Deregulation of road transport has been evaluated in several countries. The summary estimate of effect indicates that no statistically significant changes in road safety have occurred as a result of deregulation. Deregulation of rail transport has only been evaluated in Great Britain and the United States. The experience so far suggests that deregulation of railways is associated with improved rail safety. This association does, however, not necessarily imply a causal relationship. }
}
@article{Elvik2005515,
title = {Road safety effects of porous asphalt: a systematic review of evaluation studies },
journal = {Accident Analysis & Prevention },
volume = {37},
number = {3},
pages = {515 - 522},
year = {2005},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2005.01.003},
url = {http://www.sciencedirect.com/science/article/pii/S0001457505000175},
author = {Rune Elvik and Poul Greibe},
keywords = {Road safety},
keywords = {Evaluation study},
keywords = {Porous asphalt},
keywords = {Meta-analysis},
keywords = {Risk factors },
abstract = {This paper presents a systematic review of studies that have evaluated the effects on road safety of porous asphalt. Porous asphalt is widely used on motorways in Europe, mainly in order to reduce traffic noise and increase road capacity. A meta-analysis was made of six studies, containing a total of eighteen estimates of the effect of porous asphalt on accident rates. No clear effect on road safety of porous asphalt was found. All summary estimates of effect indicated very small changes in accident rates and very few were statistically significant at conventional levels. Studies that have evaluated the effects of porous asphalt on nine different risk factors associated with accident occurrence were also reviewed. It was found that four of the risk factors were favourably influenced by porous asphalt, three were adversely influenced, and two were not influenced by porous asphalt. The net impact of these changes in risk factors on accident occurrence cannot be predicted. On the whole, the research that has been reported so far regarding road safety effects of porous asphalt is inconclusive. The studies are not of high quality and the findings are inconsistent. }
}
@article{Elvik20051005,
title = {How accurately does the public perceive differences in transport risks?: An exploratory analysis of scales representing perceived risk },
journal = {Accident Analysis & Prevention },
volume = {37},
number = {6},
pages = {1005 - 1011},
year = {2005},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2005.05.003},
url = {http://www.sciencedirect.com/science/article/pii/S0001457505000825},
author = {Rune Elvik and Torkel Bjørnskau},
keywords = {Risk perception},
keywords = {Transport risks},
keywords = {Statistical estimates of risk},
keywords = {Correlation },
abstract = {This paper probes the extent to which the public accurately perceives differences in transport risks. The paper is based on a survey of a random sample of the Norwegian population, conducted in September 2003. In the survey, respondents were asked: “How safe do you think it is to travel by means of (bus, train, etc.)?” Answers were given as: very safe, safe, a little unsafe, and very unsafe. A cursory examination of the answers suggested that the Norwegian public was quite well informed about differences in the risk of accident between different modes of transport, as well as between groups formed according to age and gender for each mode of transport. This paper probes the relationship between statistical estimates of risk and summary representations of perceived risk more systematically. It is found that the differences in fatality rate between different modes of transport are quite well perceived by the Norwegian public, irrespective of the way in which perceived risk is represented numerically. The relationship between statistical estimates of risk and numerical representations of perceived risk for each mode of transport is more sensitive to the choice of a numerical representation of perceived risk. A scale in which the answer “very safe” is assigned the value of 0.01 and the answer “very unsafe” is assigned the value of 10 is found to perform quite well. When the perception of risk is represented numerically according to this scale, a positive correlation between statistically estimated risk and perceived risk is found in seven of the eight comparisons that were made to determine how well variation in accident rates according to age and gender for car occupants, car drivers, cyclists and pedestrians are perceived. }
}
@article{Elvik2001327,
title = {Area-wide urban traffic calming schemes: a meta-analysis of safety effects },
journal = {Accident Analysis & Prevention },
volume = {33},
number = {3},
pages = {327 - 336},
year = {2001},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/S0001-4575(00)00046-4},
url = {http://www.sciencedirect.com/science/article/pii/S0001457500000464},
author = {Rune Elvik},
keywords = {Traffic calming},
keywords = {Road safety},
keywords = {Evaluation studies},
keywords = {Meta-analysis },
abstract = {This paper presents a meta-analysis of 33 studies that have evaluated the effects on road safety of area-wide urban traffic calming schemes. Area-wide urban traffic calming schemes are typically implemented in residential areas in towns in order to reduce the environmental and safety problems caused by road traffic. A hierarchical road system is established and through traffic is removed from residential streets by means of, for example, street closures or one-way systems. Speed reducing devices are often installed in residential streets. Main roads are improved in order to carry a larger traffic volume without additional delays or more accidents. The meta-analysis shows that area-wide urban traffic calming schemes on the average reduce the number of injury accidents by about 15%. The largest reduction in the number of accidents is found for residential streets (about 25%), a somewhat smaller reduction is found for main roads (about 10%). Similar reductions are found in the number of property damage only accidents. The results of evaluation studies are robust with respect to study design. There is no evidence of publication bias in evaluation studies. Study findings are found to have high external validity. }
}
@article{Christensen200747,
title = {Effects on accidents of periodic motor vehicle inspection in Norway },
journal = {Accident Analysis & Prevention },
volume = {39},
number = {1},
pages = {47 - 52},
year = {2007},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2006.06.003},
url = {http://www.sciencedirect.com/science/article/pii/S0001457506001060},
author = {Peter Christensen and Rune Elvik},
keywords = {Evaluation},
keywords = {Negative binomial regression},
keywords = {Periodic motor vehicle inspection },
abstract = {An extensive programme of periodic motor vehicle inspection was introduced in Norway after 1995, when the treaty between Norway and the European Union (EU) granting Norway (not a member of the EU) access to the \{EU\} inner market took effect (The \{EEA\} treaty). This paper evaluates the effects on accidents of periodic inspections of cars. Trucks and buses were not included in the study. Negative binomial regression models were fitted to data on accidents and inspections created by merging data files provided by a major insurance company and by the Public Roads Administration. Technical defects prior to inspection were associated with an increased accident rate. Inspections were found to strongly reduce the number of technical defects in cars. Despite this, no effect of inspections on accident rate were found. This finding is inconsistent with the fact that technical defects appear to increase the accident rate; one would expect the repair of such defects to reduce the accident rate. Potential explanations of the findings in terms of behavioural adaptation among car owners are discussed. It is suggested that car owners adapt driving behaviour to the technical condition of the car and that the effect attributed to technical defects before inspection may in part be the result of a tendency for owners who are less concerned about safety to neglect the technical condition of their cars. These car owners might have had a higher accident rate than other car owners irrespective of the technical condition of the car. }
}
@article{Elvik1996339,
title = {Does prior knowledge of safety effect help to predict how effective a measure will be? },
journal = {Accident Analysis & Prevention },
volume = {28},
number = {3},
pages = {339 - 347},
year = {1996},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/0001-4575(95)00073-9},
url = {http://www.sciencedirect.com/science/article/pii/0001457595000739},
author = {Rune Elvik},
keywords = {Safety measure},
keywords = {Evaluation},
keywords = {Prediction},
keywords = {Meta-analysis},
keywords = {Testing },
abstract = {Studies evaluating the effects of traffic safety measures are often done for the purpose of predicting the effects of future applications of the measures. The predictive value of evaluation studies is unknown. Some general arguments for and against attributing a general predictive value to the results of evaluation studies are discussed. Predictability is shown to depend on many factors. Meta-analyses of evidence from evaluation studies can be used as a basis for testing the predictive performance of such studies. The predictive performance of studies that have evaluated the safety effects of road lighting and traffic separation is tested. Predictive performance is found to depend mainly on whether the results of evaluation studies are stable over time or exhibit a trend. In the latter case, predictions based on evidence accumulated before the trend became apparent can be very erroneous. It is shown that increasing the amount of evidence that predictions are based on does not necessarily make the predictions more accurate. More research does not always improve predictive performance. }
}
@article{Elvik19951385,
title = {The validity of using health state indexes in measuring the consequences of traffic injury for public health },
journal = {Social Science & Medicine },
volume = {40},
number = {10},
pages = {1385 - 1398},
year = {1995},
note = {},
issn = {0277-9536},
doi = {http://dx.doi.org/10.1016/0277-9536(94)00264-T},
url = {http://www.sciencedirect.com/science/article/pii/027795369400264T},
author = {Rune Elvik},
keywords = {\{QALY\}},
keywords = {health state index},
keywords = {traffic injury},
keywords = {validity},
keywords = {public health },
abstract = {This paper describes an assessment of the validity of using health state indexes as a means of describing the consequences of traffic injury for public health. Three issues are discussed: (1) Can questionnaire data be used as input for estimating health state values by means of health state indexes? (2) Can the validity of describing the consequences of traffic injury by means of different health state indexes (QALY-indexes) be assessed? (3) Can estimated health state values be used directly as a basis for decision making? It is concluded that questionnaire data can be used as input for health state value estimation. Four health state indexes are compared: The Quality of Well Being Scale, The McMaster Health Classification System, The Rosser and Kind Index and The EuroQol Instrument (transformed version). It is concluded that an assessment of the validity of these indexes is possible, and that the EuroQol Instrument appears to be the most valid of the four indexes that are compared. None of the four indexes give values that are consistent with public policy objectives, but objectives were not set with the benefit of knowing the relative utility loss associated with injuries at different levels of severity. }
}
@article{Elvik1998255,
title = {Evaluating the statistical conclusion validity of weighted mean results in meta-analysis by analysing funnel graph diagrams },
journal = {Accident Analysis & Prevention },
volume = {30},
number = {2},
pages = {255 - 266},
year = {1998},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/S0001-4575(97)00076-6},
url = {http://www.sciencedirect.com/science/article/pii/S0001457597000766},
author = {Rune Elvik},
keywords = {Meta-analysis},
keywords = {Weighted mean},
keywords = {Funnel graph},
keywords = {Validity},
keywords = {Evaluation study },
abstract = {The validity of weighted mean results estimated in meta-analysis has been criticized. This paper presents a set of simple statistical and graphical techniques that can be used in meta-analysis to evaluate common points of criticism. The graphical techniques are based on funnel graph diagrams. Problems and techniques for dealing with them that are discussed include: 1. (1) the so-called ‘apples and oranges’ problem, stating that mean results in meta-analysis tend to gloss over important differences that should be highlighted. A test of the homogeneity of results is described for testing the presence of this problem. If results are highly heterogeneous, a random effects model of meta-analysis is more appropriate than the fixed effects model of analysis. 2. (2) The possible presence of skewness in a sample of results. This can be tested by comparing the mode, median and mean of the results in the sample. 3. (3) The possible presence of more than one mode in a sample of results. This can be tested by forming a frequency distribution of the results and examining the shape of this distribution. 4. (4) The sensitivity of the mean to the possible presence of atypical results (outliers) can be tested by comparing the overall mean to the mean of all results except the one suspected of being atypical. 5. (5) The possible presence of publication bias can be tested by visual inspection of funnel graph diagrams in which data points have been sorted according to statistical significance and direction of effect. 6. (6) The possibility of underestimating the standard error of the mean in meta-analyses by using multiple, correlated results from the same study as the unit of analysis can be addressed by using the jack-knife technique for estimating the uncertainty of the mean. Brief examples, taken from road safety research, are given of all these techniques. }
}
@article{Elvik1998101,
title = {Are road safety evaluation studies published in peer reviewed journals more valid than similar studies not published in peer reviewed journals? },
journal = {Accident Analysis & Prevention },
volume = {30},
number = {1},
pages = {101 - 118},
year = {1998},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/S0001-4575(97)00068-7},
url = {http://www.sciencedirect.com/science/article/pii/S0001457597000687},
author = {Rune Elvik},
keywords = {Road safety},
keywords = {Evaluation study},
keywords = {Study validity},
keywords = {Peer review},
keywords = {Scientific journal },
abstract = {The peer review system of scientific journals is commonly assumed to prevent seriously flawed research from getting published. This paper compares the quality of 44 road safety evaluation studies published in peer reviewed journals to the quality of 79 evalutation studies dealing with the same safety measures, but not published in peer reviewed journals, in terms of seven criteria of study validity. Studies were scored for validity in terms of 1. (1) sampling technique, 2. (2) total sample size, 3. (3) mean sample size for each result, 4. (4)specification of accident or injury severity, 5. (5) study design, 6. (6) number of confounding factors controlled and 7. (7) number of moderator variables specified. Confounding factors are all factors that distrurb the attribution of a causal relationship between the safety measure being evalutated and the observed changes in safety, moderator variables are all variables that influence the size of the effect of the safety measure. Very few statistically reliable differences in study validity were found between studies published in peer reviewed journals and studies not published in such journals. There was, at best, a weak tendency for studies published in peer reviewed journals to score higher for validity. An interaction was found between author affiliation and type of publication with respect to study validity. Studies published in peer reviewed journals by authors who were at a university scored highest for validity. For a number of reasons, this study must be regarded as exploratory and its results as indicative only. The study does, however, point to a line of research that might be worth pursuing in larger and more rigorous studies. }
}
@article{Elvik1993383,
title = {The effects on accidents of compulsory use of daytime running lights for cars in Norway },
journal = {Accident Analysis & Prevention },
volume = {25},
number = {4},
pages = {383 - 398},
year = {1993},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/0001-4575(93)90068-8},
url = {http://www.sciencedirect.com/science/article/pii/0001457593900688},
author = {Rune Elvik},
abstract = {The use of daytime running lights was made mandatory for new cars in Nroway in 1985 and for all cars in 1988. This paper examines the effectiveness of this regulation as an accident countermeasure. The paper relies on the same study design and method of analysis as previous studies of similar laws in Finland and Sweden. Four hypotheses concerning the effects of daytime running lights are tested. None of them was supported. The total number of multiparty accidents in daylight was not reduced. Pedestrian accidents and accidents in twilight were not reduced. The number of rear-end collisions increased by about 20%. Daytime running lights appear to reduce daytime multiparty accidents only during summer (by about 15%) and only for multivehicle accidents, excluding rear-end collisions. The possibility that confounding factors may have influenced study results is examined. It is concluded that such an influence cannot be ruled out. The discussion of the results highlights the difficulties of reaching clear and defensible conclusions in nonexperimental accident research of the kind reported in this paper. }
}
@article{Elvik1994719,
title = {The external costs of traffic injury: Definition, estimation, and possibilities for internalization },
journal = {Accident Analysis & Prevention },
volume = {26},
number = {6},
pages = {719 - 732},
year = {1994},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/0001-4575(94)90050-7},
url = {http://www.sciencedirect.com/science/article/pii/0001457594900507},
author = {Rune Elvik},
abstract = {The external costs of traffic injury in Norway are estimated. External costs are all costs that are imposed on others and not borne by the person whose activity generates the costs. Three types of external cost are identified: system externalities, physical injury externalities, and traffic volume externalities. System externalities are costs that road users impose on the rest of society. Physical injury externalities are costs that one group of road users imposes upon another in crashes in which both groups are involved. Traffic volume externalities are the costs imposed on other road users when an additional road user joins traffic. System externalities are estimated to be about 30% of the total cost of traffic injury. Physical injury externalities are estimated to be about 10% of the total cost of traffic injury. No precise estimate can be given for traffic volume externalities. Possibilities for internalizing the external costs are discussed. In Norway, current taxes on ownership and use of motor vehicles cover the external costs of traffic injury, although the taxes were not designed with this purpose in mind. }
}
@article{Bjørnskau1992507,
title = {Can road traffic law enforcement permanently reduce the number of accidents? },
journal = {Accident Analysis & Prevention },
volume = {24},
number = {5},
pages = {507 - 520},
year = {1992},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/0001-4575(92)90059-R},
url = {http://www.sciencedirect.com/science/article/pii/000145759290059R},
author = {Torkel Bjørnskau and Rune Elvik},
abstract = {In this paper it is argued that conventional analyses of road user adaptation to traffic law enforcement, based on parametric rational-choice theory, are flawed. Such analyses only consider road-user actions as a response to enforcement level and penalty size and do not simultaneously consider enforcement as a response to road-user behaviour. If each party is considered a rational agent who adapts to the other's behaviour, the proper way to analyze the outcomes is by the way of game theory. A game-theoretic model is presented and the main implications are: (i) most attempts at enforcing road traffic legislation will not have any lasting effects, either on road-user behaviour or on accidents; (ii) imposing stricter penalties (in the form of higher fines or longer prison sentences) will not affect road-user behaviour; (iii) imposing stricter penalties will reduce the level of enforcement; (iv) implementing automatic traffic surveilance techniques and/or allocating enforcement resources according to a chance mechanism, and not according to police estimates of violation probability, can make enforcement effects last, but both alternatives are difficult to implement. Relevant empirical studies are reviewed, and they seem to support the conclusions arrived at by the game-theoretic model. }
}
@article{Elvik1995523,
title = {The safety value of guardrails and crash cushions: A meta-analysis of evidence from evaluation studies },
journal = {Accident Analysis & Prevention },
volume = {27},
number = {4},
pages = {523 - 549},
year = {1995},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/0001-4575(95)00003-I},
url = {http://www.sciencedirect.com/science/article/pii/000145759500003I},
author = {Rune Elvik},
keywords = {Guardrail},
keywords = {Meta-analysis},
keywords = {Evaluation studies},
keywords = {Safety effectiveness },
abstract = {Evidence from 32 studies that have evaluated the safety effects of median barriers, guardrails along the edge of the road, and crash cushions (impact attenuators) is summarized by means of a metaanalysis. Two hundred and thirty-two (232) estimates of safety effects are included in the meta-analysis. The presence of publication bias is tested by means of the funnel graph method. For most subsets of the data, no evidence of publication bias is found. Weighted mean estimates of safety effects are computed by means of the logodds method. Median barriers are found to increase accident rate, but reduce accident severity. Guardrails and crash cushions are found to reduce both accident rate and accident severity. The effects of guardrails and crash cushions on accident rate have been less extensively studied than the effects on accident severity. Current estimates of the effects on accident rate are highly uncertain because of methodological shortcomings of available studies. The effects of guardrails on accident severity are found to be quite robust with respect to study design and the number of confounding variables controlled in each study. In general, random variation in the number of accidents is the most important source of variation in study results. }
}
@article{Elvik1997191,
title = {Evaluations of road accident blackspot treatment: A case of the iron law of evaluation studies? },
journal = {Accident Analysis & Prevention },
volume = {29},
number = {2},
pages = {191 - 199},
year = {1997},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/S0001-4575(96)00070-X},
url = {http://www.sciencedirect.com/science/article/pii/S000145759600070X},
author = {Rune Elvik},
keywords = {Road accident},
keywords = {Blackspot},
keywords = {Treatment},
keywords = {Evaluation study},
keywords = {Meta-analysis },
abstract = {Numerous evaluation studies have reported large accident reductions when road accident blackspots are treated. A critical examination of these studies reveals that many of them do not account for the effects of well known confounding factors, like the regression-to-the-mean effect that is likely to occur at road accident blackspots. This paper shows that the more confounding factors evaluation studies account for, the smaller becomes the accident reduction attributed to blackspot treatment. Studies that account for both regression-to-the-mean and a possible accident migration to neighbouring untreated sites do not show any net accident reduction at all. This tendency conforms to the so called Iron Law of evaluation studies, which states that the more confounding factors an evaluation study accounts for, the less likely it is to show beneficial effects of the programme evaluated. Possible explanations of accident migration are discussed in the paper. }
}
@article{Elvik1993569,
title = {Quantified road safety targets: A useful tool for policy making? },
journal = {Accident Analysis & Prevention },
volume = {25},
number = {5},
pages = {569 - 583},
year = {1993},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/0001-4575(93)90009-L},
url = {http://www.sciencedirect.com/science/article/pii/000145759390009L},
author = {Rune Elvik},
abstract = {The safety performance of Norwegian counties where quantified road safety targets were set is compared to the safety performance of counties where only qualitative road safety targets were set. Quantified targets are classified according to their ambitiousness. Safety performance is compared for two four-year road planning terms: 1982–1985 and 1986–1989. The study shows that counties where quantified safety targets were set succeeded in reducing the accident rate per kilometre of travel more than counties relying on qualitative targets only. The best performance was achieved by counties with highly ambitious quantified targets. Safety performance was related both to targets and to the level of spending on road safety programmes. Improving safety did not lead to reduced mobility, with the exception of lowered speed limits on less than 10% of the road system. The possibility that confounding factors generated these results is discussed. It is concluded that none of the confounding factors included in the study exerted a major influence. A number of potentially confounding factors could not be included, due to lack of data. The chief policy implication of the study is that setting ambitious quantified road safety targets can help policy making by making it easier to implement effective countermeasures and set priorities effectively. }
}
@article{Elvik1996685,
title = {A meta-analysis of studies concerning the safety effects of daytime running lights on cars },
journal = {Accident Analysis & Prevention },
volume = {28},
number = {6},
pages = {685 - 694},
year = {1996},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/S0001-4575(96)00041-3},
url = {http://www.sciencedirect.com/science/article/pii/S0001457596000413},
author = {Rune Elvik},
keywords = {Daytime running lights},
keywords = {Evaluation studies},
keywords = {Meta-analysis},
keywords = {Safety effects },
abstract = {A meta-analysis of 17 studies that have evaluated the effects on traffic safety of using daytime running lights (DRL) on cars is presented. A distinction is made between studies that have evaluated the effects of \{DRL\} on the accident rates of each car using it and studies that have evaluated changes in the total number of accidents in a country following the introduction of mandatory use of DRL. Three different definitions of the measure of safety effects are compared and their validity discussed. It is concluded that the use of \{DRL\} on cars reduces the number of multi-party daytime accidents by about 10–15% for cars using DRL. The estimated effects on the total number of accidents of introducing \{DRL\} laws are somewhat smaller, 3–12% reduction in multi-party daytime accidents, and are likely to contain uncontrolled confounding effects. There is no evidence to indicate that \{DRL\} affects types of accident other than multi-party daytime accidents. }
}
@article{Elvik1995237,
title = {An analysis of official economic valuations of traffic accident fatalities in 20 motorized countries },
journal = {Accident Analysis & Prevention },
volume = {27},
number = {2},
pages = {237 - 247},
year = {1995},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/0001-4575(94)00060-Y},
url = {http://www.sciencedirect.com/science/article/pii/000145759400060Y},
author = {Rune Elvik},
keywords = {Traffic accident},
keywords = {Cost},
keywords = {Fatality},
keywords = {Motorized country },
abstract = {Official economic valuations (costs) of a traffic accident fatality in 20 motorized countries are described. The economic valuation per fatality varies from 0.87 million Norwegian kroner to 17.80 million kroner. The mean value is 5.69 million kroner. An attempt is made to explain the differences in official cost estimates. The valuation method used in estimating the costs has major importance for the level of costs. Recently, a number of motorized countries have accepted the willingness-to-pay approach as the basis for the economic valuation of traffic accident fatalities. In these countries, this has led to major upward revisions of previous cost estimates. }
}
@article{Elvik1988261,
title = {Some difficulties in defining populations of “entities” for estimating the expected number of accidents },
journal = {Accident Analysis & Prevention },
volume = {20},
number = {4},
pages = {261 - 275},
year = {1988},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/0001-4575(88)90054-1},
url = {http://www.sciencedirect.com/science/article/pii/0001457588900541},
author = {Rune Elvik},
abstract = {In order to estimate the expected number of accidents for an “entity” (intersection, road section, driver), the entity must be assigned membership in some population of similar entities. Concepts like “bias-by-selection” have no meaning unless they refer to selection from some population. In this article, three problems in defining such populations, with particular reference to populations of road sections, are discussed. The problems are: (1) how to define an adequate “reference” population for various road safety measures; (2) problems created by the “moving” definition of road sections with an abnormal accident count; and (3) problems in treating road sections of different length as members of the same population of sections. It is concluded that only entities which are “similar” in some respect may constitute a population. There is no satisfactory way of defining a population of moving road sections. Likewise, the problem of whether, e.g., a four-kilometer section should be seen as a sample of one unit from a population of four-kilometer sections, or as a sample of, e.g., four units from a population of one-kilometer sections is at present unsolved. A theory must be built in order to solve these difficulties of defining populations, in particular populations of road sections. }
}
@article{Elvik1999125,
title = {The effects on accidents of studded tires and laws banning their use: a meta-analysis of evaluation studies },
journal = {Accident Analysis & Prevention },
volume = {31},
number = {1–2},
pages = {125 - 134},
year = {1999},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/S0001-4575(98)00054-2},
url = {http://www.sciencedirect.com/science/article/pii/S0001457598000542},
author = {Rune Elvik},
keywords = {Studded tires},
keywords = {Road safety},
keywords = {Evaluation study},
keywords = {Meta-analysis },
abstract = {Studies that have evaluated the effects on accidents of studded tires are reviewed. There are two types of evaluation studies with respect to the safety effects of studded tires: (1) Studies of the effect on automobile accident rates of using studded tires; and (2) studies of the effect on accidents of banning the use of studded tires. The results of studies of the effects of studded tires on automobile accident rates are found to vary substantially, depending on the quality of the study design. Recent studies employing multivariate techniques of analysis to control for confounding factors, attribute to studded tires minor declines in automobile accident rates of 5% for snow- or ice-covered roads, 2% for bare roads and 4% for all road surfaces combined. The results of these studies are consistent with the most recent estimates of the effect on accidents of banning studded tires. It is concluded that studded tires probably confer a slight safety benefit during wintertime. }
}
@comment{{Matthew G. Karlaftis PAPERS}}
@article{Iliopoulou201566,
title = {Route planning for a seaplane service: The case of the Greek Islands },
journal = {Computers & Operations Research },
volume = {59},
number = {0},
pages = {66 - 77},
year = {2015},
note = {},
issn = {0305-0548},
doi = {http://dx.doi.org/10.1016/j.cor.2015.01.004},
url = {http://www.sciencedirect.com/science/article/pii/S0305054815000118},
author = {Christina Iliopoulou and Konstantinos Kepaptsoglou and Matthew G. Karlaftis},
keywords = {Seaplanes},
keywords = {Routing},
keywords = {Genetic algorithms },
abstract = {Abstract Seaplanes offer a time and cost-efficient service for supporting transportation needs in island chains. This paper investigates the design of a seaplane network connecting the Greek islands with the mainland, a service currently accommodated by ferries. Design of seaplane routes is modeled as a multi-objective capacitated vehicle routing problem with simultaneous pickups and deliveries and route length deadlines. A genetic algorithm coupled with a hybrid process is used to solve the model. Results show that a network of 11 routes with maximum flight duration of 5 h can adequately cover estimated daily transportation needs between the Greek mainland and the islands. Further, realistic increases in seaplane capacity and/or cruising speed will have only a moderate impact on reducing the number of required routes. }
}
@article{Kepaptsoglou2015,
title = {Weather impact on containership routing in closed seas: A chance-constraint optimization approach },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {},
number = {0},
pages = { - },
year = {2015},
note = {},
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/j.trc.2015.01.027},
url = {http://www.sciencedirect.com/science/article/pii/S0968090X15000352},
author = {Konstantinos Kepaptsoglou and Grigorios Fountas and Matthew G. Karlaftis},
keywords = {Ship routing},
keywords = {Containerships},
keywords = {\{VRP\}},
keywords = {Stochastic travel times},
keywords = {Chance-constrained model},
keywords = {Pick-ups and deliveries},
keywords = {Time deadlines },
abstract = {Abstract Weather conditions have a strong effect on the operation of vessels and unavoidably influence total time at sea and associated transportation costs. The velocity and direction of the wind in particular may considerably affect travel speed of vessels and therefore the reliability of scheduled maritime services. This paper considers weather effects in containership routing; a stochastic model is developed for determining optimal routes for a homogeneous fleet performing pick-ups and deliveries of containers between a hub and several spoke ports, while incorporating travel time uncertainties attributed to the weather. The problem is originally formulated as a chance-constrained variant of the vehicle routing problem with simultaneous pick-ups and deliveries and time constraints and solved using a genetic algorithm. The model is implemented to a network of island ports of the Aegean Sea. Results on the application of algorithm reveal that a small fleet is sufficient enough to serve network’s islands, under the influence of minor delays. A sensitivity analysis based on alternative scenarios in the problem’s parameters, leads to encouraging conclusions with respect to the efficiency and robustness of the algorithm. }
}
@article{Vlahogianni20143,
title = {Short-term traffic forecasting: Where we are and where we’re going },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {43, Part 1},
number = {0},
pages = {3 - 19},
year = {2014},
note = {Special Issue on Short-term Traffic Flow Forecasting },
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/j.trc.2014.01.005},
url = {http://www.sciencedirect.com/science/article/pii/S0968090X14000096},
author = {Eleni I. Vlahogianni and Matthew G. Karlaftis and John C. Golias},
keywords = {Short-term traffic},
keywords = {Prediction models},
keywords = {Intelligent Transportation Systems},
keywords = {Responsive algorithms},
keywords = {Time series analysis},
keywords = {Computational intelligence },
abstract = {Abstract Since the early 1980s, short-term traffic forecasting has been an integral part of most Intelligent Transportation Systems (ITS) research and applications; most effort has gone into developing methodologies that can be used to model traffic characteristics and produce anticipated traffic conditions. Existing literature is voluminous, and has largely used single point data from motorways and has employed univariate mathematical models to predict traffic volumes or travel times. Recent developments in technology and the widespread use of powerful computers and mathematical models allow researchers an unprecedented opportunity to expand horizons and direct work in 10 challenging, yet relatively under researched, directions. It is these existing challenges that we review in this paper and offer suggestions for future work. }
}
@article{Spyropoulou201439,
title = {Intelligent Speed Adaptation and driving speed: Effects of different system \{HMI\} functionalities },
journal = {Transportation Research Part F: Traffic Psychology and Behaviour },
volume = {24},
number = {0},
pages = {39 - 49},
year = {2014},
note = {},
issn = {1369-8478},
doi = {http://dx.doi.org/10.1016/j.trf.2014.02.008},
url = {http://www.sciencedirect.com/science/article/pii/S1369847814000229},
author = {Ioanna K. Spyropoulou and Matthew G. Karlaftis and Nick Reed},
keywords = {Speed},
keywords = {Intelligent Speed Adaptation},
keywords = {Human machine interface},
keywords = {Simulator},
keywords = {Intelligent transport systems},
keywords = {Driver behaviour },
abstract = {Abstract In this paper we study driver behaviour changes when driving vehicles equipped with Intelligent Speed Adaptation (ISA) systems. The primary tool used is a driving simulator. Three different \{ISA\} human machine interface functionalities are investigated: informative, warning, and intervening. Data were extracted from the simulator along with questionnaires completed by drivers following each drive. Possible impacts of system functionalities on driver behaviour are studied through appropriate metrics including driving speed, speed deviation, frequency and magnitude of speeding and the empirical cumulative distribution function of speeding. Perceived impacts on drivers are investigated to identify driver attitudes towards the systems as well as possible relations between anticipated and measured behaviour. The study indicates that use of \{ISA\} systems, in general, results in the adoption of vehicle speeds that are likely to improve road safety. However, we also found that drivers may misuse \{ISA\} systems, potentially resulting in negative road safety effects. }
}
@incollection{Kallioras2013345,
title = {15 - Scheduling Transportation Networks and Reliability Analysis of Geostructures Using Metaheuristics },
editor = {Alavi, Xin-She YangAmir Hossein GandomiSiamak TalatahariAmir Hossein },
booktitle = {Metaheuristics in Water, Geotechnical and Transport Engineering },
publisher = {Elsevier},
edition = {},
address = {Oxford},
year = {2013},
pages = {345 - 363},
isbn = {978-0-12-398296-4},
doi = {http://dx.doi.org/10.1016/B978-0-12-398296-4.00015-5},
url = {http://www.sciencedirect.com/science/article/pii/B9780123982964000155},
author = {Nikos Kallioras and George Piliounis and Matthew G. Karlaftis and Nikos D. Lagaros},
abstract = {Three decades ago, new families of computational methods, denoted as soft computing methods, were proposed. These methods are based on heuristic approaches rather than on rigorous mathematics. Despite the fact that these methods were initially received with suspicion, they have turned out in many cases to be surprisingly powerful, while their use in various areas of engineering science is continuously growing. Soft computing search algorithms such as evolutionary programming, genetic algorithms, and evolution strategies, among others, have been inspired by natural phenomena. Recently, new search algorithms have been proposed that are based on the simulation of social interactions between members of a specific species or algorithms inspired by the improvisation process of musicians. In this chapter, two optimization problems are considered for assessing the performance of metaheuristics. In particular, the problem of infrastructure network restoration and minimization of the adverse impacts of natural hazards on civil infrastructure and the problem of reliability analysis of geostructures, which is formulated as an optimization problem, are considered. Keywords Metaheuristics, districting problem, scheduling problem, emergency infrastructure inspection, piled foundation, reliability analysis }
}
@article{Milioti201488,
title = {Estimating multimodal public transport mode shares in Athens, Greece },
journal = {Journal of Transport Geography },
volume = {34},
number = {0},
pages = {88 - 95},
year = {2014},
note = {},
issn = {0966-6923},
doi = {http://dx.doi.org/10.1016/j.jtrangeo.2013.11.005},
url = {http://www.sciencedirect.com/science/article/pii/S0966692313002214},
author = {Christina P. Milioti and Matthew G. Karlaftis},
keywords = {Mode shares},
keywords = {Cointegration},
keywords = {Error correction},
keywords = {Multimodal},
keywords = {Public transport},
keywords = {Autocorrelation },
abstract = {Abstract We analyze market shares for each public transport mode in total public transport ridership for the multimodal public transportation system of Athens, Greece. This analysis provides useful information for making investment decisions concerning the public transport infrastructure and for allocating subsidies. Due to the non-stationary properties of the data, cointegration techniques are applied to investigate the long run equilibrium relationships. Error Correction Models are implemented to estimate short run dynamics as well as the speed of adjustment from the short to the long run. Results suggest that fare and \{GDP\} are the main determinants of the public transport mode shares both in the short and in the long run. Findings also indicate the role of total ridership fluctuations in explaining variations in public transport mode shares. }
}
@article{Christoforou201354,
title = {Reaction times of young alcohol-impaired drivers },
journal = {Accident Analysis & Prevention },
volume = {61},
number = {0},
pages = {54 - 62},
year = {2013},
note = {Emerging Research Methods and Their Application to Road Safety Emerging Issues in Safe and Sustainable Mobility for Older Persons The Candrive/Ozcandrive Prospective Older Driver Study: Methodology and Early Study Findings },
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2012.12.030},
url = {http://www.sciencedirect.com/science/article/pii/S0001457512004526},
author = {Zoi Christoforou and Matthew G. Karlaftis and George Yannis},
keywords = {Alcohol},
keywords = {Impaired driving},
keywords = {Reaction times},
keywords = {Simulator},
keywords = {Random-parameter regression },
abstract = {Young individuals who drive under the influence of alcohol have a higher relative risk of crash involvement; as such, the literature has extensively investigated the factors affecting such involvement through both post-accident surveys and simulator experiments. The effects of differentiated breath alcohol concentrations (BrAC) on young driver behavior, however, have been largely unaddressed, mainly as a result of the difficulty in collecting the necessary data. We explore young driver behavior under the influence of alcohol using a driving simulator experiment where 49 participants were subjected to a common pre-defined dose of alcohol consumption. Comparing reaction times before and after consumption allows for interesting insights and suggestions regarding policy interventions. As expected, the results indicate that increased reaction times before consuming alcohol strongly affect post-consumption reaction times, while increased BrAC levels prolong reaction times; a 10% increase in BrAC levels results in a 2% increase in reaction time. Interestingly, individuals with faster alcohol absorption times perform better regardless of absolute BrAC level, while recent meals lead to higher reaction times and regular exercising to lower. }
}
@article{Karlaftis2012392,
title = {Efficiency measurement in public transport: Are findings specification sensitive? },
journal = {Transportation Research Part A: Policy and Practice },
volume = {46},
number = {2},
pages = {392 - 402},
year = {2012},
note = {},
issn = {0965-8564},
doi = {http://dx.doi.org/10.1016/j.tra.2011.10.005},
url = {http://www.sciencedirect.com/science/article/pii/S0965856411001595},
author = {Matthew G. Karlaftis and Dimitrios Tsamboulas},
keywords = {Transit efficiency},
keywords = {Transit costs},
keywords = {Production functions},
keywords = {Transport performance },
abstract = {The need to measure transit system performance along with its various dimensions such as efficiency and effectiveness has led to the development of a wide array of approaches and vast literature. However, depending upon the specific approach used to examine performance, different conclusions are oftentimes reached. Using data from 15 European transit systems for a ten year time period (1990–2000), this paper discusses three important transit performance questions; (i) Do different efficiency assessment methodologies produce similar results? (ii) How are the two basic dimensions of transit performance, namely efficiency and effectiveness, related? and (iii) Are findings regarding organizational regimes (public operations, contracting and so on) sensitive to the methodological specifications employed? Results clearly indicate that efficiency scores and associated recommendations are sensitive to the models used, while efficiency and effectiveness are – albeit weakly – negatively related; these two findings can have far reaching policy implications. }
}
@article{Barnum20111160,
title = {Improving the efficiency of metropolitan area transit by joint analysis of its multiple providers },
journal = {Transportation Research Part E: Logistics and Transportation Review },
volume = {47},
number = {6},
pages = {1160 - 1176},
year = {2011},
note = {},
issn = {1366-5545},
doi = {http://dx.doi.org/10.1016/j.tre.2011.04.006},
url = {http://www.sciencedirect.com/science/article/pii/S1366554511000561},
author = {Darold T. Barnum and Matthew G. Karlaftis and Sonali Tandon},
keywords = {Data Envelopment Analysis},
keywords = {\{DEA\}},
keywords = {Technical efficiency},
keywords = {Allocation efficiency},
keywords = {Urban transit},
keywords = {Urban public transportation},
keywords = {Urban transport },
abstract = {Public transportation in a metropolitan area often is supplied by multiple types of transit. This paper develops and illustrates a DEA-based procedure for estimating: overall efficiency of an area’s public transportation; technical efficiencies of the individual transit types; effect of each type on overall efficiency; and efficiency of the allocation of resources among types and an algorithm for improving it. The paper concludes that the overall efficiency of an urban area’s public transportation can be validly estimated only if the technical efficiency of each major transport type and the efficiency in allocating resources among them are taken into consideration. }
}
@article{Christoforou20122454,
title = {Integrating Real-Time Traffic Data in Road Safety Analysis },
journal = {Procedia - Social and Behavioral Sciences },
volume = {48},
number = {0},
pages = {2454 - 2463},
year = {2012},
note = {Transport Research Arena 2012 },
issn = {1877-0428},
doi = {http://dx.doi.org/10.1016/j.sbspro.2012.06.1216},
url = {http://www.sciencedirect.com/science/article/pii/S187704281202959X},
author = {Zoi Christoforou and Simon Cohen and Matthew G. Karlaftis},
keywords = {Road safety},
keywords = {real-time traffic data},
keywords = {Probit},
keywords = {crash type},
keywords = {severity },
abstract = {Traffic data aggregation has been a serious factor of inaccuracy in most road safety studies. The Average Annual Daily Traffic (AADT) has been the most commonly used measure to reflect traffic conditions. In this paper, we establish a framework for the integration of real-time traffic data in road safety analysis. To this end, we explore the effects of traffic parameters on type of road crash and on the injury level sustained by vehicle occupants. Univariate and ordered Probit models are specified on 4-years of data from the A4-A86 highway section in the Ile-de-France region, France. Empirical results indicate that multi-vehicle crashes tend to occur under low or very high traffic speeds, while single-vehicle crashes appeared to be largely geometry-dependent. Increasing traffic volume was found to have a consistently positive (i.e. decreasing) effect on injury severity, while speed appears to have a differential effect on severity depending on flow conditions. Also, while in higher traffic volumes higher traffic speeds aggravate severity outcomes, in lower traffic volumes speed does not significantly influence severity in a consistent pattern. }
}
@article{Pyrialakou201233,
title = {Assessing operational efficiency of airports with high levels of low-cost carrier traffic },
journal = {Journal of Air Transport Management },
volume = {25},
number = {0},
pages = {33 - 36},
year = {2012},
note = {Notes },
issn = {0969-6997},
doi = {http://dx.doi.org/10.1016/j.jairtraman.2012.05.005},
url = {http://www.sciencedirect.com/science/article/pii/S0969699712000907},
author = {V. Dimitra Pyrialakou and Matthew G. Karlaftis and Panayotis G. Michaelides},
keywords = {Airport operational efficiency},
keywords = {Low-cost airlines},
keywords = {Airport use },
abstract = {The past few years have seen a significant increase in low-cost carrier traffic that has in several ways, affected airport operations. Only limited analysis, however, of the connection between airport efficiency and low-cost carriers has been conducted. We use data from 10 Greek airports that handle approximately 85% of low-cost carrier demand in the country, to investigate this connection. We find that low-cost carrier traffic, with its highly seasonal characteristics, significantly affects efficiency findings. }
}
@article{Skaltsas201346,
title = {An analysis of air traffic controller-pilot miscommunication in the NextGen environment },
journal = {Journal of Air Transport Management },
volume = {27},
number = {0},
pages = {46 - 51},
year = {2013},
note = {},
issn = {0969-6997},
doi = {http://dx.doi.org/10.1016/j.jairtraman.2012.11.010},
url = {http://www.sciencedirect.com/science/article/pii/S0969699712001536},
author = {Gerasimos Skaltsas and Jasenka Rakas and Matthew G. Karlaftis},
keywords = {Air traffic control},
keywords = {Data communications},
keywords = {Pilot behavior},
keywords = {NextGen },
abstract = {This paper extends research on miscommunication between air traffic controllers and pilots by developing statistical models that predict the outcome of communications within the scope of controller-pilot data communications in the Next Generation Air Transportation environment. A database of controller-pilot voice messages from high and super-high altitude en-route sectors of \{US\} airspace is investigated. Emphasis is given to parameters that can be utilized in the voice-only communication, as well as in the mixed media, environment. This allows formulation of reasonable assumptions about the impact of data communications on controller and pilot behavior. The models indicate that the most important factors affecting communications are length and context of the message, entering of an aircraft into a sector, transfer of communication, and radio frequency congestion. The results also suggest that the transmission of non-time critical routine messages via data communications could reduce the number of communication errors and alleviate radio frequency congestion. }
}
@article{Karlaftis2009444,
title = {Memory properties and fractional integration in transportation time-series },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {17},
number = {4},
pages = {444 - 453},
year = {2009},
note = {},
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/j.trc.2009.03.001},
url = {http://www.sciencedirect.com/science/article/pii/S0968090X09000254},
author = {Matthew G. Karlaftis and Eleni I. Vlahogianni},
keywords = {Transportation},
keywords = {Time-series},
keywords = {\{ARIMA\}},
keywords = {\{GARCH\}},
keywords = {Fractional integration },
abstract = {In transportation analyses, autoregressive integrated moving average (ARIMA) and generalized autoregressive conditional heteroskedasticity (GARCH) models have been widely used mainly because of their well established theoretical foundation and ease of application. However, they lack the ability to capture long memory properties and do not jointly treat the mean and variance (variability) of a time-series. We employ fractionally integrated dual memory models and compare results to classical time-series models in a traffic engineering context. Results indicate that dual memory models offer better representation of the original time-series than classical models; further, forcing the differentiation parameter of \{ARIMA\} model to equal 1 leads to over-inflated moving average terms and, consequently, to questionable models with artificial correlation structures. }
}
@article{Noland2005439,
title = {Sensitivity of crash models to alternative specifications },
journal = {Transportation Research Part E: Logistics and Transportation Review },
volume = {41},
number = {5},
pages = {439 - 458},
year = {2005},
note = {Road Safety, Alcohol and Public Policy },
issn = {1366-5545},
doi = {http://dx.doi.org/10.1016/j.tre.2005.03.002},
url = {http://www.sciencedirect.com/science/article/pii/S1366554505000244},
author = {Robert B. Noland and Matthew G. Karlaftis},
keywords = {Crash models},
keywords = {Negative binomial models},
keywords = {Count data},
keywords = {Policy analysis},
keywords = {Safety-belts},
keywords = {Drunk driving },
abstract = {This paper examines the sensitivity of policy conclusions that are derived from crash models using various specifications. Our analyses compare models specified as crash rate or population normalized models (i.e., fatalities per capita or per vehicle miles traveled) adjusted to account for serial correlation in the error term with negative binomial count models with the total number of fatalities as the dependent variable. Our analyses focus on the interpretation of key policy variables, especially the association between safety-belt laws and administrative license revocation laws on fatalities. Evaluation of statistical significance of parameters, elasticities derived from the models and total fatalities associated with changes in key variables are examined. Results suggest that negative binomial models tend to be more robust and display less variation in results than those linear regression models that account for serial correlation. From a policy perspective, we found no evidence that passage of administrative license revocation laws that automatically suspend the license of a drunk driver have been effective while laws requiring safety-belt usage have been effective. Our results suggest that providing confidence intervals on elasticity estimates and estimated fatalities would provide policy makers with greater confidence in the results of model estimates. }
}
@article{Karlaftis2010641,
title = {Applications of advanced technologies in transportation: Selected papers from the 10th \{AATT\} conference },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {18},
number = {5},
pages = {641 - 642},
year = {2010},
note = {Applications of Advanced Technologies in Transportation: Selected papers from the 10th \{AATT\} Conference },
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/j.trc.2009.12.001},
url = {http://www.sciencedirect.com/science/article/pii/S0968090X09001466},
author = {Matthew G. Karlaftis}
}
@article{Geroliminis2011287,
title = {A hybrid hypercube – Genetic algorithm approach for deploying many emergency response mobile units in an urban network },
journal = {European Journal of Operational Research },
volume = {210},
number = {2},
pages = {287 - 300},
year = {2011},
note = {},
issn = {0377-2217},
doi = {http://dx.doi.org/10.1016/j.ejor.2010.08.031},
url = {http://www.sciencedirect.com/science/article/pii/S0377221710005916},
author = {Nikolas Geroliminis and Konstantinos Kepaptsoglou and Matthew G. Karlaftis},
keywords = {Emergency response},
keywords = {Hypercube},
keywords = {Spatial queues},
keywords = {Genetic algorithms },
abstract = {Emergency response services are critical for modern societies. This paper presents a model and a heuristic solution for the optimal deployment of many emergency response units in an urban transportation network and an application for transit mobile repair units (TMRU) in the city of Athens, Greece. The model considers the stochastic nature of such services, suggesting that a unit may be already engaged, when an incident occurs. The proposed model integrates a queuing model (the hypercube model), a location model and a metaheuristic optimization algorithm (genetic algorithm) for obtaining appropriate unit locations in a two-step approach. In the first step, the service area is partitioned into sub-areas (called superdistricts) while, in parallel, necessary number of units is determined for each superdistrict. An approximate solution to the symmetric hypercube model with spatially homogeneous demand is developed. A Genetic Algorithm is combined with the approximate hypercube model for obtaining best superdistricts and associated unit numbers. With both of the above requirements defined in step one, the second step proceeds in the optimal deployment of units within each superdistrict. }
}
@article{Geroliminis2009798,
title = {A spatial queuing model for the emergency vehicle districting and location problem },
journal = {Transportation Research Part B: Methodological },
volume = {43},
number = {7},
pages = {798 - 811},
year = {2009},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/j.trb.2009.01.006},
url = {http://www.sciencedirect.com/science/article/pii/S0191261509000186},
author = {Nikolas Geroliminis and Matthew G. Karlaftis and Alexander Skabardonis},
keywords = {Emergency response},
keywords = {Accidents},
keywords = {Spatial queues},
keywords = {Location models },
abstract = {Emergency response systems in urban areas should be located to ensure adequate coverage and rapid response time. We develop a model for locating emergency vehicles on urban networks considering both spatial and temporal demand characteristics such as the probability that a server is not available when required. We also consider that service rates are not identical but may vary among servers and are dependent upon incident characteristics; corresponding districting and dispatching problems are also integrated in the location model. The model is applied using real data for locating freeway service patrol vehicles and results are compared with existing coverage and median models. Results show improvements in the mean response time particularly in cases of high demand for intervention when compared to ‘traditional’ models. }
}
@article{Christoforou20101606,
title = {Vehicle occupant injury severity on highways: An empirical investigation },
journal = {Accident Analysis & Prevention },
volume = {42},
number = {6},
pages = {1606 - 1620},
year = {2010},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2010.03.019},
url = {http://www.sciencedirect.com/science/article/pii/S0001457510001016},
author = {Zoi Christoforou and Simon Cohen and Matthew G. Karlaftis},
keywords = {Severity},
keywords = {Ordered probit},
keywords = {Random parameters},
keywords = {Safety },
abstract = {Accident severity analysis is important to both researchers and practitioners because of its implications in accident cost estimation, external cost estimation and road safety. Although much research has been done to explore the factors influencing crash-injury severity, few studies have investigated the association between severity and traffic characteristics collected real-time during the time the accident occurred. We apply a random parameters ordered probit model to explore the influence of speed and traffic volume on the injury level sustained by vehicle occupants involved in accidents on the A4–A86 junction in the Paris region. Results indicate that increased traffic volume has a consistently positive effect on severity, while speed has a differential effect on severity depending on flow conditions. }
}
@article{KEPAPTSOGLOU201053,
title = {Optimizing Pricing Policies in Park-and-Ride Facilities: A Model and Decision Support System with Application },
journal = {Journal of Transportation Systems Engineering and Information Technology },
volume = {10},
number = {5},
pages = {53 - 65},
year = {2010},
note = {},
issn = {1570-6672},
doi = {http://dx.doi.org/10.1016/S1570-6672(09)60063-5},
url = {http://www.sciencedirect.com/science/article/pii/S1570667209600635},
author = {Konstantinos KEPAPTSOGLOU and Matthew G KARLAFTIS and Zongzhi LI},
keywords = {urban traffic},
keywords = {park-and-ride},
keywords = {shared use},
keywords = {pricing policy},
keywords = {pricing scheme},
keywords = {optimization},
keywords = {genetic algorithm},
keywords = {decision support system },
abstract = {Park-and-ride facilities are of major importance to the attractiveness and operation of modern transit systems because travelers tend to prefer public transportation when they are able to combine the use of these facilities with their private vehicles. Among those elements examined when developing/operating a park-and-ride facility is the pricing policy to be established for its users. Indeed, the pricing policy is among those tools that can aid transportation agencies in managing park-and-ride facilities, by providing incentives or disincentives of parking for various categories of users. This paper contributes to the literature by offering a new approach for obtaining optimal pricing schemes for a parking facility, with respect to its financial viability. In particular, a financial analysis model is combined with a genetic algorithm for determining the optimal pricing parameters for park-and-ride facilities. The model is applied for a shared-use, park-and-ride facility of the Athens metro network in Greece. Results of the computational study indicate that the model can offer near optimal pricing schemes in a short amount of time. Also, a decision support system is developed for incorporating the model in a user friendly computerized framework. }
}
@article{Christoforou201143,
title = {Identifying crash type propensity using real-time traffic data on freeways },
journal = {Journal of Safety Research },
volume = {42},
number = {1},
pages = {43 - 50},
year = {2011},
note = {},
issn = {0022-4375},
doi = {http://dx.doi.org/10.1016/j.jsr.2011.01.001},
url = {http://www.sciencedirect.com/science/article/pii/S0022437511000065},
author = {Zoi Christoforou and Simon Cohen and Matthew G. Karlaftis},
keywords = {Traffic accident},
keywords = {Crash type},
keywords = {Multivariate Probit},
keywords = {Freeway },
abstract = {Introduction: We examine the effects of various traffic parameters on type of road crash. Method: Multivariate probit models are specified on 4-years of data from the A4-A86 highway section in the Ile-de-France region, France. Results: Empirical findings indicate that crash type can almost exclusively be defined by the prevailing traffic conditions shortly before its occurrence. Rear-end crashes involving two vehicles were found to be more probable for relatively low values of both speed and density, rear-end crashes involving more than two vehicles appear to be more probable under congested conditions, while single-vehicle crashes appear to be largely geometry-dependent. Impact on Industry: Results could be integrated in a real-time traffic management application. }
}
@article{Karlaftis2009210,
title = {Containership routing with time deadlines and simultaneous deliveries and pick-ups },
journal = {Transportation Research Part E: Logistics and Transportation Review },
volume = {45},
number = {1},
pages = {210 - 221},
year = {2009},
note = {},
issn = {1366-5545},
doi = {http://dx.doi.org/10.1016/j.tre.2008.05.001},
url = {http://www.sciencedirect.com/science/article/pii/S1366554508000963},
author = {Matthew G. Karlaftis and Konstantinos Kepaptsoglou and Evangelos Sambracos},
keywords = {Ship routing},
keywords = {Containerships},
keywords = {Pick-ups and deliveries},
keywords = {Time deadlines },
abstract = {In this paper we seek to determine optimal routes for a containership fleet performing pick-ups and deliveries between a hub and several spoke ports. A capacitated vehicle routing problem with pick-ups, deliveries and time deadlines is formulated and solved using a hybrid genetic algorithm for establishing routes for a dedicated containership fleet. Results on the performance of the algorithm and the feasibility of the approach show that a relatively small fleet of containerships could provide efficient services within deadlines. Moreover, through sensitivity analysis we discuss performance robustness and consistency of the developed algorithm under a variety of problem settings and parameters values. }
}
@article{Karlaftis2003225,
title = {Investigating transit production and performance: a programming approach },
journal = {Transportation Research Part A: Policy and Practice },
volume = {37},
number = {3},
pages = {225 - 240},
year = {2003},
note = {},
issn = {0965-8564},
doi = {http://dx.doi.org/10.1016/S0965-8564(02)00013-7},
url = {http://www.sciencedirect.com/science/article/pii/S0965856402000137},
author = {Matthew G. Karlaftis},
keywords = {Transit efficiency},
keywords = {Transit economics and production},
keywords = {Data envelopment analysis},
keywords = {Mathematical programming },
abstract = {Although efficiency and productivity are closely related issues, they have been generally examined separately in the transit literature. Using an extensive panel data set, this analysis extends prior research in two directions. First, efficiency rankings and efficient subsets of transit systems are obtained through data envelopment analysis (DEA), a non-parametric linear programming based methodology. Second, based on the results of the \{DEA\} analysis, globally efficient frontier production functions, in the context of transit operations in the United States, are built. The results indicate that when jointly considered, there is an improvement on both the theoretical and empirical aspects of examining efficiency and production in transit systems. Further, the results indicate that efficiency and returns to scale findings differ substantially depending on the evaluation methodology used. }
}
@article{Vlahogianni2005211,
title = {Optimized and meta-optimized neural networks for short-term traffic flow prediction: A genetic approach },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {13},
number = {3},
pages = {211 - 234},
year = {2005},
note = {},
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/j.trc.2005.04.007},
url = {http://www.sciencedirect.com/science/article/pii/S0968090X05000276},
author = {Eleni I. Vlahogianni and Matthew G. Karlaftis and John C. Golias},
keywords = {Traffic flow},
keywords = {Multivariate time series},
keywords = {Short-term predictions},
keywords = {Neural networks},
keywords = {Genetic optimization },
abstract = {Short-term forecasting of traffic parameters such as flow and occupancy is an essential element of modern Intelligent Transportation Systems research and practice. Although many different methodologies have been used for short-term predictions, literature suggests neural networks as one of the best alternatives for modeling and predicting traffic parameters. However, because of limited knowledge regarding a network’s optimal structure given a specific dataset, researchers have to rely on time consuming and questionably efficient rules-of-thumb when developing them. This paper extends past research by providing an advanced, genetic algorithm based, multilayered structural optimization strategy that can assist both in the proper representation of traffic flow data with temporal and spatial characteristics as well as in the selection of the appropriate neural network structure. Further, it evaluates the performance of the developed network by applying it to both univariate and multivariate traffic flow data from an urban signalized arterial. The results show that the capabilities of a simple static neural network, with genetically optimized step size, momentum and number of hidden units, are very satisfactory when modeling both univariate and multivariate traffic data. }
}
@article{Stathopoulos2003121,
title = {A multivariate state space approach for urban traffic flow modeling and prediction },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {11},
number = {2},
pages = {121 - 135},
year = {2003},
note = {},
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/S0968-090X(03)00004-4},
url = {http://www.sciencedirect.com/science/article/pii/S0968090X03000044},
author = {Anthony Stathopoulos and Matthew G. Karlaftis},
keywords = {Traffic flow},
keywords = {Multivariate time series},
keywords = {Short-term predictions },
abstract = {Urban traffic congestion is one of the most severe problems of everyday life in Metropolitan areas. In an effort to deal with this problem, intelligent transportation systems (ITS) technologies have concentrated in recent years on dealing with urban congestion. One of the most critical aspects of \{ITS\} success is the provision of accurate real-time information and short-term predictions of traffic parameters such as traffic volumes, travel speeds and occupancies. The present paper concentrates on developing flexible and explicitly multivariate time-series state space models using core urban area loop detector data. Using 3-min volume measurements from urban arterial streets near downtown Athens, models were developed that feed on data from upstream detectors to improve on the predictions of downstream locations. The results clearly suggest that different model specifications are appropriate for different time periods of the day. Further, it also appears that the use of multivariate state space models improves on the prediction accuracy over univariate time series ones. }
}
@article{Karlaftis2003207,
title = {An empirical investigation of European drivers' self-assessment },
journal = {Journal of Safety Research },
volume = {34},
number = {2},
pages = {207 - 213},
year = {2003},
note = {},
issn = {0022-4375},
doi = {http://dx.doi.org/10.1016/S0022-4375(03)00009-4},
url = {http://www.sciencedirect.com/science/article/pii/S0022437503000094},
author = {Matthew G. Karlaftis and Ioannis Kotzampassakis and George Kanellaidis},
keywords = {Traffic safety},
keywords = {Self-assessment},
keywords = {\{SARTRE\} },
abstract = {Problem: Evaluating motorists through self-assessment has attracted much interest in recent literature, which is mainly due to the profound impact various parameters of self-assessment can have on the way motorists deal with hazardous traffic situations. Much of the previous work in this area has been hampered both by the lack of adequate sample sizes and, because of the small samples, the evaluation methodologies used. Method: This paper extends previous research in two significant directions: (a) it uses the \{SARTRE\} 2 database, which provides more than 17,000 questionnaires from most European countries; and (b) it employs the ordered probit modeling approach, which recognizes the latent nature of self-assessment and explicitly links its dimensions to a set of relevant explanatory variables such as age, gender, region, and income. Results: The results indicate that drivers who rate themselves as both more dangerous and faster than others are, generally, younger men, with higher incomes, break the speed limit more frequently, avoid wearing seat belts, and have been involved in more accidents in the past than other drivers. Interestingly, more experienced and more highly educated drivers assess their driving as less dangerous, but admit to driving faster than other drivers. Impact on Industry: The methodology used and the results obtained can be a significant help in identifying drivers with high and low self-assessment ratings, which can be useful in planning and implementing road safety information campaigns. }
}
@article{Karlaftis2004354,
title = {A \{DEA\} approach for evaluating the efficiency and effectiveness of urban transit systems },
journal = {European Journal of Operational Research },
volume = {152},
number = {2},
pages = {354 - 364},
year = {2004},
note = {New Technologies in Transportation Systems },
issn = {0377-2217},
doi = {http://dx.doi.org/10.1016/S0377-2217(03)00029-8},
url = {http://www.sciencedirect.com/science/article/pii/S0377221703000298},
author = {Matthew G Karlaftis},
keywords = {Transit performance},
keywords = {Data envelopment analysis},
keywords = {Efficiency and effectiveness },
abstract = {The need to measure transit system performance along with its various dimensions has led to the development of a large number of quantitative performance indicators. However, depending upon the specific indicator examined, different conclusions can oftentimes be reached regarding performance. Further, although performance and scale economies are closely related issues, they have been generally examined separately in the transit literature. The research reported in this paper uses data envelopment analysis and globally efficient frontier production functions to investigate two important issues in transit operations: first, the relationship between the two basic dimensions of performance, namely efficiency and effectiveness; second, the relationship between performance and scale economies. Using data from 256 \{US\} transit systems over a five-year period the results indicate that efficiency and effectiveness are positively related. Further, they imply that the magnitude of scale economies depends on the output specification. }
}
@article{Karlaftis20021,
title = {Cost structures of public transit systems: a panel data analysis },
journal = {Transportation Research Part E: Logistics and Transportation Review },
volume = {38},
number = {1},
pages = {1 - 18},
year = {2002},
note = {},
issn = {1366-5545},
doi = {http://dx.doi.org/10.1016/S1366-5545(01)00006-0},
url = {http://www.sciencedirect.com/science/article/pii/S1366554501000060},
author = {Matthew G. Karlaftis and Patrick McCarthy},
keywords = {Public transit},
keywords = {Cost structures},
keywords = {Translog},
keywords = {System size},
keywords = {Section 15},
keywords = {Cluster analysis },
abstract = {Results from numerous cost studies have generated conflicting results on public transit production technologies. Because prior studies have employed various sub-samples of public transit properties, the diverse results may either reflect alternative technologies or sampling differences. Based on a panel of nearly all transit systems reporting for Section 15 (US National Transit Data) purposes from 1986 to 1994, this paper explores whether public transit production technology differs by size and operating characteristics of the system. The results indicate that \{US\} transit properties are heterogeneous with different production technologies, which implies that transit cost analyses based upon a set of heterogeneous systems will generate incorrect inferences on public transit cost and production structures. }
}
@article{Karlaftis2002357,
title = {Effects of road geometry and traffic volumes on rural roadway accident rates },
journal = {Accident Analysis & Prevention },
volume = {34},
number = {3},
pages = {357 - 365},
year = {2002},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/S0001-4575(01)00033-1},
url = {http://www.sciencedirect.com/science/article/pii/S0001457501000331},
author = {Matthew G Karlaftis and Ioannis Golias},
keywords = {Accident rates},
keywords = {Rural roads},
keywords = {Hierarchical tree based regression },
abstract = {This paper revisits the question of the relationship between rural road geometric characteristics, accident rates and their prediction, using a rigorous non-parametric statistical methodology known as hierarchical tree-based regression. The goal of this paper is twofold; first, it develops a methodology that quantitatively assesses the effects of various highway geometric characteristics on accident rates and, second, it provides a straightforward, yet fundamentally and mathematically sound way of predicting accident rates on rural roads. The results show that although the importance of isolated variables differs between two-lane and multilane roads, ‘geometric design’ variables and ‘pavement condition’ variables are the two most important factors affecting accident rates. Further, the methodology used in this paper allows for the explicit prediction of accident rates for given highway sections, as soon as the profile of a road section is given. }
}
@article{Vlahogianni2006351,
title = {Statistical methods for detecting nonlinearity and non-stationarity in univariate short-term time-series of traffic volume },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {14},
number = {5},
pages = {351 - 367},
year = {2006},
note = {},
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/j.trc.2006.09.002},
url = {http://www.sciencedirect.com/science/article/pii/S0968090X06000696},
author = {Eleni I. Vlahogianni and Matthew G. Karlaftis and John C. Golias},
keywords = {Traffic volume},
keywords = {Signalized arterials},
keywords = {Short-term prediction},
keywords = {Nonlinearity},
keywords = {Non-stationarity},
keywords = {State-space reconstruction},
keywords = {Recurrence plots},
keywords = {Recurrence quantification analysis },
abstract = {Short-term traffic volume data are characterized by rapid and intense fluctuations with frequent shifts to congestion. Currently, research in short-term traffic forecasting deals with these phenomena either by smoothing them or by accounting for them by nonlinear models. But, these approaches lead to inefficient predictions particularly when the data exhibit intense oscillations or frequent shifts to boundary conditions (congestion). This paper offers a set of tools and methods to assess on underlying statistical properties of short-term traffic volume data, a topic that has largely been overlooked in traffic forecasting literature. Results indicate that the statistical characteristics of traffic volume can be identified from prevailing traffic conditions; for example, volume data exhibit frequent shifts from deterministic to stochastic structures as well as transitions between cyclic and strongly nonlinear behaviors. These findings could be valuable in the implementation of a variable prediction strategy according to the statistical characteristics of the prevailing traffic volume states. }
}
@article{Golias2001243,
title = {An international comparative study of self-reported driver behavior },
journal = {Transportation Research Part F: Traffic Psychology and Behaviour },
volume = {4},
number = {4},
pages = {243 - 256},
year = {2001},
note = {},
issn = {1369-8478},
doi = {http://dx.doi.org/10.1016/S1369-8478(01)00026-2},
url = {http://www.sciencedirect.com/science/article/pii/S1369847801000262},
author = {Ioannis Golias and Matthew G Karlaftis},
keywords = {Self-reported behavior},
keywords = {Regression trees},
keywords = {European drivers },
abstract = {Using a large data base of 20,725 questionnaires from 19 European countries, this article uses a combination of factor analysis and tree based regression to determine driver groups with homogeneous self-reported behavior and determine whether regional differences in driving behaviors exist. Self-reported behavior, including speeding, reckless driving, seat belt use, and drinking and driving are examined. The results suggest that speeding and general reckless (dangerous) behavior are related, perhaps capturing a driver's “risk taking” or “pre-trip violations” behavior. Similarly, seat belt use and driving under the influence of alcohol are also related and may represent a driver's “law abiding” tendency or “during-trip violations” behavior. Further, important regional differences and similarities between European drivers are uncovered. Northern European drivers report a significantly higher compliance with drinking and driving laws and seat belt use regulations than do Southern and Eastern European drivers. }
}
@article{Karlaftis1998425,
title = {Heterogeneity considerations in accident modeling },
journal = {Accident Analysis & Prevention },
volume = {30},
number = {4},
pages = {425 - 433},
year = {1998},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/S0001-4575(97)00122-X},
url = {http://www.sciencedirect.com/science/article/pii/S000145759700122X},
author = {Matthew G. Karlaftis and Andrzej P. Tarko},
keywords = {Accident modeling},
keywords = {Clustering},
keywords = {Heterogeneity},
keywords = {Negative binomial models },
abstract = {Panel data sets are becoming readily available and increasingly popular in safety research. Despite its advantages, panel data raises new specification issues, the most important of which is heterogeneity, which have not been addressed in previous studies in the safety area. Based on a county accident data set, the present analysis extends prior research in a significant direction. There is an explicit effort to control for cross-section heterogeneity that may otherwise seriously bias the resulting estimates and invalidate statistical tests. Because common modeling techniques such as the fixed and random effects models, developed to account for heterogeneity, are impractical for count data, this study uses cluster analysis to overcome this. First, observations are disaggregated into homogeneous clusters. Then, separate negative binomial models including a time trend factor are developed for each group. The results clearly indicate that there are significant differences between the models developed, and that separate models describe data more efficiently than the joint model. }
}
@comment{{Sivaramakrishnan Srinivasan papers}}
@article{Alivand201541,
title = {Analyzing how travelers choose scenic routes using route choice models },
journal = {Computers, Environment and Urban Systems },
volume = {50},
number = {0},
pages = {41 - 52},
year = {2015},
note = {},
issn = {0198-9715},
doi = {http://dx.doi.org/10.1016/j.compenvurbsys.2014.10.004},
url = {http://www.sciencedirect.com/science/article/pii/S0198971514001136},
author = {Majid Alivand and Hartwig Hochmair and Sivaramakrishnan Srinivasan},
keywords = {Scenic route},
keywords = {\{VGI\}},
keywords = {Route choice model},
keywords = {Viewshed analysis},
keywords = {Geo-tagged photos},
keywords = {Path Size Logit },
abstract = {Abstract Finding a scenic route between two locations is a common trip planning task, in particular for tourists and recreational travelers. For the automated computation of a scenic route in a trip planning system it is necessary to identify which attributes of a route and its surroundings are associated with attractive scenery. This study uses a route choice model, more specifically a Path Size Logit (PSL) model, to identify the relevant attributes and their relative importance. Three hypotheses are formulated and tested with three \{PSL\} models to understand the effects of different attributes on scenic route selection. The set of chosen scenic routes are based on various \{VGI\} (Volunteered Geographic Information) data that have been extracted for California as a study region. The results identify several variables of the surrounding environment as significant contributors to route scenery after controlling for road type. }
}
@article{Zhu20111427,
title = {Modeling occupant-level injury severity: An application to large-truck crashes },
journal = {Accident Analysis & Prevention },
volume = {43},
number = {4},
pages = {1427 - 1437},
year = {2011},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2011.02.021},
url = {http://www.sciencedirect.com/science/article/pii/S000145751100042X},
author = {Xiaoyu Zhu and Sivaramakrishnan Srinivasan},
keywords = {Occupant-level injury severity},
keywords = {Mixed ordered-probit models},
keywords = {Large-truck crashes },
abstract = {Most of the injury-severity analyses to date have focused primarily on modeling the most-severe injury of any crash, although a substantial fraction of crashes involve multiple vehicles and multiple persons. In this study, we present an extensive exploratory analysis that highlights that the highest injury severity is not necessarily the comprehensive indicator of the overall severity of any crash. Subsequently, we present a panel, hetroskedastic ordered-probit model to simultaneously analyze the injury severities of all persons involved in a crash. The models are estimated in the context of large-truck crashes. The results indicate strong effects of person-, driver-, vehicle-, and crash-characteristics on the injury severities of persons involved in large-truck crashes. For example, several driver behavior characteristics (such as use of illegal drugs, DUI, and inattention) were found to be statistically significant predictors of injury severity. The availability of airbags and the use of seat-belts are also found to be associated with less-severe injuries to car-drivers and car-passengers in the event of crashes with large trucks. Car drivers’ familiarity with the vehicle and the roadway are also important for both the car drivers and passengers. Finally, the models also indicate the strong presence of intra-vehicle correlations (effect of common vehicle-specific unobserved factors) among the injury propensities of all persons within a vehicle. }
}
@article{Zhu201149,
title = {A comprehensive analysis of factors influencing the injury severity of large-truck crashes },
journal = {Accident Analysis & Prevention },
volume = {43},
number = {1},
pages = {49 - 57},
year = {2011},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2010.07.007},
url = {http://www.sciencedirect.com/science/article/pii/S0001457510001958},
author = {Xiaoyu Zhu and Sivaramakrishnan Srinivasan},
keywords = {Large-truck crash},
keywords = {Injury severity measures},
keywords = {\{LTCCS\}},
keywords = {Ordered-probit model },
abstract = {Given the importance of trucking to the economic well being of a country and the safety concerns posed by the trucks, a study of large-truck crashes is critical. This paper contributes by undertaking an extensive analysis of the empirical factors affecting injury severity of large-truck crashes. Data from a recent, nationally representative sample of large-truck crashes are examined to determine the factors affecting the overall injury severity of these crashes. The explanatory factors include the characteristics of the crash, vehicle(s), and the driver(s). The injury severity was modeled using two measures. Several similarities and some differences were observed across the two models which underscore the need for improved accuracy in the assessment of injury severity of crashes. The estimated models capture the marginal effects of a variety of explanatory factors simultaneously. In particular, the models indicate the impacts of several driver behavior variables on the severity of the crashes, after controlling for a variety of other factors. For example, driver distraction (truck drivers), alcohol use (car drivers), and emotional factors (car drivers) are found to be associated with higher severity crashes. A further interesting finding is the strong statistical significance of several dummy variables that indicate missing data – these reflect how the nature of the crash itself could affect the completeness of the data. Future efforts should seek to collect such data more comprehensively so that the true effects of these aspects on the crash severity can be determined. }
}
@article{Langford20081996,
title = {In defence of the ‘low-mileage bias’ },
journal = {Accident Analysis & Prevention },
volume = {40},
number = {6},
pages = {1996 - 1999},
year = {2008},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2008.08.027},
url = {http://www.sciencedirect.com/science/article/pii/S000145750800167X},
author = {Jim Langford and Sjaanie Koppel and Dennis McCarthy and Sivaramakrishnan Srinivasan},
keywords = {Older drivers},
keywords = {Crash risk},
keywords = {Low-mileage bias },
abstract = {There has been a long-recognised association between extent of driving and crash involvement: the lower the annual mileage driven, the higher the per-distance crash rate. Because older drivers generally drive less distance per year than others, this association has been used to explain much of their apparent over-involvement in crashes. Several studies from different countries around the world have demonstrated this ‘low-mileage bias’ and the relative safety of older drivers. However all studies have relied upon self-reported crash involvement and driving activity. Staplin et al. [Staplin, L., Gish, K., Joyce, J., 2008. ‘Low mileage bias’ and related policy implications—a cautionary note. Accident Analysis and Prevention 40, 1249–1252] have drawn attention to the discrepancy between self-reported and odometer-based driving distances and have argued against the credibility of the low-mileage bias. This paper has re-worked initial data from an early study which supported low-mileage bias, this time using odometer-based readings rather than self-reported mileage. Accepting the odometer readings at face value, the low-mileage bias remains evident, albeit at a reduced level. }
}
@comment{{Simon Washington papers}}
@article{Whitehead2015250,
title = {Transitioning to energy efficient vehicles: An analysis of the potential rebound effects and subsequent impact upon emissions },
journal = {Transportation Research Part A: Policy and Practice },
volume = {74},
number = {0},
pages = {250 - 267},
year = {2015},
note = {},
issn = {0965-8564},
doi = {http://dx.doi.org/10.1016/j.tra.2015.02.016},
url = {http://www.sciencedirect.com/science/article/pii/S0965856415000336},
author = {Jake Whitehead and Joel P. Franklin and Simon Washington},
keywords = {Energy efficient vehicles},
keywords = {Vehicle usage},
keywords = {Rebound effects},
keywords = {Propensity score matching},
keywords = {Congestion pricing},
keywords = {Vehicle emissions },
abstract = {Abstract Given the shift toward energy efficient vehicles (EEVs) in recent years, it is important that the effects of this transition are properly examined. This paper investigates some of these effects by analyzing annual kilometers traveled (AKT) of private vehicle owners in Stockholm in 2008. The difference in emissions associated with \{EEV\} adoption is estimated, along with the effect of a congestion-pricing exemption for \{EEVs\} on vehicle usage. Propensity score matching is used to compare \{AKT\} rates of different vehicle owner groups based on the treatments of: \{EEV\} ownership and commuting across the cordon, controlling for confounding factors such as demographics. Through this procedure, rebound effects are identified, with some \{EEV\} owners found to have driven up to 12.2% further than non-EEV owners. Although some of these differences could be attributed to the congestion-pricing exemption, the results were not statistically significant. Overall, taking into account lifecycle emissions of each fuel type, average \{EEV\} emissions were 50.5% less than average non-EEV emissions, with this reduction in emissions offset by 2.0% due to rebound effects. Although it is important for policy-makers to consider the potential for unexpected negative effects in similar transitions, the overall benefit of greatly reduced emissions appears to outweigh any rebound effects present in this case study. }
}
@article{Whitehead201424,
title = {The impact of a congestion pricing exemption on the demand for new energy efficient vehicles in Stockholm },
journal = {Transportation Research Part A: Policy and Practice },
volume = {70},
number = {0},
pages = {24 - 40},
year = {2014},
note = {},
issn = {0965-8564},
doi = {http://dx.doi.org/10.1016/j.tra.2014.09.013},
url = {http://www.sciencedirect.com/science/article/pii/S0965856414002328},
author = {Jake Whitehead and Joel P. Franklin and Simon Washington},
keywords = {Energy efficient vehicles},
keywords = {Congestion pricing},
keywords = {Incentive policies},
keywords = {Revealed preferences},
keywords = {Multinomial logit },
abstract = {Abstract As governments seek to transition to more efficient vehicle fleets, one strategy has been to incentivize ‘green’ vehicle choice by exempting some of these vehicles from road user charges. As an example, to stimulate sales of energy efficient vehicles (EEVs) in Sweden, some of these automobiles were exempted from Stockholm’s congestion tax. In this paper the effect this policy had on the demand for new, privately-owned, exempt \{EEVs\} is assessed by first estimating a model of vehicle choice and then by applying this model to simulate vehicle alternative market shares under different policy scenarios. The database used to calibrate the model includes owner-specific demographics merged with vehicle registry data for all new private vehicles registered in Stockholm County during 2008. Characteristics of individuals with a higher propensity to purchase an exempt \{EEV\} were identified. The most significant factors included intra-cordon residency (positive), distance from home to the \{CBD\} (negative), and commuting across the cordon (positive). By calculating vehicle shares from the vehicle choice model and then comparing these estimates to a simulated scenario where the congestion tax exemption was inactive, the exemption was estimated to have substantially increased the share of newly purchased, private, exempt \{EEVs\} in Stockholm by 1.8% (±0.3%; 95% C.I.) to a total share of 18.8%. This amounts to an estimated 10.7% increase in private, exempt \{EEV\} purchases during 2008, i.e., 519 privately owned, exempt EEVs. }
}
@article{Ye2009443,
title = {A simultaneous equations model of crash frequency by collision type for rural intersections },
journal = {Safety Science },
volume = {47},
number = {3},
pages = {443 - 452},
year = {2009},
note = {},
issn = {0925-7535},
doi = {http://dx.doi.org/10.1016/j.ssci.2008.06.007},
url = {http://www.sciencedirect.com/science/article/pii/S0925753508000933},
author = {Xin Ye and Ram M. Pendyala and Simon P. Washington and Karthik Konduri and Jutaek Oh},
keywords = {Intersection safety},
keywords = {Crash frequency},
keywords = {Collision type},
keywords = {Simultaneous equations model},
keywords = {Multivariate Poisson regression},
keywords = {Unobserved heterogeneity },
abstract = {Safety at roadway intersections is of significant interest to transportation professionals due to the large number of intersections in transportation networks, the complexity of traffic movements at these locations that leads to large numbers of conflicts, and the wide variety of geometric and operational features that define them. A variety of collision types including head-on, sideswipe, rear-end, and angle crashes occur at intersections. While intersection crash totals may not reveal a site deficiency, over exposure of a specific crash type may reveal otherwise undetected deficiencies. Thus, there is a need to be able to model the expected frequency of crashes by collision type at intersections to enable the detection of problems and the implementation of effective design strategies and countermeasures. Statistically, it is important to consider modeling collision type frequencies simultaneously to account for the possibility of common unobserved factors affecting crash frequencies across crash types. In this paper, a simultaneous equations model of crash frequencies by collision type is developed and presented using crash data for rural intersections in Georgia. The model estimation results support the notion of the presence of significant common unobserved factors across crash types, although the impact of these factors on parameter estimates is found to be rather modest. }
}
@article{Shin2009393,
title = {Evaluation of the Scottsdale Loop 101 automated speed enforcement demonstration program },
journal = {Accident Analysis & Prevention },
volume = {41},
number = {3},
pages = {393 - 403},
year = {2009},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2008.12.011},
url = {http://www.sciencedirect.com/science/article/pii/S000145750800242X},
author = {Kangwon Shin and Simon P. Washington and Ida van Schalkwyk},
keywords = {Safety},
keywords = {Speeding},
keywords = {Automated speed enforcement},
keywords = {Before-after},
keywords = {Empirical Bayes analysis},
keywords = {Freeway safety },
abstract = {Speeding is recognized as a major contributing factor in traffic crashes. In order to reduce speed-related crashes, the city of Scottsdale, Arizona implemented the first fixed-camera photo speed enforcement program (SEP) on a limited access freeway in the US. The 9-month demonstration program spanning from January 2006 to October 2006 was implemented on a 6.5 mile urban freeway segment of Arizona State Route 101 running through Scottsdale. This paper presents the results of a comprehensive analysis of the impact of the \{SEP\} on speeding behavior, crashes, and the economic impact of crashes. The impact on speeding behavior was estimated using generalized least square estimation, in which the observed speeds and the speeding frequencies during the program period were compared to those during other periods. The impact of the \{SEP\} on crashes was estimated using 3 evaluation methods: a before-and-after (BA) analysis using a comparison group, a \{BA\} analysis with traffic flow correction, and an empirical Bayes \{BA\} analysis with time-variant safety. The analysis results reveal that speeding detection frequencies (speeds ‚â• 76 mph) increased by a factor of 10.5 after the \{SEP\} was (temporarily) terminated. Average speeds in the enforcement zone were reduced by about 9 mph when the \{SEP\} was implemented, after accounting for the influence of traffic flow. All crash types were reduced except rear-end crashes, although the estimated magnitude of impact varies across estimation methods (and their corresponding assumptions). When considering Arizona-specific crash related injury costs, the \{SEP\} is estimated to yield about $17 million in annual safety benefits. }
}
@article{Oh2006346,
title = {Accident prediction model for railway-highway interfaces },
journal = {Accident Analysis & Prevention },
volume = {38},
number = {2},
pages = {346 - 356},
year = {2006},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2005.10.004},
url = {http://www.sciencedirect.com/science/article/pii/S0001457505001776},
author = {Jutaek Oh and Simon P. Washington and Doohee Nam},
keywords = {Railroad crossings},
keywords = {Poisson},
keywords = {Gamma},
keywords = {Negative binomial},
keywords = {International comparison },
abstract = {Considerable past research has explored relationships between vehicle accidents and geometric design and operation of road sections, but relatively little research has examined factors that contribute to accidents at railway-highway crossings. Between 1998 and 2002 in Korea, about 95% of railway accidents occurred at highway-rail grade crossings, resulting in 402 accidents, of which about 20% resulted in fatalities. These statistics suggest that efforts to reduce crashes at these locations may significantly reduce crash costs. The objective of this paper is to examine factors associated with railroad crossing crashes. Various statistical models are used to examine the relationships between crossing accidents and features of crossings. The paper also compares accident models developed in the United States and the safety effects of crossing elements obtained using Korea data. Crashes were observed to increase with total traffic volume and average daily train volumes. The proximity of crossings to commercial areas and the distance of the train detector from crossings are associated with larger numbers of accidents, as is the time duration between the activation of warning signals and gates. The unique contributions of the paper are the application of the gamma probability model to deal with underdispersion and the insights obtained regarding railroad crossing related vehicle crashes. }
}
@article{Cheng2005870,
title = {Experimental evaluation of hotspot identification methods },
journal = {Accident Analysis & Prevention },
volume = {37},
number = {5},
pages = {870 - 881},
year = {2005},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2005.04.015},
url = {http://www.sciencedirect.com/science/article/pii/S0001457505000667},
author = {Wen Cheng and Simon P. Washington},
keywords = {Safety},
keywords = {Sites with promise},
keywords = {Empirical Bayesian analysis},
keywords = {Crash history},
keywords = {Hot spot identification },
abstract = {Identifying crash “hotspots”, “blackspots”, “sites with promise”, or “high risk” locations is standard practice in departments of transportation throughout the US. The literature is replete with the development and discussion of statistical methods for hotspot identification (HSID). Theoretical derivations and empirical studies have been used to weigh the benefits of various \{HSID\} methods; however, a small number of studies have used controlled experiments to systematically assess various methods. Using experimentally derived simulated data—which are argued to be superior to empirical data, three hot spot identification methods observed in practice are evaluated: simple ranking, confidence interval, and Empirical Bayes. Using simulated data, sites with promise are known a priori, in contrast to empirical data where high risk sites are not known for certain. To conduct the evaluation, properties of observed crash data are used to generate simulated crash frequency distributions at hypothetical sites. A variety of factors is manipulated to simulate a host of ‘real world’ conditions. Various levels of confidence are explored, and false positives (identifying a safe site as high risk) and false negatives (identifying a high risk site as safe) are compared across methods. Finally, the effects of crash history duration in the three \{HSID\} approaches are assessed. The results illustrate that the Empirical Bayes technique significantly outperforms ranking and confidence interval techniques (with certain caveats). As found by others, false positives and negatives are inversely related. Three years of crash history appears, in general, to provide an appropriate crash history duration. }
}
@comment{{Satish Ukkusuri Papers}}
@article{Aziz2015121,
title = {Understanding short-term travel behavior under personal mobility credit allowance scheme using experimental economics },
journal = {Transportation Research Part D: Transport and Environment },
volume = {36},
number = {0},
pages = {121 - 137},
year = {2015},
note = {},
issn = {1361-9209},
doi = {http://dx.doi.org/10.1016/j.trd.2015.02.015},
url = {http://www.sciencedirect.com/science/article/pii/S1361920915000243},
author = {H.M. Abdul Aziz and Satish V. Ukkusuri and Julian Romero},
keywords = {Personal mobility carbon allowance},
keywords = {Low carbon living},
keywords = {Experimental games},
keywords = {Travel behavior},
keywords = {Market mechanisms},
keywords = {Carbon cap},
keywords = {Econometric model },
abstract = {Abstract This study proposes personal mobility carbon allowance scheme, collects the data using an online experimental game, and analyzes data with econometric models. Personal mobility carbon allowance (PMCA) schemes allocate carbon credits to users at no cost based on the emissions reduction goal of the system. Users spend carbon credits for travel and a market place exists where users can buy or sell credits. To understand this process, a real-time experimental game tool is developed where players are asked to make travel decisions within the carbon budget set by \{PMCA\} and they are allowed to trade carbon credits in a market modeled as a double auction game. Results from estimated random parameter models show that medium and low income group users are highly sensitive to increase in carbon cost for grocery (non-work) trips. Further, the elasticity values show that high income group are less sensitive to carbon cost increase for work trips. The market dynamics such as number of total bids or asks are examined through count data models. The insights from the models can be used to effectively design the parameters of \{PMCA\} schemes. In addition, the experimental game tool and the analysis framework can be applied to understand other market based strategies such as carbon tax and tradable emissions permits. }
}
@article{Qian201531,
title = {Spatial variation of the urban taxi ridership using \{GPS\} data },
journal = {Applied Geography },
volume = {59},
number = {0},
pages = {31 - 42},
year = {2015},
note = {},
issn = {0143-6228},
doi = {http://dx.doi.org/10.1016/j.apgeog.2015.02.011},
url = {http://www.sciencedirect.com/science/article/pii/S0143622815000429},
author = {Xinwu Qian and Satish V. Ukkusuri},
keywords = {Geographical weighted regression},
keywords = {Taxicab},
keywords = {Big data},
keywords = {Spatial variations},
keywords = {Urban trips },
abstract = {Abstract Taxicab is an important component of urban transit system since it caters to a large amount of demand and covers a wide geographic area. In this paper, we understand the spatial variation of urban taxi ridership using large scale New York City (NYC) taxi data. The taxi ridership is analyzed by relating it to various spatially explicit socio-demographic and built-environment variables. The geographically weighted regression (GWR) is implemented to model the spatial heterogeneity of the taxi ridership and visualize the spatial distributions of parameter estimations. The results suggest that the \{GWR\} model outperforms the ordinary least square model in both goodness of model fit and explanatory accuracy. The urban form is revealed to have significant impact on urban taxi ridership and strong spatial variability for parameter estimations is observed. Medium income level is found to reduce the number of taxi trips at particular places and the accessibility to subways is positively associated with the taxi ridership. The results provide valuable insights for predicting taxi demand as a function of spatially explicit variables which may have implications on taxi pricing, taxi industry regulation and urban planning. }
}
@article{Zhu2015,
title = {A junction-tree based learning algorithm to optimize network wide traffic control: A coordinated multi-agent framework },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {},
number = {0},
pages = { - },
year = {2015},
note = {},
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/j.trc.2014.12.009},
url = {http://www.sciencedirect.com/science/article/pii/S0968090X14003593},
author = {Feng Zhu and H.M. Abdul Aziz and Xinwu Qian and Satish V. Ukkusuri},
keywords = {Reinforcement learning},
keywords = {Junction tree},
keywords = {Signal control coordination},
keywords = {\{VISSIM\}},
keywords = {Emissions},
keywords = {\{MOVES\} },
abstract = {Abstract This study develops a novel reinforcement learning algorithm for the challenging coordinated signal control problem. Traffic signals are modeled as intelligent agents interacting with the stochastic traffic environment. The model is built on the framework of coordinated reinforcement learning. The Junction Tree Algorithm (JTA) based reinforcement learning is proposed to obtain an exact inference of the best joint actions for all the coordinated intersections. The algorithm is implemented and tested with a network containing 18 signalized intersections in VISSIM. Results show that the \{JTA\} based algorithm outperforms independent learning (Q-learning), real-time adaptive learning, and fixed timing plans in terms of average delay, number of stops, and vehicular emissions at the network level. }
}
@article{Doan201541,
title = {Dynamic system optimal model for multi-OD traffic networks with an advanced spatial queuing model },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {51},
number = {0},
pages = {41 - 65},
year = {2015},
note = {},
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/j.trc.2014.10.011},
url = {http://www.sciencedirect.com/science/article/pii/S0968090X14003106},
author = {Kien Doan and Satish V Ukkusuri},
keywords = {System optimal},
keywords = {Cell transmission model},
keywords = {Path marginal cost},
keywords = {Projection algorithm },
abstract = {Abstract This paper provides an approach to solve the system optimal dynamic traffic assignment problem for networks with multiple O–D pairs. The path-based cell transmission model is embedded as the underlying dynamic network loading procedure to propagate traffic. We propose a novel method to fully capture the effect of flow perturbation on total system cost and accurately compute path marginal cost for each path. This path marginal cost pattern is used in the projection algorithm to equilibrate the departure rate pattern and solve the system optimal dynamic traffic assignment. We observe that the results from projection algorithm are more reliable than those from method of successive average algorithm (MSA). Several numerical experiments are tested to illustrate the benefits of the proposed model. }
}
@article{Aziz2014334,
title = {Exploring the trade-off between greenhouse gas emissions and travel time in daily travel decisions: Route and departure time choices },
journal = {Transportation Research Part D: Transport and Environment },
volume = {32},
number = {0},
pages = {334 - 353},
year = {2014},
note = {},
issn = {1361-9209},
doi = {http://dx.doi.org/10.1016/j.trd.2014.07.016},
url = {http://www.sciencedirect.com/science/article/pii/S1361920914001023},
author = {H.M. Abdul Aziz and Satish V. Ukkusuri},
keywords = {\{GHG\} emissions},
keywords = {Random parameter models},
keywords = {Green transportation},
keywords = {Trade-off},
keywords = {Emissions mitigation},
keywords = {Personal travel},
keywords = {Low carbon transport },
abstract = {Abstract This study analyzes the problem of conflicting travel time and emissions minimization in context of daily travel decisions. The conflict occurs because the least travel time option does not always lead to least emissions for the trip. Experiments are designed and conducted to collect data on daily trips. Random parameter (mixed) logit models accounting for correlations among repeated observations are estimated to find the trade-off between emissions and travel time. Our results show that the trade-off values vary with contexts such as route and departure time choice scenarios. Further, we find that the trade-off values are different for population groups representing male, female, individuals from high income households, and individuals who prefer bike for daily commute. Based on the findings, several policies are proposed that can help to lower greenhouse gas (GHG) emissions from transportation networks. This is one of the first exploratory studies that analyzes travel decisions and the corresponding trade-off when emissions related information are provided to the road users. }
}
@article{Sadri201437,
title = {Analysis of hurricane evacuee mode choice behavior },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {48},
number = {0},
pages = {37 - 46},
year = {2014},
note = {},
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/j.trc.2014.08.008},
url = {http://www.sciencedirect.com/science/article/pii/S0968090X14002241},
author = {Arif Mohaimin Sadri and Satish V. Ukkusuri and Pamela Murray-Tuite and Hugh Gladwin},
keywords = {Hurricane evacuation},
keywords = {Mode choice},
keywords = {Nested logit},
keywords = {Behavioral model},
keywords = {Evacuation modeling },
abstract = {Abstract The purpose of this study is to explain the evacuee mode choice behavior of Miami Beach residents using survey data from a hypothetical category four hurricane to reveal different evacuees’ plans. Evacuation logistics should incorporate the needs of transit users and car-less populations with special attention and proper treatment. A nested logit model has been developed to explain the mode choice decisions for evacuees’ from Miami Beach who use non-household transportation modes, such as special evacuation bus, taxi, regular bus, riding with someone from another household and another type of mode denoted and aggregated as other. Specifically, the model explains that the mode choice decisions of evacuees’, who are likely to use different non-household transportation modes, are influenced by several determining factors related to evacuees’ socio-demographics, household characteristics, evacuation destination and previous experience. The findings of this study will help emergency planners and policy-makers to develop better evacuation plans and strategies for evacuees depending on others for their evacuation transportation. }
}
@article{Zhu201430,
title = {Accounting for dynamic speed limit control in a stochastic traffic environment: A reinforcement learning approach },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {41},
number = {0},
pages = {30 - 47},
year = {2014},
note = {},
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/j.trc.2014.01.014},
url = {http://www.sciencedirect.com/science/article/pii/S0968090X1400028X},
author = {Feng Zhu and Satish V. Ukkusuri},
keywords = {Dynamic speed limit control},
keywords = {Stochastic network},
keywords = {Connected vehicle},
keywords = {Reinforcement learning},
keywords = {Network loading },
abstract = {Abstract This paper proposes a novel dynamic speed limit control model accounting for uncertain traffic demand and supply in a stochastic traffic network. First, a link based dynamic network loading model is developed to simulate the traffic flow propagation allowing the change of speed limits. Shockwave propagation is well defined and captured by checking the difference between the queue forming end and the dissipation end. Second, the dynamic speed limit problem is formulated as a Markov Decision Process (MDP) problem and solved by a real time control mechanism. The speed limit controller is modeled as an intelligent agent interacting with the stochastic network environment stochastic network environment to assign time dependent link based speed limits. Based on different metrics, e.g. total network throughput, delay time, vehicular emissions are optimized in the modeling framework, the optimal speed limit scheme is obtained by applying the R-Markov Average Reward Technique (R-MART) based reinforcement learning algorithm. A case study of the Sioux Falls network is constructed to test the performance of the model. Results show that the total travel time and emissions (in terms of CO) are reduced by around 18% and 20% compared with the base case of non-speed limit control. }
}
@article{MesaArango2014142,
title = {Attributes driving the selection of trucking services and the quantification of the shipper’s willingness to pay },
journal = {Transportation Research Part E: Logistics and Transportation Review },
volume = {71},
number = {0},
pages = {142 - 158},
year = {2014},
note = {},
issn = {1366-5545},
doi = {http://dx.doi.org/10.1016/j.tre.2014.09.004},
url = {http://www.sciencedirect.com/science/article/pii/S1366554514001586},
author = {Rodrigo Mesa-Arango and Satish V. Ukkusuri},
keywords = {Trucking},
keywords = {Freight},
keywords = {Discrete choice},
keywords = {Stated preferences},
keywords = {Willingness to pay},
keywords = {Revenue management },
abstract = {Abstract This paper investigates the selection of trucking services by shippers that require the movement of truck shipments. A set of pragmatic attributes are postulated to describe trucking services. They are used in a stated choice experiment that collects data and preferences from shippers. A mixed logit model is estimated in order to test the attributes and quantifying the shipper willingness to pay for them. The results are used to provide meaningful negotiation guidance for truck-related shippers and carriers, a significant contribution to literature in transportation, logistics, and supply chain management. A numerical example illustrates the use of the model. }
}
@article{Hasan2014363,
title = {Urban activity pattern classification using topic models from online geo-location data },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {44},
number = {0},
pages = {363 - 381},
year = {2014},
note = {},
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/j.trc.2014.04.003},
url = {http://www.sciencedirect.com/science/article/pii/S0968090X14000928},
author = {Samiul Hasan and Satish V. Ukkusuri},
keywords = {Activity pattern classification},
keywords = {Activity-based modeling},
keywords = {Social computing},
keywords = {Location-based data},
keywords = {Big data},
keywords = {Social media},
keywords = {Topic modeling},
keywords = {Machine learning },
abstract = {Abstract Location-based check-in services in various social media applications have enabled individuals to share their activity-related choices providing a new source of human activity data. Although geo-location data has the potential to infer multi-day patterns of individual activities, appropriate methodological approaches are needed. This paper presents a technique to analyze large-scale geo-location data from social media to infer individual activity patterns. A data-driven modeling approach, based on topic modeling, is proposed to classify patterns in individual activity choices. The model provides an activity generation mechanism which when combined with the data from traditional surveys is potentially a useful component of an activity-travel simulator. Using the model, aggregate patterns of users’ weekly activities are extracted from the data. The model is extended to also find user-specific activity patterns. We extend the model to account for missing activities (a major limitation of social media data) and demonstrate how information from activity-based diaries can be complemented with longitudinal geo-location information. This work provides foundational tools that can be used when geo-location data is available to predict disaggregate activity patterns. }
}
@article{Yin201444,
title = {An agent-based modeling system for travel demand simulation for hurricane evacuation },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {42},
number = {0},
pages = {44 - 59},
year = {2014},
note = {},
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/j.trc.2014.02.015},
url = {http://www.sciencedirect.com/science/article/pii/S0968090X14000576},
author = {Weihao Yin and Pamela Murray-Tuite and Satish V. Ukkusuri and Hugh Gladwin},
keywords = {Agent-based simulation},
keywords = {Travel demand},
keywords = {Hurricane evacuation },
abstract = {Abstract This paper presents an agent-based travel demand model system for hurricane evacuation simulation, which is capable of generating comprehensive household activity-travel plans. The system implements econometric and statistical models that represent travel and decision-making behavior throughout the evacuation process. The system considers six typical evacuation decisions: evacuate/stay, accommodation type choice, evacuation destination choice, mode choice, vehicle usage choice, and departure time choice. It explicitly captures the shadow evacuation population. In addition, the model system captures pre-evacuation preparation activities using an activity-based approach. A demonstration study that predicts activity-travel patterns using model parameters estimated for the Miami-Dade area for a hypothetical category-4 hurricane is discussed. The simulation results clearly indicate the model system produces a distribution of choice patterns that is consistent with sample observations and existing literature. The model system also identifies the proportion of the shadow evacuation population and their geographical extent. About 23% of the population outside the designated evacuation zone would evacuate. The shadow evacuation demand is mainly located within 5 km of the coastline. The output demand of the model system works with agent-based traffic simulation tools and conventional trip-based simulation tools. }
}
@article{Ukkusuri2013729,
title = {A Bi-level Formulation for the Combined Dynamic Equilibrium based Traffic Signal Control },
journal = {Procedia - Social and Behavioral Sciences },
volume = {80},
number = {0},
pages = {729 - 752},
year = {2013},
note = {20th International Symposium on Transportation and Traffic Theory (ISTTT 2013) },
issn = {1877-0428},
doi = {http://dx.doi.org/10.1016/j.sbspro.2013.05.039},
url = {http://www.sciencedirect.com/science/article/pii/S1877042813010082},
author = {Satish Ukkusuri and Kien Doan and H.M. Abdul Aziz},
keywords = {Dynamic user equilibrium},
keywords = {Signal control optimization},
keywords = {Nash-Cournot game},
keywords = {Stackelberg game},
keywords = {Mixed integer program},
keywords = {Projection algorithm },
abstract = {This paper formulates the combined dynamic user equilibrium and signal control problem (DUESC) as a bi-level optimization problem. The signal control operator in the upper level optimizes the signal setting to minimize the system travel time whereas the road users in the lower level minimize their own costs (by changing departure times, paths or both) leading to dynamic user equilibrium behavior. Three components of the bi-level formulation are discussed including network loading model, the dynamic user equilibrium model and the signal control model. Then the combined problems are formulated as a Nash-Cournot game and a Stackelberg game. A solution technique based on the iterative optimization and assignment (IOA) method is proposed to solve the \{DUESC\} problem. We use the projection algorithm to solve the lower level and the mixed integer programming solver to solve the upper level. Extensive numerical results demonstrate the benefits of using this model. }
}
@article{Mohamed201327,
title = {A clustering regression approach: A comprehensive injury severity analysis of pedestrian–vehicle crashes in New York, \{US\} and Montreal, Canada },
journal = {Safety Science },
volume = {54},
number = {0},
pages = {27 - 37},
year = {2013},
note = {},
issn = {0925-7535},
doi = {http://dx.doi.org/10.1016/j.ssci.2012.11.001},
url = {http://www.sciencedirect.com/science/article/pii/S0925753512002664},
author = {Mohamed Gomaa Mohamed and Nicolas Saunier and Luis F. Miranda-Moreno and Satish V. Ukkusuri},
keywords = {Pedestrian safety},
keywords = {Contributing factors},
keywords = {Latent class},
keywords = {Clustering injury severity},
keywords = {Pedestrian–driver characteristics},
keywords = {Built environmental },
abstract = {Understanding the underlying relationship between pedestrian injury severity outcomes and factors leading to more severe injuries is very important in addressing the problem of pedestrian safety. This research combines data mining and statistical regression methods to identify the main factors associated with the levels of pedestrian injury severity outcomes. This work relies on the analysis of two unique pedestrian injury severity datasets from New York City, \{US\} (2002–2006) and the City of Montreal, Canada (2003–2006). General injury severity models were estimated for each dataset and for sub-populations obtained through clustering analysis. This paper shows how the segmentation of the accident datasets helps to better understand the complex relationship between the injury severity outcomes and the contribution of geometric, built environment and socio-demographic factors. While using the same methodology for the two datasets, different techniques were tested. Within the New York dataset, a latent class with ordered probit method provides the best results. However, for Montreal, K-means with a multinomial logit model proves most appropriate. Among other results, it was found that pedestrian age, location type, driver age, vehicle type, driver alcohol involvement, lighting conditions, and several built environment characteristics influence the likelihood of fatal crashes. Finally, the research provides recommendations for policy makers, traffic engineers, and law enforcement in order to reduce the severity of pedestrian–vehicle collisions. }
}
@article{Zhu2013367,
title = {A cell based dynamic system optimum model with non-holding back flows },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {36},
number = {0},
pages = {367 - 380},
year = {2013},
note = {},
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/j.trc.2013.09.003},
url = {http://www.sciencedirect.com/science/article/pii/S0968090X13001836},
author = {Feng Zhu and Satish V. Ukkusuri},
keywords = {Cell transmission model},
keywords = {Linear programming},
keywords = {System optimal},
keywords = {Holding-back },
abstract = {Abstract This paper proposes a non-holding back linear programming (NHBLP) model with an embedded cell transmission model (CTM), to account for the system optimum dynamic traffic assignment. }
}
@article{Sadri201321,
title = {A random parameter ordered probit model to understand the mobilization time during hurricane evacuation },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {32},
number = {0},
pages = {21 - 30},
year = {2013},
note = {},
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/j.trc.2013.03.009},
url = {http://www.sciencedirect.com/science/article/pii/S0968090X13000727},
author = {Arif Mohaimin Sadri and Satish V. Ukkusuri and Pamela Murray-Tuite},
keywords = {Hurricane evacuation},
keywords = {Mobilization time},
keywords = {Ordered probit model},
keywords = {Random parameter model},
keywords = {Behavioral model},
keywords = {Hurricane Ivan },
abstract = {Abstract This paper presents a random parameters ordered probit model to capture underlying unobserved characteristics in the timing behavior of the evacuees that elapses in between their evacuation decision and actual evacuation i.e. the mobilization time for an evacuee. The ordered probit model has been developed by using Hurricane Ivan data and the estimation findings suggest that the mobilization time involves a complex interaction of variables related to household location, evacuation characteristics, and socio-economic characteristics among others. In the model, six variables- source and time of evacuation notice received, work constraint, previous hurricane experience, race and income- were found to be random and the random parameters (all normally distributed) suggest that their effect varies across the observations. In addition, the model introduces some new factors that impact the mobilization time (for example, the mobilization time for evacuees evacuating to public shelters is significantly lower) which have not been found in the earlier literature to the best of our knowledge. The findings of this study are useful to determine different fractions of people evacuating early or delaying for some time once they actually decide to evacuate, for a given socio-demographic profile. These fractions can be used in the future to develop more accurate dynamic travel demands for use in traffic simulation models. }
}
@article{MesaArango2013113,
title = {Benefits of in-vehicle consolidation in less than truckload freight transportation operations },
journal = {Transportation Research Part E: Logistics and Transportation Review },
volume = {60},
number = {0},
pages = {113 - 125},
year = {2013},
note = {},
issn = {1366-5545},
doi = {http://dx.doi.org/10.1016/j.tre.2013.05.007},
url = {http://www.sciencedirect.com/science/article/pii/S1366554513001208},
author = {Rodrigo Mesa-Arango and Satish V. Ukkusuri},
keywords = {Combinatorial auctions},
keywords = {Trucking},
keywords = {Less-Than-Truckload},
keywords = {Logistics},
keywords = {Branch-and-price},
keywords = {Consolidation},
keywords = {Vehicle routing problem},
keywords = {Multi-commodity one-to-one pickup-and-delivery },
abstract = {Abstract Researchers and public agencies have proposed consolidation policies as an alternative to increase truck payload utilization and mitigate externalities produced by freight transportation. Understanding and enhancing the economic mechanisms that lead to freight consolidation can ease the implementation of these strategies, increase profits for shippers and carriers, and reduce freight-related negative externalities. An important mechanism that has recently been studied for cost reduction in the freight industry is combinatorial auctions. In these auctions, a shipper invites a set of carriers to submit bids for freight lane contracts. Carriers can bid for individual lanes or bundles of them according to their operational characteristics. These bids are constructed considering direct shipments (Truckload operations) and several biding advisory models have been proposed for this purpose. However, there are economies of scale that can be achieved if shipments are consolidated inside vehicles, which have not been explored in the construction of competitive bids. This paper investigates such benefits and provides insights on the competitiveness and challenges associated to the development of consolidated bids (suitable for Less-Than-Truckload operations). Consolidated bids are constructed using a multi-commodity one-to-one pickup-and-delivery vehicle routing problem that is solved using a branch-and-price algorithm. The numerical experiment shows that non-consolidated bids are dominated by consolidated bids, which implies that this type of operation can increase the likelihood of a carrier to win auctioned lanes, while increasing its profits margins over truckload companies (non-consolidated bids), and keeping the reported benefits that combinatorial auctions represent for shippers. }
}
@article{MesaArango2013576,
title = {Benefits of in-Vehicle Consolidation in Less than Truckload Freight Transportation Operations },
journal = {Procedia - Social and Behavioral Sciences },
volume = {80},
number = {0},
pages = {576 - 590},
year = {2013},
note = {20th International Symposium on Transportation and Traffic Theory (ISTTT 2013) },
issn = {1877-0428},
doi = {http://dx.doi.org/10.1016/j.sbspro.2013.05.031},
url = {http://www.sciencedirect.com/science/article/pii/S1877042813010008},
author = {Rodrigo Mesa-Arango and Satish V. Ukkusuri},
keywords = {Freight transportation},
keywords = {combinatorial auctions},
keywords = {trucking},
keywords = {less than truckload},
keywords = {logistics},
keywords = {branch-and-price},
keywords = {consolidation},
keywords = {vehicle routing problem},
keywords = {multi-commodity},
keywords = {pickup and delivery },
abstract = {Abstract Researchers and public agencies have proposed consolidation policies as an alternative to increase truck payload utilization and mitigate externalities produced by freight transportation. Understanding and enhancing the economic mechanisms that lead to freight consolidation can ease the implementation of these strategies, increase profits for shippers and carriers, and reduce freight-related negative externalities. An important mechanism that has recently been studied for cost reduction in the freight industry is combinatorial auctions. In these auctions, a shipper invites a set of carriers to submit bids for freight lane contracts. Carriers can bid for individual lanes or bundles of them according to their operational characteristics. These bids are constructed considering direct shipments (Truckload operations) and several biding advisory models have been proposed for this purpose. However, there are economies of scale that can be achieved if shipments are consolidated inside vehicles, which have not been explored in the construction of competitive bids. This paper investigates such benefits and provides insights on the competitiveness and challenges associated to the development of consolidated bids (suitable for Less-than-Truckload operations). Consolidated bids are constructed using a multi-commodity one-to-one pickup-and-delivery vehicle routing problem that is solved using a branch-and-price algorithm. The numerical experiment shows that non-consolidated bids are dominated by consolidated bids, which implies that this type of operation can increase the likelihood of a carrier to win auctioned lanes, while increasing its profits margins over truckload companies (non-consolidated bids), and keeping the reported benefits that combinatorial auctions represent for shippers. }
}
@article{Zhan201337,
title = {Urban link travel time estimation using large-scale taxi data with partial information },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {33},
number = {0},
pages = {37 - 49},
year = {2013},
note = {},
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/j.trc.2013.04.001},
url = {http://www.sciencedirect.com/science/article/pii/S0968090X13000740},
author = {Xianyuan Zhan and Samiul Hasan and Satish V. Ukkusuri and Camille Kamga},
keywords = {Traffic state estimation},
keywords = {Path inference},
keywords = {Large scale data analysis},
keywords = {GPS-enabled taxicab},
keywords = {Probe vehicle},
keywords = {Urban networks },
abstract = {Abstract Taxicabs equipped with Global Positioning System (GPS) devices can serve as useful probes for monitoring the traffic state in an urban area. This paper presents a new descriptive model for estimating hourly average of urban link travel times using taxicab origin–destination (OD) trip data. The focus of this study is to develop a methodology to estimate link travel times from \{OD\} trip data and demonstrate the feasibility of estimating network condition using large-scale geo-location data with partial information. The data, collected from the taxicabs in New York City, provides the locations of origins and destinations, travel times, fares and other information of taxi trips. The new model infers the possible paths for each trip and then estimates the link travel times by minimizing the error between the expected path travel times and the observed path travel times. The model is evaluated using a test network from Midtown Manhattan. Results indicate that the proposed method can efficiently estimate hourly average link travel times. This research provides new possibilities for fully utilizing the partial information obtained from urban taxicab data for estimating network condition, which is not only very useful but also is inexpensive and has much better coverage than traditional sensor data. }
}
@article{Doan20121218,
title = {On the holding-back problem in the cell transmission based dynamic traffic assignment models },
journal = {Transportation Research Part B: Methodological },
volume = {46},
number = {9},
pages = {1218 - 1238},
year = {2012},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/j.trb.2012.05.001},
url = {http://www.sciencedirect.com/science/article/pii/S0191261512000732},
author = {Kien Doan and Satish V. Ukkusuri},
keywords = {Dynamic traffic assignment},
keywords = {System optimal},
keywords = {Cell transmission model},
keywords = {Holding-back},
keywords = {Network modeling },
abstract = {Traffic holding-back is considered an undesirable issue in dynamic traffic assignment since the vehicles are artificially held back on links in spite of the availability of downstream capacity. Holding-back occurs naturally in some system optimal dynamic traffic assignment models. In this paper, we focus on the holding back issue in the cell transmission based models and review the current methods of solving holding-back to understand their advantages and drawbacks. Then, we propose improvements to overcome the drawbacks of the current models. Finally, we propose a novel model which completely eliminates holding-back in a system optimal dynamic traffic assignment for traffic networks with multiple O–D pairs. Rigorous numerical results illustrate the benefits of using the proposed models. }
}
@article{Han20111749,
title = {Complementarity formulations for the cell transmission model based dynamic user equilibrium with departure time choice, elastic demand and user heterogeneity },
journal = {Transportation Research Part B: Methodological },
volume = {45},
number = {10},
pages = {1749 - 1767},
year = {2011},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/j.trb.2011.07.007},
url = {http://www.sciencedirect.com/science/article/pii/S019126151100107X},
author = {Lanshan Han and Satish Ukkusuri and Kien Doan},
keywords = {User equilibrium},
keywords = {Cell transmission model},
keywords = {Complementarity},
keywords = {Departure time},
keywords = {Heterogeneous users},
keywords = {Demand elasticity },
abstract = {In this paper we formulate the dynamic user equilibrium problem with an embedded cell transmission model on a network with a single \{OD\} pair, multiple parallel paths, multiple user classes with elastic demand. The formulation is based on ideas from complementarity theory. The travel time is estimated based on two methods which have different transportation applications: (1) maximum travel time and (2) average travel time. These travel time functions result in linear and non-linear complementarity formulations respectively. Solution existence and the properties of the formulations are rigorously analyzed. Extensive computational experiments are conducted to demonstrate the benefits of the proposed formulations on various test networks. }
}
@article{Doan2011269,
title = {On the existence of pricing strategies in the discrete time heterogeneous single bottleneck model },
journal = {Procedia - Social and Behavioral Sciences },
volume = {17},
number = {0},
pages = {269 - 291},
year = {2011},
note = {Papers selected for the 19th International Symposium on Transportation and Traffic Theory },
issn = {1877-0428},
doi = {http://dx.doi.org/10.1016/j.sbspro.2011.04.518},
url = {http://www.sciencedirect.com/science/article/pii/S1877042811010779},
author = {Kien Doan and Satish Ukkusuri and Lanshan Han},
keywords = {Single bottleneck},
keywords = {user equilibrium},
keywords = {system optimal},
keywords = {toll stratergies},
keywords = {heterogeneous commuter },
abstract = {In this paper, we study the pricing strategies in the discrete time single bottleneck model with general heterogeneous commuters. We first prove that in the system optimal assignment, the queue time must be zero for all the departures. Based on this result, the system optimal problem is formulated as a linear program. The solution existence and uniqueness are discussed. Applying linear programming duality, we then prove that the optimal dual variable values provide an optimal toll with which the system optimal solution is also an equilibrium solution. Extensive computational results are reported to demonstrate the insights gained from the formulations presented in this paper. These results confirm that a system optimal equilibrium can be found using the proposed approach. }
}
@article{Doan20111483,
title = {On the existence of pricing strategies in the discrete time heterogeneous single bottleneck model },
journal = {Transportation Research Part B: Methodological },
volume = {45},
number = {9},
pages = {1483 - 1500},
year = {2011},
note = {Select Papers from the 19th \{ISTTT\} },
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/j.trb.2011.05.019},
url = {http://www.sciencedirect.com/science/article/pii/S0191261511000695},
author = {Kien Doan and Satish Ukkusuri and Lanshan Han},
keywords = {Single bottleneck},
keywords = {User equilibrium},
keywords = {System optimal},
keywords = {Toll strategies},
keywords = {Heterogeneous commuter },
abstract = {In this paper, we study the pricing strategies in the discrete time single bottleneck model with general heterogeneous commuters. We first prove that in the system optimal assignment, the queue time must be zero for all the departures. Based on this result, the system optimal problem is formulated as a linear program. The solution existence and uniqueness are discussed. Applying linear programming duality, we then prove that the optimal dual variable values provide an optimal toll with which the system optimal solution is also an equilibrium solution. Extensive computational results are reported to demonstrate the insights gained from the formulations in this paper. These results confirm that a system optimal equilibrium can be found using the proposed approach. }
}
@article{Hasan2013108,
title = {A random-parameter hazard-based model to understand household evacuation timing behavior },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {27},
number = {0},
pages = {108 - 116},
year = {2013},
note = {Selected papers from the Seventh Triennial Symposium on Transportation Analysis (TRISTAN VII) },
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/j.trc.2011.06.005},
url = {http://www.sciencedirect.com/science/article/pii/S0968090X11000957},
author = {Samiul Hasan and Rodrigo Mesa-Arango and Satish Ukkusuri},
keywords = {Hurricane evacuation timing},
keywords = {Hazard-based model},
keywords = {Random-parameter model},
keywords = {Hurricane evacuation behavior},
keywords = {Hurricane Ivan },
abstract = {The goal of this paper is to develop a random-parameter hazard-based model to understand hurricane evacuation timing by individual households. The choice of departure time during disasters is a complex dynamic process and depends on the risk that the hazard represents, the characteristics of the household and the built environment features. However, the risk responses are heterogeneous across the households; this unobserved heterogeneity is captured through random parameters in the model. The model is estimated with data from Hurricane Ivan including households from Alabama, Louisiana, Florida and Mississippi. It is found that the variables related to household location, destination characteristics, socio-economic characteristics, evacuation notice and household decision making are key determinants of the departure time. As such the developed model provides some fundamental inferences about hurricane evacuation timing behavior. }
}
@article{Ukkusuri20121141,
title = {The role of built environment on pedestrian crash frequency },
journal = {Safety Science },
volume = {50},
number = {4},
pages = {1141 - 1151},
year = {2012},
note = {First International Symposium on Mine Safety Science and Engineering 2011 },
issn = {0925-7535},
doi = {http://dx.doi.org/10.1016/j.ssci.2011.09.012},
url = {http://www.sciencedirect.com/science/article/pii/S0925753511002578},
author = {Satish Ukkusuri and Luis F. Miranda-Moreno and Gitakrishnan Ramadurai and Jhael Isa-Tavarez},
keywords = {Built environment},
keywords = {Road geometry},
keywords = {Pedestrian crash occurrence},
keywords = {Spatial aggregation },
abstract = {This study investigates (i) the link of land use and road design on pedestrian safety and (ii) the effect of the level of spatial aggregation on the frequency of pedestrian accidents. For this purpose, pedestrian accident frequency models were developed for New York City based on an extensive dataset collected from different sources over a period of 5 years. The assembled dataset provides a rich source of variables (land-use, demographics, transit supply, road network and travel characteristics) and two different crash frequency outcomes: total and fatal-only collision counts. Among other things, it was observed that the census tract analysis (disaggregate data) provides more insightful and consistent results than the analysis at the zip code level. The results indicate that tracts with greater fraction of industrial, commercial, and open land use types have greater likelihood for crashes while tracts with a greater fraction of residential land use have significantly lower likelihood of pedestrian crashes. Moreover, census tracts that have a greater number of schools and transit stops – which are determinants of pedestrian activity – are more likely to have greater crashes. Results also show that the likelihood of pedestrian–vehicle collision increases with the number of lanes and road width. This suggests that retrofitting or narrowing the roads could possibly reduce the risk of pedestrian crashes. }
}
@article{Aziz20131298,
title = {Exploring the determinants of pedestrian–vehicle crash severity in New York City },
journal = {Accident Analysis & Prevention },
volume = {50},
number = {0},
pages = {1298 - 1309},
year = {2013},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2012.09.034},
url = {http://www.sciencedirect.com/science/article/pii/S0001457512003533},
author = {H.M. Abdul Aziz and Satish V. Ukkusuri and Samiul Hasan},
keywords = {Pedestrian–vehicle crashes},
keywords = {Severity modeling},
keywords = {Random parameter model},
keywords = {New York City},
keywords = {Built environment },
abstract = {Pedestrian–vehicle crashes remain a major concern in New York City due to high percentage of fatalities. This study develops random parameter logit models for explaining pedestrian injury severity levels of New York City accounting for unobserved heterogeneity in the population and across the boroughs. A log-likelihood ratio test for joint model suitability suggests that separate models for each of the boroughs should be estimated. Among many variables, road characteristics (e.g., number of lanes, grade, light condition, road surface, etc.), traffic attributes (e.g., presence of signal control, type of vehicle, etc.), and land use (e.g., parking facilities, commercial and industrial land use, etc.) are found to be statistically significant in the estimated model. The study also suggests that the set of counter measures should be different for different boroughs in the New York City and the priority ranks of countermeasures should be different as well. }
}
@article{Hasan20111590,
title = {A threshold model of social contagion process for evacuation decision making },
journal = {Transportation Research Part B: Methodological },
volume = {45},
number = {10},
pages = {1590 - 1605},
year = {2011},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/j.trb.2011.07.008},
url = {http://www.sciencedirect.com/science/article/pii/S0191261511001081},
author = {Samiul Hasan and Satish V. Ukkusuri},
keywords = {Network science},
keywords = {Evacuation decision making},
keywords = {Warning propagation},
keywords = {Complex networks},
keywords = {Contagion model },
abstract = {Individual evacuation decisions are often characterized by the influence of one’s social network. In this paper a threshold model of social contagion, originally proposed in the network science literature, is presented to characterize this social influence in the evacuation decision making process. Initiated by a single agent, the condition of a cascade when a portion of the population decides to evacuate has been derived from the model. Simulation models are also developed to investigate the effects of community mixing patterns and the initial seed on cascade propagation and the effect of previous time-steps considered by the agents and the strength of ties on average cascade size. Insights related to social influence include the significant role of mixing patterns among communities in the network and the role of the initial seed on cascade propagation. Specifically, faster propagation of warning is observed in community networks with greater inter-community connections. }
}
@article{Ukkusuri2009625,
title = {Multi-period transportation network design under demand uncertainty },
journal = {Transportation Research Part B: Methodological },
volume = {43},
number = {6},
pages = {625 - 642},
year = {2009},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/j.trb.2009.01.004},
url = {http://www.sciencedirect.com/science/article/pii/S0191261509000150},
author = {Satish V. Ukkusuri and Gopal Patil},
keywords = {Network design},
keywords = {Equilibrium},
keywords = {Flexibility},
keywords = {Stochasticity},
keywords = {Mathematical program with equilibrium constraints (MPEC) },
abstract = {The ability to make optimal transportation network investments decision is central to the strategic management of transportation systems. The presence of uncertainty in transportation systems presents new challenges in making optimal network investment decisions. In this paper, we develop a multi time period network design problem considering both demand uncertainty and demand elasticity. Such an approach affords the planner the flexibility to delay, change, or even abandon the future network investment. We measure the flexibility of investing over multiple time periods as compared to a single-stage network design decision. Initially, we provide a taxonomy and define many dimensions of transportation network flexibility. This is followed with the development of a flexible network design formulation (FNDP), in which the investment is staged over multiple time periods. The demand is assumed to be separable and the demand elasticity is captured using a negative exponential distribution. We develop the \{FNDP\} formulation as bilevel stochastic mathematical programming with complementarity constraints (STOCH-MPEC) in which the bi-level formulation is converted to a single level using non-linear complementarity constraints conditions for user equilibrium (UE) problem. The formulation is implemented on two test networks and the results show the benefits of \{FNDP\} over single-stage NDP—measured in terms of increase in present expected system consumer surplus (PESCS)—are in the range of 10–30%. The results clearly demonstrate that under demand uncertainty there are potential benefits of introducing flexibility in investment decisions. Finally, we conduct a sensitivity analysis of \{FNDP\} with different budget values and it is observed that certain paradoxical sharp corners are observed at certain budget values. }
}
@article{Ukkusuri2008615,
title = {Geometric connectivity of vehicular ad hoc networks: Analytical characterization },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {16},
number = {5},
pages = {615 - 634},
year = {2008},
note = {},
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/j.trc.2007.12.002},
url = {http://www.sciencedirect.com/science/article/pii/S0968090X07000915},
author = {Satish Ukkusuri and Lili Du},
keywords = {\{VANET\} connectivitythe number of reachable neighbors},
keywords = {Information propagation},
keywords = {Vehicular ad hoc networks},
keywords = {Intelligent transportation systems},
keywords = {Connectivity},
keywords = {Reachable neighbors },
abstract = {Advances in wireless communications are facilitating the development of inter-vehicle communication systems that will benefit mobility and safety objectives. Recently, these systems, referred as vehicular ad hoc networks (VANETs), are gaining significant prominence from both government agencies and private organizations. \{VANETs\} are characterized by high vehicle mobility, unexpected driver behavior and variable traffic environment which bring forth challenges to maintain good connectivity. This study considers \{VANETs\} as a nominal system with disturbance. Under the nominal system, the traffic space headway is assumed to follow an approved traffic flow distributions, such as exponential distribution. Disturbance is then used to capture a set of uncertain traffic flow events caused by driver behavior and changes in traffic flow. In addition, robustness factor is incorporated to present the impact of probabilistic disturbance events that disrupt the node connectivity. Under constant disturbance conditions, the lower bound of reachable neighbors for each vehicle to maintain a high connectivity is analytically derived. Furthermore, we obtain the relationship between the number of nodes in a \{VANET\} and the reachable neighbors under which the network is asymptotically connected. Finally, in variable disturbance situations, the interaction between robustness factor and macroscopic traffic parameters are investigated based on the simulation data. The validation results demonstrate that the proposed analytical characterization can approximate \{VANET\} connectivity very well. Our results facilitate the understanding of \{VANET\} connectivity on a freeway segment under different traffic conditions. }
}
@article{Du2009571,
title = {Optimization models to characterize the broadcast capacity of vehicular ad hoc networks },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {17},
number = {6},
pages = {571 - 585},
year = {2009},
note = {},
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/j.trc.2008.07.003},
url = {http://www.sciencedirect.com/science/article/pii/S0968090X08000636},
author = {Lili Du and Satish Ukkusuri and Wilfredo F. Yushimito Del Valle and Shivkumar Kalyanaraman},
keywords = {Vehicular ad hoc networks},
keywords = {\{ATIS\}},
keywords = {Broadcast capacity},
keywords = {Information flow},
keywords = {Optimization},
keywords = {Integer program },
abstract = {Broadcast capacity of the entire network is one of the fundamental properties of vehicular ad hoc networks (VANETs). It measures how efficiently the information can be transmitted in the network and usually it is limited by the interference between the concurrent transmissions in the physical layer of the network. This study defines the broadcast capacity of vehicular ad hoc network as the maximum successful concurrent transmissions. In other words, we measure the maximum number of packets which can be transmitted in a \{VANET\} simultaneously, which characterizes how fast a new message such as a traffic incident can be transmitted in a VANET. Integer programming (IP) models are first developed to explore the maximum number of successful receiving nodes as well as the maximum number of transmitting nodes in a VANET. The models embed an traffic flow model in the optimization problem. Since \{IP\} model cannot be efficiently solved as the network size increases, this study develops a statistical model to predict the network capacity based on the significant parameters in the transportation and communication networks. \{MITSIMLab\} is used to generate the necessary traffic flow data. Response surface method and linear regression technologies are applied to build the statistical models. Thus, this paper brings together an array of tools to solve the broadcast capacity problem in VANETs. The proposed methodology provides an efficient approach to estimate the performance of a \{VANET\} in real-time, which will impact the efficacy of travel decision making. }
}
@article{Ukkusuri2010869,
title = {A robust transportation signal control problem accounting for traffic dynamics },
journal = {Computers & Operations Research },
volume = {37},
number = {5},
pages = {869 - 879},
year = {2010},
note = {Disruption Management },
issn = {0305-0548},
doi = {http://dx.doi.org/10.1016/j.cor.2009.03.017},
url = {http://www.sciencedirect.com/science/article/pii/S030505480900094X},
author = {Satish V. Ukkusuri and Gitakrishnan Ramadurai and Gopal Patil},
keywords = {Robust optimization},
keywords = {Dynamic traffic assignment},
keywords = {Signal control},
keywords = {Cell transmission model },
abstract = {Transportation system analysis must rely on predictions of the future that, by their very nature, contain substantial uncertainty. Future demand, demographics, and network capacities are only a few of the parameters that must be accounted for in both the planning and every day operations of transportation networks. While many repercussions of uncertainty exist, a primary concern in traffic operations is to develop efficient traffic signal designs that satisfy certain measures of short term future system performance while accounting for the different possible realizations of traffic state. As a result,uncertainty has to be incorporated in the design of traffic signal systems. Current dynamic traffic equilibrium models accounting for signal design, however, are not suitable for quantifying network performance over the range of possible scenarios and in analyzing the robust performance of the system. The purpose of this paper is to propose a new approach—robust system optimal signal control model; a supply-side within day operational transportation model where future transportation demand is assumed to be uncertain. A robust dynamic system optimal model with an embedded cell transmission model is formulated. Numerical analysis are performed on a test network to illustrate the benefits of accounting for uncertainty and robustness. }
}
@article{Ramadurai2010193,
title = {Linear complementarity formulation for single bottleneck model with heterogeneous commuters },
journal = {Transportation Research Part B: Methodological },
volume = {44},
number = {2},
pages = {193 - 214},
year = {2010},
note = {},
issn = {0191-2615},
doi = {http://dx.doi.org/10.1016/j.trb.2009.07.005},
url = {http://www.sciencedirect.com/science/article/pii/S0191261509000848},
author = {Gitakrishnan Ramadurai and Satish V. Ukkusuri and Jinye Zhao and Jong-Shi Pang},
keywords = {Single bottleneck model},
keywords = {Dynamic traffic equilibrium},
keywords = {Complementarity formulation},
keywords = {Heterogeneous commuters},
keywords = {Uniqueness },
abstract = {This paper formulates the dynamic equilibrium conditions for a single bottleneck model with heterogeneous commuters as a linear complementarity problem. This novel formulation offers a formal framework for the rigorous study and solution of a single bottleneck model with general heterogeneity parameter assumptions, enabling the adoption of well established complementarity theory and methods to analyze the model, and providing a significant contribution to the existing literature that either lacks a rigorous formulation or solves the problem under a limited set of heterogeneity parameter assumptions. The paper presents theoretical proofs for solution existence and uniqueness, and numerical results and insights for different heterogeneity assumptions. }
}
@article{Barkan20071266,
title = {Optimizing the design of railway tank cars to minimize accident-caused releases },
journal = {Computers & Operations Research },
volume = {34},
number = {5},
pages = {1266 - 1286},
year = {2007},
note = {Hazardous Materials Transportation },
issn = {0305-0548},
doi = {http://dx.doi.org/10.1016/j.cor.2005.06.002},
url = {http://www.sciencedirect.com/science/article/pii/S0305054805001814},
author = {Christopher P.L. Barkan and Satish V. Ukkusuri and S. Travis Waller},
abstract = {The design of vehicles transporting hazardous materials has important public safety and economic implications. Conventional wisdom among industry and government has held that a thicker tank on railroad tank cars and trucks reduces risk. However, a thicker tank increases vehicle weight and thus leads to an increase in the number of shipments required to transport the same amount of product and consequently greater exposure to accidents. In this research we develop a model that analyzes the tradeoff between increased damage resistance and greater exposure to accidents in which the objective function is minimization of the probability of release. The model accounts for the reduction in tank car release probability as a function of tank thickness, and the increased exposure to accidents that occurs due to the increased number of shipments needed for the heavier car. Three variables affecting this optimal thickness are considered in this paper: the volumetric capacity of the tank, the probability of release from other, non-tank sources, and the weight capacity of the car. Sensitivity analyses using the model indicate that for any particular configuration of tank car there is an optimal thickness. This optimal thickness is affected by several factors and there is no single optimum for all tank cars. }
}
@comment{{Andrew Tarko Papers}}
@article{Zou201455,
title = {Effectiveness of cable barriers, guardrails, and concrete barrier walls in reducing the risk of injury },
journal = {Accident Analysis & Prevention },
volume = {72},
number = {0},
pages = {55 - 65},
year = {2014},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2014.06.013},
url = {http://www.sciencedirect.com/science/article/pii/S0001457514001869},
author = {Yaotian Zou and Andrew P. Tarko and Erdong Chen and Mario A. Romero},
keywords = {Safety},
keywords = {Road barriers},
keywords = {Risk of injury},
keywords = {Probabilistic model},
keywords = {Random effects },
abstract = {Abstract Roadway departure crashes tend to be severe, especially when the roadside exposes the occupants of errant vehicles to excessive injury hazards. As a cost-effective method when the clear zone width is insufficient, road barriers are often installed to prevent errant vehicles from colliding with dangerous obstacles or traversing steep slopes. This paper focuses on the safety performance of road barriers in Indiana in reducing the risk of injury. The objective of the study presented here is to compare the risk of injury among different hazardous events faced by an occupant in a single-vehicle crash. The studied hazardous events include rolling over, striking three types of barriers (guardrails, concrete barrier walls, and cable barriers) with different barrier offsets to the edge of the travelled way, and striking various roadside objects. A total of 2124 single-vehicle crashes (3257 occupants) that occurred between 2008 and 2012 on 517 pair-matched homogeneous barrier and non-barrier segments were analyzed. A binary logistic regression model with mixed effects was estimated for vehicle occupants. The segment pairing process and the use of random effects were able to handle the commonality within the same segment pair as well as the heterogeneity across segment pairs. The modeling results revealed that hitting a barrier is associated with lower risk of injury than a high-hazard event (hitting a pole, rollover, etc.). The odds of injury are reduced by 39% for median concrete barrier walls offset 15–18 ft from the travelled way, reduced by 65% for a guardrail face offset 5–55 ft, reduced by 85% for near-side median cable barriers (offset between 10 ft and 29 ft), and reduced by 78% with far-side median cable barriers (offset at least 30 ft). Comparing different types of barriers is useful where some types of barriers can be used alternatively. This study found that the odds of injury are 43% lower when striking a guardrail instead of a median concrete barrier offset 15–18 ft and 65% lower when striking a median concrete barrier offset 7–14 ft. The odds of injury when striking a near-side median cable barrier is 57% lower than the odds for a guardrail face. This reduction for a far side median cable barrier is 37%. Thus, a guardrail should be preferred over a concrete wall and a cable barrier should be preferred over a guardrail where the road and traffic conditions allow. In the light of the results, installing median cable barriers on both sides of the median to reduce their lateral offset is beneficial for safety. The study also found that the unexplained heterogeneity across vehicles is much larger than it was across matched segment pairs. }
}
@article{Chen201486,
title = {Modeling safety of highway work zones with random parameters and random effects models },
journal = {Analytic Methods in Accident Research },
volume = {1},
number = {0},
pages = {86 - 95},
year = {2014},
note = {},
issn = {2213-6657},
doi = {http://dx.doi.org/10.1016/j.amar.2013.10.003},
url = {http://www.sciencedirect.com/science/article/pii/S2213665713000067},
author = {Erdong Chen and Andrew P. Tarko},
keywords = {Highway safety},
keywords = {Work zone safety},
keywords = {Crash frequency modeling},
keywords = {Random parameters},
keywords = {Negative binomial model },
abstract = {Abstract This paper presents an investigation of traffic safety in highway work zones using detailed data obtained from the results of a survey of project engineers and existing datasets. The observations were organized in monthly clusters that correspond to individual work zones; and a two-level random parameters negative binomial model that reflected the structure of the observations was estimated. The safety effects of various work zone design and traffic management features were identified, including lane shift, lane split, and detour, whose safety effects have not been evaluated in past research. This new insight into highway work zone safety was accomplished thanks to the better data acquired and the improved statistical model. A fixed parameters negative binomial model with random effects then was estimated to check its viability as an alternative to the random parameters model when the sample's large size makes estimation of the latter challenging. From a practical standpoint, the marginal effects on crash frequency computed from the model with random effects were quite similar to those computed from the random parameters model. This result indicates that, at least in some cases, convenient fixed parameters models may be a practical alternative to random parameters models. Utilization of an entire sample to estimate these conventional models may further compensate a less advanced model specification. The obtained negative binomial model with random effects has become useful for programming police enforcement in highway work zones in Indiana. }
}
@article{Xu201330,
title = {Predicting crash likelihood and severity on freeways with real-time loop detector data },
journal = {Accident Analysis & Prevention },
volume = {57},
number = {0},
pages = {30 - 39},
year = {2013},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2013.03.035},
url = {http://www.sciencedirect.com/science/article/pii/S0001457513001334},
author = {Chengcheng Xu and Andrew P. Tarko and Wei Wang and Pan Liu},
keywords = {Crash severity},
keywords = {Real-time safety management},
keywords = {Crash risk prediction},
keywords = {Sequential logit model},
keywords = {Freeway },
abstract = {Abstract Real-time crash risk prediction using traffic data collected from loop detector stations is useful in dynamic safety management systems aimed at improving traffic safety through application of proactive safety countermeasures. The major drawback of most of the existing studies is that they focus on the crash risk without consideration of crash severity. This paper presents an effort to develop a model that predicts the crash likelihood at different levels of severity with a particular focus on severe crashes. The crash data and traffic data used in this study were collected on the I-880 freeway in California, United States. This study considers three levels of crash severity: fatal/incapacitating injury crashes (KA), non-incapacitating/possible injury crashes (BC), and property-damage-only crashes (PDO). The sequential logit model was used to link the likelihood of crash occurrences at different severity levels to various traffic flow characteristics derived from detector data. The elasticity analysis was conducted to evaluate the effect of the traffic flow variables on the likelihood of crash and its severity.The results show that the traffic flow characteristics contributing to crash likelihood were quite different at different levels of severity. The \{PDO\} crashes were more likely to occur under congested traffic flow conditions with highly variable speed and frequent lane changes, while the \{KA\} and \{BC\} crashes were more likely to occur under less congested traffic flow conditions. High speed, coupled with a large speed difference between adjacent lanes under uncongested traffic conditions, was found to increase the likelihood of severe crashes (KA). This study applied the 20-fold cross-validation method to estimate the prediction performance of the developed models. The validation results show that the model's crash prediction performance at each severity level was satisfactory. The findings of this study can be used to predict the probabilities of crash at different severity levels, which is valuable knowledge in the pursuit of reducing the risk of severe crashes through the use of dynamic safety management systems on freeways. }
}
@article{Montella201249,
title = {Critical Review of the International Crash Databases and Proposals for Improvement of the Italian National Database },
journal = {Procedia - Social and Behavioral Sciences },
volume = {53},
number = {0},
pages = {49 - 61},
year = {2012},
note = {SIIV-5th International Congress - Sustainability of Road Infrastructures 2012 },
issn = {1877-0428},
doi = {http://dx.doi.org/10.1016/j.sbspro.2012.09.859},
url = {http://www.sciencedirect.com/science/article/pii/S1877042812043212},
author = {Alfonso Montella and David Andreassen and Andrew P. Tarko and Shane Turner and Filomena Mauriello and Lella Liana Imbriani and Mario A. Romero and Rohit Singh},
keywords = {Highway safety},
keywords = {Crash data},
keywords = {Injury severity},
keywords = {Crash contributory factors },
abstract = {Crash data collection is crucial for road safety improvement, but Italy is considerably behind the best international practices. To help to bridge this gap, a critical review of international crash databases was carried out and recommendations for improvement of the Italian police crash data collection and the national crash database were formulated.Main issues identified in the research are related to the database access procedures, the crash report, the crash location, the crash classification, and the severity classification. }
}
@article{Tarko2012230,
title = {Use of crash surrogates and exceedance statistics to estimate road safety },
journal = {Accident Analysis & Prevention },
volume = {45},
number = {0},
pages = {230 - 240},
year = {2012},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2011.07.008},
url = {http://www.sciencedirect.com/science/article/pii/S000145751100193X},
author = {Andrew P. Tarko},
keywords = {Safety modeling},
keywords = {Crash causality},
keywords = {Generalized Pareto distribution},
keywords = {Surrogate events},
keywords = {Continuum of traffic events},
keywords = {Traffic conflicts },
abstract = {The limited ability of existing safety models to properly reflect crash causality has its source in cross-sectional analysis applied to the estimation of the intrinsically complex safety factors with highly aggregated and frequently poor quality of data. The adequacy of the data may be improved thanks to the unprecedented progress in sensing technologies and the invention of the naturalistic driving method of data collection. Proposed in this paper is a new modeling paradigm that integrates several types of safety models. The primary improvement results from a more adequate representation of the crash occurrence process by incorporating crash precursor events into the modeling framework. A Pareto-based estimating method for the likelihood of a collision occurrence, given a precursor event, is explained and illustrated with the simple example of road departures. }
}
@article{Tarko2009608,
title = {Modeling drivers’ speed selection as a trade-off behavior },
journal = {Accident Analysis & Prevention },
volume = {41},
number = {3},
pages = {608 - 616},
year = {2009},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2009.02.008},
url = {http://www.sciencedirect.com/science/article/pii/S0001457509000438},
author = {Andrew P. Tarko},
keywords = {Preferred speed},
keywords = {Speed model},
keywords = {Trade-off behavior},
keywords = {Risk perception factors },
abstract = {This paper proposes a new model of driver-preferred speeds derived from the assumption that drivers trade-off a portion of their safety for a time gain. The risk of receiving a ticket for speeding is also considered. A trip disutility concept is selected to combine the three components of speed choice (safety, time, and enforcement). The perceived crash risk and speed enforcement are considered as speed deterrents while the perceived value of a time gain is considered as a speed enticement. According to this concept, speeds that minimize the perceived trip disutility are preferred by drivers. The modeled trade-off behavior does not have to be fully rational since it is affected by drivers’ preferences and their ability to perceive the risk. As such, the proposed framework follows the concept of bound rationality. The attractiveness of the model lies in its parameters being estimable with the observed preferred speeds and then interpretable as the factors of risk perception, the subjective value of time, and the perceived risk of speed enforcement. The proposed method may successfully supplement behavioral studies based on a driver survey. The study focuses on four-lane rural and suburban roads in Indiana, USA. The behavior of two types of drivers (trucks and cars) is modeled. The selection of test sites was such that the roads and other local characteristics varied across the studied sites while the population of drivers could be assumed as the same. The density of intersections, land development along the road, and the presence of sidewalks were the identified prominent risk perception factors. Another interesting finding is that the speed limit seems to encourage slow drivers to drive faster and fast drivers to drive slower. }
}
@article{Songchitruksa2006811,
title = {The extreme value theory approach to safety estimation },
journal = {Accident Analysis & Prevention },
volume = {38},
number = {4},
pages = {811 - 822},
year = {2006},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2006.02.003},
url = {http://www.sciencedirect.com/science/article/pii/S0001457506000236},
author = {Praprut Songchitruksa and Andrew P. Tarko},
keywords = {Extreme value theory},
keywords = {Traffic conflicts},
keywords = {Surrogate safety measures},
keywords = {Safety estimation},
keywords = {Safety modeling },
abstract = {Crash-based safety analysis is hampered by several shortcomings, such as randomness and rarity of crash occurrences, lack of timeliness, and inconsistency in crash reporting. Safety analysis based on observable traffic characteristics more frequent than crashes is one promising alternative. In this research, we proposed a novel application of the extreme value theory to estimate safety. The method is considered proactive in that it no longer requires historical crash data for the model calibration. We evaluated the proposed method by applying it to right-angle collisions at signalized intersections. Evaluation results indicated a promising relationship between safety estimates and historical crash data. Crash estimates at seven out of twelve sites remained within the range of Poisson-based confidence intervals established using historical crash data. The test has yielded large-variance safety estimates due to the short 8-h observation period. A simulation experiment conducted in this study revealed that 3–6 weeks of observation are needed to obtain safety estimates with confidence intervals comparable to those being obtained from 4-year observed crash counts. The proposed method can be applied to other types of locations and collisions as well. }
}
@article{Cerwick201411,
title = {A comparison of the mixed logit and latent class methods for crash severity analysis },
journal = {Analytic Methods in Accident Research },
volume = {3–4},
number = {0},
pages = {11 - 27},
year = {2014},
note = {},
issn = {2213-6657},
doi = {http://dx.doi.org/10.1016/j.amar.2014.09.002},
url = {http://www.sciencedirect.com/science/article/pii/S2213665714000244},
author = {Donald Mathew Cerwick and Konstantina Gkritza and Mohammad Saad Shaheed and Zachary Hans},
keywords = {Truck safety},
keywords = {Crash severity},
keywords = {Mixed logit method},
keywords = {Latent class method},
keywords = {Heterogeneity },
abstract = {Abstract While there have been many studies analyzing crash severity, few studies have accounted for unobserved heterogeneity and compared different crash severity models. The objective of this paper is to investigate the differences between two preferred methods for accommodating individual unobserved heterogeneity, the mixed logit and latent class methods, in exploring the relationship between heavy truck crash severity and its contributing factors. To achieve this, a large sample of crash data on multiple vehicle crashes involving a heavy truck on public roadways in Iowa from 2007 to 2012 was collected. The comparison of the two methods lied on model fit, inferences, and predicted crash severity outcome probabilities. The results suggested a slight superiority of the latent class method in terms of model fit; however, the mixed logit predicted probabilities for all three levels of injury severities were closer (on average) to the observations than the ones predicted by the latent class model. Only a few notable differences in the inferences were found between the two models. }
}
@article{Shaheed201430,
title = {A latent class analysis of single-vehicle motorcycle crash severity outcomes },
journal = {Analytic Methods in Accident Research },
volume = {2},
number = {0},
pages = {30 - 38},
year = {2014},
note = {},
issn = {2213-6657},
doi = {http://dx.doi.org/10.1016/j.amar.2014.03.002},
url = {http://www.sciencedirect.com/science/article/pii/S2213665714000190},
author = {Mohammad Saad Shaheed and Konstantina Gkritza},
keywords = {Crash severity},
keywords = {Heterogeneity},
keywords = {Latent class analysis},
keywords = {Motorcycle safety},
keywords = {Single-vehicle crashes },
abstract = {Abstract Unobserved heterogeneity has been recognized as a critical issue in traffic safety research that has not been completely addressed or often overlooked, and can lead to biased estimates and incorrect inferences if inappropriate methods are used. This paper uses a latent class approach to investigate the factors that affect crash severity outcomes in single-vehicle motorcycle crashes. Motorcycle crash data from 2001 to 2008 in Iowa were collected with a total of 3644 single-vehicle motorcycle crashes occurring during that time period. A latent class multinomial logit model is estimated that addresses unobserved heterogeneity by identifying two distinct crash data classes with homogeneous attributes. The estimation results show a significant relationship between severe crash injury outcomes and crash-specific factors (such as speeding, run-off road, collision with fixed object and overturn/rollover), riding on high-speed roads, riding on rural roads, riding on dry road surface, riding without a helmet, age (riders older than 25 years old) and impaired riding (riders under the influence of drug, alcohol or medication). The model fit and estimation results underline the need for segmentation of crashes, and suggest that the latent class approach can be a promising tool for modeling motorcycle crash severity outcomes. }
}
@article{Shaheed2013119,
title = {A mixed logit analysis of two-vehicle crash severities involving a motorcycle },
journal = {Accident Analysis & Prevention },
volume = {61},
number = {0},
pages = {119 - 128},
year = {2013},
note = {Emerging Research Methods and Their Application to Road Safety Emerging Issues in Safe and Sustainable Mobility for Older Persons The Candrive/Ozcandrive Prospective Older Driver Study: Methodology and Early Study Findings },
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2013.05.028},
url = {http://www.sciencedirect.com/science/article/pii/S0001457513002273},
author = {Mohammad Saad B. Shaheed and Konstantina Gkritza and Wei Zhang and Zachary Hans},
keywords = {Motorcycle safety},
keywords = {Crash severity},
keywords = {Mixed logit model},
keywords = {Conspicuity},
keywords = {Two-vehicle crashes },
abstract = {Abstract Using motorcycle crash data for Iowa from 2001 to 2008, this paper estimates a mixed logit model to investigate the factors that affect crash severity outcomes in a collision between a motorcycle and another vehicle. These include crash-specific factors (such as manner of collision, motorcycle rider and non-motorcycle driver and vehicle actions), roadway and environmental conditions, location and time, motorcycle rider and non-motorcycle driver and vehicle attributes. The methodological approach allows the parameters to vary across observations as opposed to a single parameter representing all observations. Our results showed non-uniform effects of rear-end collisions on minor injury crashes, as well as of the roadway speed limit greater or equal to 55 mph, the type of area (urban), the riding season (summer) and motorcyclist's gender on low severity crashes. We also found significant effects of the roadway surface condition, clear vision (not obscured by moving vehicles, trees, buildings, or other), light conditions, speed limit, and helmet use on severe injury outcomes. }
}
@comment{{Chiou Papers}}
@article{Chiou20141,
title = {Incorporating spatial dependence in simultaneously modeling crash frequency and severity },
journal = {Analytic Methods in Accident Research },
volume = {2},
number = {0},
pages = {1 - 11},
year = {2014},
note = {},
issn = {2213-6657},
doi = {http://dx.doi.org/10.1016/j.amar.2013.12.001},
url = {http://www.sciencedirect.com/science/article/pii/S2213665714000074},
author = {Yu-Chiun Chiou and Chiang Fu and Hsieh Chih-Wei},
keywords = {Spatial dependence},
keywords = {Multinomial-generalized Poisson with error-components},
keywords = {Spatial errors},
keywords = {Spatial exogenous function },
abstract = {Abstract Estimation results obtained by models of crash frequency and severity without considering spatial dependence effects may lead to biased estimates and mis-specification of the risk factors in accident analysis. The solution developed in this study is a modification of the previously proposed multinomial-generalized Poisson with error-components (EMGP) model. Two spatial \{EMGP\} models, spatial error-EMGP and spatial exogenous-EMGP, are proposed to accommodate alternative spatial dependence structures. The spatial error-EMGP model incorporates spatial error in the structure of spatial auto-regression and spatial moving average to capture spatial correlation effects; while the spatial exogenous-EMGP model introduces the spatial exogenous functions composed of two state parameterized functions associated with traffic and geometric composite variables to explain the sources of spatial dependence. A case study of crash data for Taiwan Freeway no. 1 is performed. According to the estimation results, the spatial exogenous-EMGP model not only performs best in terms of BIC, \{RMSE\} and \{LR\} tests, it also shows the sources of spatial dependence and how spatial dependence decays as the distance to adjacent segments increases. }
}
@article{Lan20102077,
title = {Cellular automaton simulations for mixed traffic with erratic motorcycles’ behaviours },
journal = {Physica A: Statistical Mechanics and its Applications },
volume = {389},
number = {10},
pages = {2077 - 2089},
year = {2010},
note = {},
issn = {0378-4371},
doi = {http://dx.doi.org/10.1016/j.physa.2010.01.028},
url = {http://www.sciencedirect.com/science/article/pii/S0378437110000828},
author = {Lawrence W. Lan and Yu-Chiun Chiou and Zih-Shin Lin and Chih-Cheng Hsu},
keywords = {Cellular automaton},
keywords = {Mixed traffic},
keywords = {Motorcycle },
abstract = {Modeling mixed traffic composed of motorcycles can be a challenging issue because many erratic motorcyclists may not follow the lane disciplines, particularly when traffic is congested. Based upon the refined cellular automaton (CA) model recently developed by the authors [L.W. Lan, Y.C. Chiou, Z.S. Lin, C.C. Hsu, Physica A 388 (2009) 3917–3930], this paper further proposed a sophisticated \{CA\} model to elucidate the erratic motorcycle behaviours in mixed traffic contexts. In addition to the conventional moving forward and lane-change rules, the sophisticated \{CA\} model also explicated the lateral drift behaviour for cars moving in the same lane, the lateral drift behaviour for motorcycles breaking into two moving cars, and the transverse crossing behaviour for motorcycles through the gap between two stationary cars in the same lane. Fundamental diagrams and space-time trajectories for vehicles with various car-motorcycle mixed ratios are demonstrated. }
}
@article{Chiou201397,
title = {Reprint of “Modeling two-vehicle crash severity by a bivariate generalized ordered probit approach” },
journal = {Accident Analysis & Prevention },
volume = {61},
number = {0},
pages = {97 - 106},
year = {2013},
note = {Emerging Research Methods and Their Application to Road Safety Emerging Issues in Safe and Sustainable Mobility for Older Persons The Candrive/Ozcandrive Prospective Older Driver Study: Methodology and Early Study Findings },
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2013.07.005},
url = {http://www.sciencedirect.com/science/article/pii/S000145751300273X},
author = {Yu-Chiun Chiou and Cherng-Chwan Hwang and Chih-Chin Chang and Chiang Fu},
keywords = {Two-vehicle accidents},
keywords = {Bivariate ordered probit},
keywords = {Bivariate generalized ordered probit},
keywords = {Severity level },
abstract = {Abstract This study simultaneously models crash severity of both parties in two-vehicle accidents at signalized intersections in Taipei City, Taiwan, using a novel bivariate generalized ordered probit (BGOP) model. Estimation results show that the \{BGOP\} model performs better than the conventional bivariate ordered probit (BOP) model in terms of goodness-of-fit indices and prediction accuracy and provides a better approach to identify the factors contributing to different severity levels. According to estimated parameters in latent propensity functions and elasticity effects, several key risk factors are identified—driver type (age > 65), vehicle type (motorcycle), violation type (alcohol use), intersection type (three-leg and multiple-leg), collision type (rear ended), and lighting conditions (night and night without illumination). Corresponding countermeasures for these risk factors are proposed. }
}
@article{Chiou2013405,
title = {A two-stage mining framework to explore key risk conditions on one-vehicle crash severity },
journal = {Accident Analysis & Prevention },
volume = {50},
number = {0},
pages = {405 - 415},
year = {2013},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2012.05.017},
url = {http://www.sciencedirect.com/science/article/pii/S0001457512002011},
author = {Yu-Chiun Chiou and Lawrence W. Lan and Wen-Pin Chen},
keywords = {Crash severity},
keywords = {Genetic mining rule},
keywords = {One-vehicle crashes},
keywords = {Mixed logit model},
keywords = {Stepwise rule-mining algorithm },
abstract = {This paper proposes a two-stage mining framework to explore the key risk conditions that may have contributed to the one-vehicle crash severity in Taiwan's freeways. In the first stage, a genetic mining rule (GMR) model is developed, using a novel stepwise rule-mining algorithm, to identify the potential risk conditions that best elucidate the one-vehicle crash severity. In the second stage, a mixed logit model is estimated, using the antecedent part of the mined-rules as explanatory variables, to test the significance of the risk conditions. A total of 5563 one-vehicle crash cases (226 fatalities, 1593 injuries and 3744 property losses) occurred in Taiwan's freeways over 2003–2007 are analyzed. The \{GMR\} model has mined 29 rules for use. By incorporating these 29 mined-rules into a mixed logit model, we further identify one key safe condition and four key risk conditions leading to serious crashes (i.e., fatalities and injuries). Each key risk condition is discussed and compared with its adjacent rules. Based on the findings, some countermeasures to rectify the freeway's serious one-vehicle crashes are proposed. }
}
@article{Chiou2012415,
title = {Route-based data envelopment analysis models },
journal = {Transportation Research Part E: Logistics and Transportation Review },
volume = {48},
number = {2},
pages = {415 - 425},
year = {2012},
note = {},
issn = {1366-5545},
doi = {http://dx.doi.org/10.1016/j.tre.2011.10.006},
url = {http://www.sciencedirect.com/science/article/pii/S1366554511001311},
author = {Yu-Chiun Chiou and Lawrence W. Lan and Barbara T.H. Yen},
keywords = {Route-based data envelopment analysis},
keywords = {Efficiency},
keywords = {Common inputs allocation },
abstract = {This paper proposes two novel route-based data envelopment analysis (DEA) models that jointly measure the route-level and company-level efficiencies amongst transport carriers. The core logics comprise a three-stage procedure that determines company efficiency, route efficiency and optimal allocation ratios for the common inputs. We prove that the ranking order of company performance determined by the route-based \{DEA\} model is identical to that determined by the company-based \{DEA\} model. An empirical case demonstrates the superiority of the proposed models in identifying the less efficient routs/companies as well as in reducing the input slacks without subjective conjectures. }
}
@article{Chiou2013175,
title = {Modeling two-vehicle crash severity by a bivariate generalized ordered probit approach },
journal = {Accident Analysis & Prevention },
volume = {51},
number = {0},
pages = {175 - 184},
year = {2013},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2012.11.008},
url = {http://www.sciencedirect.com/science/article/pii/S0001457512003855},
author = {Yu-Chiun Chiou and Cherng-Chwan Hwang and Chih-Chin Chang and Chiang Fu},
keywords = {Two-vehicle accidents},
keywords = {Bivariate ordered probit},
keywords = {Bivariate generalized ordered probit},
keywords = {Severity level },
abstract = {This study simultaneously models crash severity of both parties in two-vehicle accidents at signalized intersections in Taipei City, Taiwan, using a novel bivariate generalized ordered probit (BGOP) model. Estimation results show that the \{BGOP\} model performs better than the conventional bivariate ordered probit (BOP) model in terms of goodness-of-fit indices and prediction accuracy and provides a better approach to identify the factors contributing to different severity levels. According to estimated parameters in latent propensity functions and elasticity effects, several key risk factors are identified—driver type (age > 65), vehicle type (motorcycle), violation type (alcohol use), intersection type (three-leg and multiple-leg), collision type (rear ended), and lighting conditions (night and night without illumination). Corresponding countermeasures for these risk factors are proposed. }
}
@article{Wen2012193,
title = {A dynamic analysis of motorcycle ownership and usage: A panel data modeling approach },
journal = {Accident Analysis & Prevention },
volume = {49},
number = {0},
pages = {193 - 202},
year = {2012},
note = {\{PTW\} + Cognitive impairment and Driving Safety },
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2011.03.006},
url = {http://www.sciencedirect.com/science/article/pii/S0001457511000571},
author = {Chieh-Hua Wen and Yu-Chiun Chiou and Wan-Ling Huang},
keywords = {Motorcycle},
keywords = {Panel data},
keywords = {Discrete choice},
keywords = {Regression},
keywords = {Accident },
abstract = {This study aims to develop motorcycle ownership and usage models with consideration of the state dependence and heterogeneity effects based on a large-scale questionnaire panel survey on vehicle owners. To account for the independence among alternatives and heterogeneity among individuals, the modeling structure of motorcycle ownership adopts disaggregate choice models considering the multinomial, nested, and mixed logit formulations. Three types of panel data regression models – ordinary, fixed, and random effects – are developed and compared for motorcycle usage. The estimation results show that motorcycle ownership in the previous year does exercise a significantly positive effect on the number of motorcycles owned by households in the current year, suggesting that the state dependence effect does exist in motorcycle ownership decisions. In addition, the fixed effects model is the preferred specification for modeling motorcycle usage, indicating strong evidence for existence of heterogeneity. Among various management strategies evaluated under different scenarios, increasing gas prices and parking fees will lead to larger reductions in total kilometers traveled. }
}
@article{Jou2012549,
title = {Freeway drivers’ willingness-to-pay for a distance-based toll rate },
journal = {Transportation Research Part A: Policy and Practice },
volume = {46},
number = {3},
pages = {549 - 559},
year = {2012},
note = {},
issn = {0965-8564},
doi = {http://dx.doi.org/10.1016/j.tra.2011.11.012},
url = {http://www.sciencedirect.com/science/article/pii/S0965856411001819},
author = {Rong-Chang Jou and Yu-Chiun Chiou and Ke-Hong Chen and Hao-I Tan},
keywords = {Contingent valuation method},
keywords = {Spike model},
keywords = {Electronic toll collection},
keywords = {Willing-to-pay },
abstract = {This paper applies the contingent valuation method to investigate and estimate the toll rate that freeway drivers are willing-to-pay (WTP) for each unit of distance they travel, after switching from per-entry based to distance-based tolling system. Due to a large portion of respondents who are unwilling to pay a toll at all, we adopt the spike model to avoid estimation errors. The estimation results show that average willingness to pay toll is TWD1Note: 30.04 Taiwanese Dollars (TWD) was equivalent to $1 \{USD\} (October, 2011). 1 0.86/km, which can be refined further to \{TWD\} 0.81/km for short distance travelers, \{TWD\} 0.93/km for medium distance travelers, and \{TWD\} 0.97/km for long distance travelers. Additionally, the \{WTP\} toll rate of short distance travelers is significantly different on public holidays but not during peak hours. In contrast, the \{WTP\} toll rates of medium and long distance travelers significantly different during peak hours but not on public holidays. }
}
@article{Chiou2013266,
title = {The adoption behaviours of freeway electronic toll collection: A latent class modelling approach },
journal = {Transportation Research Part E: Logistics and Transportation Review },
volume = {49},
number = {1},
pages = {266 - 280},
year = {2013},
note = {},
issn = {1366-5545},
doi = {http://dx.doi.org/10.1016/j.tre.2012.09.003},
url = {http://www.sciencedirect.com/science/article/pii/S1366554512000841},
author = {Yu-Chiun Chiou and Rong-Chang Jou and Chu-Yun Kao and Chiang Fu},
keywords = {Electronic toll collection},
keywords = {Discrete choice model},
keywords = {Latent class model },
abstract = {This study develops an electronic toll collection (ETC) disaggregate choice model based on a large-scale questionnaire survey of car drivers in Taiwan. To acknowledge the difference in preferences among car drivers, the latent class logit model is used to classify respondents into different groups without subjective segmentation. The estimation results show that six groups of car drivers are optimally distinguished. The price of an e-pass and the discount for \{ETC\} tolls are identified as the two most important factors affecting \{ETC\} adoption. The study also finds that significant differences in adoption behaviours exist among groups. Effective marketing strategies for different groups are then proposed accordingly. }
}
@article{Jou201316,
title = {Freeway drivers’ willingness to pay for an on board unit under an electronic toll collection system },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {27},
number = {0},
pages = {16 - 24},
year = {2013},
note = {Selected papers from the Seventh Triennial Symposium on Transportation Analysis (TRISTAN VII) },
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/j.trc.2012.11.002},
url = {http://www.sciencedirect.com/science/article/pii/S0968090X12001350},
author = {Rong-Chang Jou and Yu-Chiun Chiou and Chung-Wei Kuo and Hao-I Tan},
keywords = {Electronic toll collection system},
keywords = {On board unit},
keywords = {Willingness to pay},
keywords = {Spike model },
abstract = {Electronic toll collection (ETC) systems have been put into practice in one or two channels at toll plazas on Taiwan’s freeways since 2006. The utilisation of the \{ETC\} system has been flat due to the extra cost of installing the on board unit (OBU) that is used in the system. To increase the utilisation rate of the \{ETC\} system, it is crucial to understand the real price that drivers are willing to pay. Therefore, this study investigates freeway drivers’ willingness to pay a value for an OBU. A stated preference experiment is designed to obtain the willingness to pay at three different levels of use. To avoid the estimation bias due to a large percentage with a zero willingness to pay, a spike model is used. Different markets are segmented to examine their willingness to pay for an OBU. The estimation results show that the willingness to pay for an \{OBU\} is NT$727/unit1Note: 30.04NT$ was equivalent to $1 \{USD\} (October, 2011). 1 for short distance drivers, NT$830 for medium distance drivers, and NT$1308/unit for long distance drivers. }
}
@article{Chiou201313,
title = {Sustainable consumption, production and infrastructure construction for operating and planning intercity passenger transport systems },
journal = {Journal of Cleaner Production },
volume = {40},
number = {0},
pages = {13 - 21},
year = {2013},
note = {Special Volume: Sustainable consumption and production for Asia: Sustainability through green design and practice },
issn = {0959-6526},
doi = {http://dx.doi.org/10.1016/j.jclepro.2010.09.004},
url = {http://www.sciencedirect.com/science/article/pii/S0959652610003549},
author = {Yu-Chiun Chiou and Lawrence W. Lan and Kai-Lin Chang},
keywords = {Sustainable transport},
keywords = {Bi-level programming},
keywords = {Game theory },
abstract = {Two bi-level programming models—an operational model and a planning model—for the intercity passenger transport systems under sustainability contexts are proposed in this study. In the upper-level models, the government (regulator) aims to provide the transport infrastructures and to regulate the fares (tolls) to achieve some sustainability objectives, indexed by energy consumption, air pollution, traffic safety, and travel time. In the lower-level models, the transport carriers aim to determine the service frequencies to maximize their profits; whereas the users aim to choose available transport modes to maximize their utilities. The rationales for the proposed models are based on the behavioral conjectures in game theory. A case of 400-km intercity passenger transport (e.g., Taipei–Kaohsiung in the western corridor of Taiwan) is exemplified with sensitivity analysis. The results indicate that rail transport is the priority mode toward overall sustainability for intercity passenger transport. Based on the results, some policy implications are addressed. }
}
@article{Jou2011945,
title = {Impacts of impression changes on freeway driver intention to adopt electronic toll collection service },
journal = {Transportation Research Part C: Emerging Technologies },
volume = {19},
number = {6},
pages = {945 - 956},
year = {2011},
note = {},
issn = {0968-090X},
doi = {http://dx.doi.org/10.1016/j.trc.2011.05.002},
url = {http://www.sciencedirect.com/science/article/pii/S0968090X11000726},
author = {Rong-Chang Jou and Yu-Chiun Chiou and Ju-Ching Ke},
keywords = {Media},
keywords = {Word-of-mouth},
keywords = {Electronic toll collection},
keywords = {Structural equations modeling },
abstract = {This paper proposes conceptual frameworks incorporating technology acceptance model, theory of planned behavior and three additional constructs – impression changes, attitude of government, and risk to investigate the factors affecting freeway driver intention to adopt electronic toll collection service for both users and nonusers of electronic toll collection. The proposed frameworks are unique because of the incorporation of media and word-of-mouth effects to represent the impression changes, respectively. The respondents were specifically asked about their impressions of electronic toll collection related policies and strategies spread through media and word-of-mouth before and after electronic toll collection operation. Estimated results obtained from structural equations modeling validate that impression changes in both media and word-of-mouth exhibit significant direct or indirect effects on freeway driver intention to adopt electronic toll collection service. Corresponding strategies to enhance electronic toll collection adoption rate are then proposed accordingly. }
}
@article{Chiou201373,
title = {Modeling crash frequency and severity using multinomial-generalized Poisson model with error components },
journal = {Accident Analysis & Prevention },
volume = {50},
number = {0},
pages = {73 - 82},
year = {2013},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2012.03.030},
url = {http://www.sciencedirect.com/science/article/pii/S0001457512001194},
author = {Yu-Chiun Chiou and Chiang Fu},
keywords = {Crash frequency},
keywords = {Crash severity},
keywords = {Multinomial-generalized Poisson},
keywords = {Error components },
abstract = {Since the factors contributing to crash frequency and severity usually differ, an integrated model under the multinomial generalized Poisson (MGP) architecture is proposed to analyze simultaneously crash frequency and severity—making estimation results increasingly efficient and useful. Considering the substitution pattern among severity levels and the shared error structure, four models are proposed and compared—the \{MGP\} model with or without error components (EMGP and \{MGP\} models, respectively) and two nested generalized Poisson models (NGP model). A case study based on accident data for Taiwan's No. 1 Freeway is conducted. The results show that the \{EMGP\} model has the best goodness-of-fit and prediction accuracy indices. Additionally, estimation results show that factors contributing to crash frequency and severity differ markedly. Safety improvement strategies are proposed accordingly. }
}
@article{Chiou2010477,
title = {A joint measurement of efficiency and effectiveness for non-storable commodities: Integrated data envelopment analysis approaches },
journal = {European Journal of Operational Research },
volume = {201},
number = {2},
pages = {477 - 489},
year = {2010},
note = {},
issn = {0377-2217},
doi = {http://dx.doi.org/10.1016/j.ejor.2009.03.005},
url = {http://www.sciencedirect.com/science/article/pii/S0377221709001490},
author = {Yu-Chiun Chiou and Lawrence W. Lan and Barbara T.H. Yen},
keywords = {Integrated data envelopment analysis},
keywords = {Non-storable commodities},
keywords = {Service effectiveness},
keywords = {Technical efficiency},
keywords = {Technical effectiveness },
abstract = {Efficiency and effectiveness for non-storable commodities represent two distinct dimensions and a joint measurement of both is necessary to fully capture the overall performance. This paper proposes two novel integrated data envelopment analysis (IDEA) approaches, the integrated Charnes, Cooper and Rhodes (ICCR) and integrated Banker, Charnes and Cooper (IBCC) models, to jointly analyze the overall performance of non-storable commodities under constant and variable returns to scale technologies. The core logic of the proposed models is simultaneously determining the virtual multipliers associated with inputs, outputs, and consumption by additive specifications for technical efficiency and service effectiveness terms with equal weights. We show that both \{ICCR\} and \{IBCC\} models possess the essential properties of rationality, uniqueness, and benchmarking power. A case analysis also demonstrates that the proposed novel \{IDEA\} approaches have higher benchmarking power than the conventional separate \{DEA\} approaches. More generalized specifications of \{IDEA\} models with unequal weights are also elaborated. }
}
@article{Chiou2009665,
title = {Integrated modeling of car/motorcycle ownership, type and usage for estimating energy consumption and emissions },
journal = {Transportation Research Part A: Policy and Practice },
volume = {43},
number = {7},
pages = {665 - 684},
year = {2009},
note = {},
issn = {0965-8564},
doi = {http://dx.doi.org/10.1016/j.tra.2009.06.002},
url = {http://www.sciencedirect.com/science/article/pii/S0965856409000640},
author = {Yu-Chiun Chiou and Chieh-Hua Wen and Shih-Hsun Tsai and Wei-Ying Wang},
keywords = {Ownership},
keywords = {Type},
keywords = {Usage},
keywords = {Energy consumption},
keywords = {Emissions },
abstract = {Devising effective management strategies to relieve dependency on private vehicles, i.e. cars and motorcycles, depends on the ability to accurately and carefully examine the effects of corresponding strategies. Disaggregate choice models regarding the ownership, type and usage of cars and motorcycles are required to achieve this. Consequently, this study proposes integrated car and motorcycle models based on a large-scale questionnaire survey of Taiwanese owners of cars and motorcycles, respectively. Incorporating gas mileage and emission coefficients for different types of cars and motorcycles into the proposed models can enable the estimation and comparison of reductions in energy consumption and emissions under various management strategies. To demonstrate the applicability of the proposed integrated models, scenarios involving 10% and 30% increases in gas prices are analyzed and compared. The results indicate that gas price elasticities of cars and motorcycles are low, ranging from 0.47 to 0.50 for cars and 0.11 for motorcycles. Additionally, a high ratio of discouraged car users shifting to use of motorcycles neutralizes the effects of increased gas price in reducing energy consumption and emissions. Pollution of \{CO\} and \{HC\} even slightly increased because motorcycles are much more polluting in terms of \{CO\} and HC. At last, the reductions of energy consumption and emissions under 10% and 30% increase (or decrease) in other manipulating variables are also estimated and compared. The countermeasures for reducing ownership and usage of cars and motorcycles are then recommended accordingly. }
}
@article{Chiou2010226,
title = {Factors influencing the intentions of passengers regarding full service and low cost carriers: A note },
journal = {Journal of Air Transport Management },
volume = {16},
number = {4},
pages = {226 - 228},
year = {2010},
note = {},
issn = {0969-6997},
doi = {http://dx.doi.org/10.1016/j.jairtraman.2009.11.005},
url = {http://www.sciencedirect.com/science/article/pii/S0969699709001021},
author = {Yu-Chiun Chiou and Yen-Heng Chen},
keywords = {Behavioral intentions},
keywords = {Low cost carriers},
keywords = {Full service carriers },
abstract = {This study investigates discrepancy in factors affecting passengers' intensions regarding using full service and low cost carriers. A conceptual model, that originally focused on the former, is adopted and slightly revised according to the service properties of low cost carriers. To validate the revised model, a questionnaire survey on passengers of Spring Airlines, the first low cost airline in China, was conducted. The results indicate differences in attitudes towards full service and low cost carriers. Service perception is a latent variable with the most significant influence on intentions about using full service carriers, but exhibits less effect on intentions regarding low cost operators. Conversely, service value exerts the greatest effect on intentions for possible low cost passengers. }
}
@article{Lan20093917,
title = {A refined cellular automaton model to rectify impractical vehicular movement behavior },
journal = {Physica A: Statistical Mechanics and its Applications },
volume = {388},
number = {18},
pages = {3917 - 3930},
year = {2009},
note = {},
issn = {0378-4371},
doi = {http://dx.doi.org/10.1016/j.physa.2009.05.039},
url = {http://www.sciencedirect.com/science/article/pii/S0378437109004245},
author = {Lawrence W. Lan and Yu-Chiun Chiou and Zih-Shin Lin and Chih-Cheng Hsu},
keywords = {Traffic flow},
keywords = {Cellular automaton},
keywords = {Refined cell},
keywords = {Limited deceleration},
keywords = {Piecewise-linear movement },
abstract = {When implementing cellular automata (CA) into a traffic simulation, one common defect yet to be rectified is the abrupt deceleration when vehicles encounter stationary obstacles or traffic jams. To be more in line with real world vehicular movement, this paper proposes a piecewise-linear movement to replace the conventional particle-hopping movement adopted in most previous \{CA\} models. Upon this adjustment and coupled with refined cell system, a new \{CA\} model is developed using the rationale of Forbes’ et al. car-following concept. The proposed \{CA\} model is validated on a two-lane freeway mainline context. It shows that this model can fix the unrealistic deceleration behaviors, and thus can reflect genuine driver behavior in the real world. The model is also capable of revealing Kerner’s three-phase traffic patterns and phase transitions among them. Furthermore, the proposed \{CA\} model is applied to simulate a highway work zone wherein traffic efficiency (maximum flow rates) and safety (speed deviations) impacted by various control schemes are tested. }
}
@article{Chiou20101057,
title = {Driver responses to green and red vehicular signal countdown displays: Safety and efficiency aspects },
journal = {Accident Analysis & Prevention },
volume = {42},
number = {4},
pages = {1057 - 1065},
year = {2010},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2009.12.013},
url = {http://www.sciencedirect.com/science/article/pii/S0001457509003273},
author = {Yu-Chiun Chiou and Chien-Hua Chang},
keywords = {Signal countdown display},
keywords = {Dilemma zone},
keywords = {Start-up delay},
keywords = {Discharge headway },
abstract = {This study investigates the effects of green signal countdown display (GSCD) and red signal countdown display (RSCD) on driver behaviours, and thus on intersection safety and efficiency. Three driver responses to GSCD, including late-stopping ratio, dilemma zone and decision to cross, and three driver responses to RSCD, including early start ratio, start-up delay, and discharge headway are observed and analyzed. Results show that although \{GSCD\} can reduce late-stopping ratio, the dilemma zone is increased by about 28 m and the decision to cross will be more inconsistent among the approaching vehicles, creating a potential risk of rear-end crashes. Additionally, following the provision of a green countdown the number of vehicles ejecting to cross the intersection reduces. On the other hand, comparisons among four observation periods examining the effects of RSCD—before-RSCD, 1.5 months after-RSCD, 3.0 months after-RSCD and 4.5 months after-RSCD, show that although \{RSCD\} significantly reduces the early start ratios of the leading vehicles in various waiting areas, the ratios soon return to their before-RSCD levels, suggesting that \{RSCD\} does not significantly improve intersection safety over the longer term. However, \{RSCD\} effectively reduces start-up delay, saturated headway, and cumulative start-up delay at 4.5 months after-RSCD installation. Thus, \{RSCD\} enhances intersection efficiency. \{RSCD\} is clearly less controversial and more beneficial than GSCD. }
}
@article{Huang2012863,
title = {Effects of multidimensional concept maps on fourth graders’ learning in web-based computer course },
journal = {Computers & Education },
volume = {58},
number = {3},
pages = {863 - 873},
year = {2012},
note = {},
issn = {0360-1315},
doi = {http://dx.doi.org/10.1016/j.compedu.2011.10.016},
url = {http://www.sciencedirect.com/science/article/pii/S0360131511002600},
author = {Hwa-Shan Huang and Chei-Chang Chiou and Heien-Kun Chiang and Sung-Hsi Lai and Chiun-Yen Huang and Yin-Yu Chou},
keywords = {Elementary education},
keywords = {Multimedia/hypermedia systems},
keywords = {Navigation},
keywords = {Teaching/learning strategies },
abstract = {This study explores the effect of multidimensional concept mapping instruction on students’ learning performance in a web-based computer course. The subjects consisted of 103 fourth graders from an elementary school in central Taiwan. They were divided into three groups: multidimensional concept map (MCM) instruction group, Novak concept map (NCM) instruction group, and traditional textbook (TT) instruction group. Four weeks of experimental instructions were given to the three groups, respectively. Students’ progresses were examined by pre-test and post-test measurements. The experimental results suggested that subjects in the \{MCM\} group performed significantly better than those in the \{NCM\} group which in turn performed significantly better than those in the \{TT\} group. Pedagogical implications were addressed, and conclusion and some suggestions were given. }
}
@article{Chiou2005617,
title = {Genetic fuzzy logic controller: an iterative evolution algorithm with new encoding method },
journal = {Fuzzy Sets and Systems },
volume = {152},
number = {3},
pages = {617 - 635},
year = {2005},
note = {},
issn = {0165-0114},
doi = {http://dx.doi.org/10.1016/j.fss.2004.11.011},
url = {http://www.sciencedirect.com/science/article/pii/S0165011404005160},
author = {Yu-Chiun Chiou and Lawrence W. Lan},
keywords = {Genetic algorithms},
keywords = {Genetic fuzzy logic controller},
keywords = {Artificial neural network},
keywords = {Fuzzy neural network},
keywords = {Car-following behaviors },
abstract = {Logic rules and membership functions are two key components of a fuzzy logic controller (FLC). If only one component is learned, the other one is often set subjectively thus can reduce the applicability of FLC. If both components are learned simultaneously, a very long chromosome is often needed thus may deteriorate the learning performance. To avoid these shortcomings, this paper employs genetic algorithms to learn both logic rules and membership functions sequentially. We propose a bi-level iterative evolution algorithm in selecting the logic rules and tuning the membership functions for a genetic fuzzy logic controller (GFLC). The upper level is to solve the composition of logic rules using the membership functions tuned by the lower level. The lower level is to determine the shape of membership functions using the logic rules learned from the upper level. We also propose a new encoding method for tuning the membership functions to overcome the problem of too many constraints. Our proposed \{GFLC\} model is compared with other similar GFLC, artificial neural network and fuzzy neural network models, which are trained and validated by the same examples with theoretical and field-observed car-following behaviors. The results reveal that our proposed \{GFLC\} has outperformed. }
}
@article{Chiou2001413,
title = {Genetic clustering algorithms },
journal = {European Journal of Operational Research },
volume = {135},
number = {2},
pages = {413 - 427},
year = {2001},
note = {Financial Modelling },
issn = {0377-2217},
doi = {http://dx.doi.org/10.1016/S0377-2217(00)00320-9},
url = {http://www.sciencedirect.com/science/article/pii/S0377221700003209},
author = {Yu-Chiun Chiou and Lawrence W.},
keywords = {Genetic algorithms},
keywords = {Clustering},
keywords = {p-Median problem },
abstract = {This study employs genetic algorithms to solve clustering problems. Three models, SICM, STCM, CSPM, are developed according to different coding/decoding techniques. The effectiveness and efficiency of these models under varying problem sizes are analyzed in comparison to a conventional statistics clustering method (the agglomerative hierarchical clustering method). The results for small scale problems (10–50 objects) indicate that \{CSPM\} is the most effective but least efficient method, \{STCM\} is second most effective and efficient, \{SICM\} is least effective because of its long chromosome. The results for medium-to-large scale problems (50–200 objects) indicate that \{CSPM\} is still the most effective method. Furthermore, we have applied \{CSPM\} to solve an exemplified p-Median problem. The good results demonstrate that \{CSPM\} is usefully applicable. }
}
@article{Chiou2006777,
title = {An artificial neural network-based expert system for the appraisal of two-car crash accidents },
journal = {Accident Analysis & Prevention },
volume = {38},
number = {4},
pages = {777 - 785},
year = {2006},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2006.02.006},
url = {http://www.sciencedirect.com/science/article/pii/S0001457506000200},
author = {Yu-Chiun Chiou},
keywords = {Accident appraisal},
keywords = {Artificial neural network},
keywords = {Discrimination analysis},
keywords = {Expert system },
abstract = {This paper employs artificial neural network (ANN) to develop an accident appraisal expert system. Two \{ANN\} models – party-based and case-based – with different hidden neurons are trained and validated by k-fold (k = 3) cross validation method. A total of 537 two-car crash accidents (1074 parties involved) are randomly and equally divided into three subsets. For the comparison, a discrimination analysis (DA) model is also calibrated. The results show that the \{ANN\} model can achieve a high correctness rate of 85.72% in training and 77.91% in validation and a low Schwarz's Bayesian information criterion (SBC) of −0.82 in training and 0.13 in validation, which indicates that the \{ANN\} model is suitable for accident appraisal. Furthermore, in order to measure the importance of each explanatory variable, a general influence (GI) index is computed based on the trained weights of ANN. It is found that the most influential variable is right-of-way, followed by location and alcoholic use. This finding concurs with the prior knowledge in accident appraisal. Thus, for the fair assessment of accident liabilities the correctness of these three key variables is of critical importance to police investigation reports. }
}
@article{Chiou2006116,
title = {Route-based performance evaluation of Taiwanese domestic airlines using data envelopment analysis },
journal = {Transportation Research Part E: Logistics and Transportation Review },
volume = {42},
number = {2},
pages = {116 - 127},
year = {2006},
note = {Selected papers from the 8th \{ATRS\} Conference },
issn = {1366-5545},
doi = {http://dx.doi.org/10.1016/j.tre.2005.09.005},
url = {http://www.sciencedirect.com/science/article/pii/S136655450500075X},
author = {Yu-Chiun Chiou and Yen-Heng Chen},
keywords = {Data envelopment analysis},
keywords = {Air routes},
keywords = {Cost efficiency},
keywords = {Cost effectiveness},
keywords = {Service effectiveness },
abstract = {This study employs data envelopment analysis (DEA) approach to evaluate the performance of domestic air routes from the perspectives of cost efficiency, cost effectiveness and service effectiveness. A total of 15 routes operated by a Taiwanese domestic airline are examined. Three input variables, two production variables and two service variables are selected from the regression analysis. The results of \{DEA\} model demonstrate that ten routes are relatively cost efficient, five routes are relatively cost effective and four routes are relatively service effective. Improvements for all inefficient routes are proposed based on their slack values. Furthermore, this study also performs agglomerative hierarchical clustering analysis to categorize the routes into four clusters according to their efficiency and effectiveness scores of three perspectives. The characteristics and directions of improvement for each cluster are analyzed and proposed. }
}
@article{Li201389,
title = {Using Geographically Weighted Poisson Regression for county-level crash modeling in California },
journal = {Safety Science },
volume = {58},
number = {0},
pages = {89 - 97},
year = {2013},
note = {},
issn = {0925-7535},
doi = {http://dx.doi.org/10.1016/j.ssci.2013.04.005},
url = {http://www.sciencedirect.com/science/article/pii/S0925753513000921},
author = {Zhibin Li and Wei Wang and Pan Liu and John M. Bigham and David R. Ragland},
keywords = {Safety},
keywords = {Crash},
keywords = {County-level},
keywords = {Geographically Weighted Regression },
abstract = {Abstract Development of crash prediction models at the county-level has drawn the interests of state agencies for forecasting the normal level of traffic safety according to a series of countywide characteristics. A common technique for the county-level crash modeling is the generalized linear modeling (GLM) procedure. However, the \{GLM\} fails to capture the spatial heterogeneity that exists in the relationship between crash counts and explanatory variables over counties. This study aims to evaluate the use of a Geographically Weighted Poisson Regression (GWPR) to capture these spatially varying relationships in the county-level crash data. The performance of a \{GWPR\} was compared to a traditional GLM. Fatal crashes and countywide factors including traffic patterns, road network attributes, and socio-demographic characteristics were collected from the 58 counties in California. Results showed that the \{GWPR\} was useful in capturing the spatially non-stationary relationships between crashes and predicting factors at the county level. By capturing the spatial heterogeneity, the \{GWPR\} outperformed the \{GLM\} in predicting the fatal crashes in individual counties. The \{GWPR\} remarkably reduced the spatial correlation in the residuals of predictions of fatal crashes over counties. }
}
@article{Park2012317,
title = {Safety effects of wider edge lines on rural, two-lane highways },
journal = {Accident Analysis & Prevention },
volume = {48},
number = {0},
pages = {317 - 325},
year = {2012},
note = {Intelligent Speed Adaptation + Construction Projects },
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2012.01.028},
url = {http://www.sciencedirect.com/science/article/pii/S0001457512000486},
author = {Eun Sug Park and Paul J. Carlson and Richard J. Porter and Carl K. Andersen},
keywords = {Safety evaluation},
keywords = {Longitudinal pavement markings},
keywords = {Empirical Bayes},
keywords = {Interrupted time series},
keywords = {Generalized linear segmented regression analysis},
keywords = {Cross-sectional analysis },
abstract = {Although it is generally expected that wider lines will have a positive effect on vehicle safety, there have not been any convincing evidence based on the crash data analysis, partly because of the lack of relevant data. In this paper, the safety effect of wider edge lines was examined by analyzing crash frequency data for road segments with and without wider edge lines. The data from three states, Kansas, Michigan, and Illinois, have been analyzed. Because of different nature of data from each state, a different statistical analysis approach was employed for each state: an empirical Bayes, before-after analysis of Kansas data, an interrupted time series design and generalized linear segmented regression analysis of Michigan data, and a cross sectional analysis of Illinois data. Although it is well-known that causation is hard to establish based on observational studies, the results from three extensive statistical analyses all point to the same findings. The consistent findings lend support to the positive safety effects of wider edge lines installed on rural, two-lane highways. }
}
@article{Pirdavani2013186,
title = {Evaluating the road safety effects of a fuel cost increase measure by means of zonal crash prediction modeling },
journal = {Accident Analysis & Prevention },
volume = {50},
number = {0},
pages = {186 - 195},
year = {2013},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2012.04.008},
url = {http://www.sciencedirect.com/science/article/pii/S0001457512001418},
author = {Ali Pirdavani and Tom Brijs and Tom Bellemans and Bruno Kochan and Geert Wets},
keywords = {Crash prediction models},
keywords = {Traffic analysis zones},
keywords = {Transportation planning},
keywords = {Travel demand management},
keywords = {Safety planning},
keywords = {Fuel-cost increase scenario},
keywords = {Activity-based models },
abstract = {Travel demand management (TDM) consists of a variety of policy measures that affect the transportation system's effectiveness by changing travel behavior. The primary objective to implement such \{TDM\} strategies is not to improve traffic safety, although their impact on traffic safety should not be neglected. The main purpose of this study is to evaluate the traffic safety impact of conducting a fuel-cost increase scenario (i.e. increasing the fuel price by 20%) in Flanders, Belgium. Since \{TDM\} strategies are usually conducted at an aggregate level, crash prediction models (CPMs) should also be developed at a geographically aggregated level. Therefore zonal crash prediction models (ZCPMs) are considered to present the association between observed crashes in each zone and a set of predictor variables. To this end, an activity-based transportation model framework is applied to produce exposure metrics which will be used in prediction models. This allows us to conduct a more detailed and reliable assessment while \{TDM\} strategies are inherently modeled in the activity-based models unlike traditional models in which the impact of \{TDM\} strategies are assumed. The crash data used in this study consist of fatal and injury crashes observed between 2004 and 2007. The network and socio-demographic variables are also collected from other sources. In this study, different \{ZCPMs\} are developed to predict the number of injury crashes (NOCs) (disaggregated by different severity levels and crash types) for both the null and the fuel-cost increase scenario. The results show a considerable traffic safety benefit of conducting the fuel-cost increase scenario apart from its impact on the reduction of the total vehicle kilometers traveled (VKT). A 20% increase in fuel price is predicted to reduce the annual \{VKT\} by 5.02 billion (11.57% of the total annual \{VKT\} in Flanders), which causes the total \{NOCs\} to decline by 2.83%. }
}
@article{Mohammadi201452,
title = {Crash frequency modeling using negative binomial models: An application of generalized estimating equation to longitudinal data },
journal = {Analytic Methods in Accident Research },
volume = {2},
number = {0},
pages = {52 - 69},
year = {2014},
note = {},
issn = {2213-6657},
doi = {http://dx.doi.org/10.1016/j.amar.2014.07.001},
url = {http://www.sciencedirect.com/science/article/pii/S2213665714000219},
author = {Mojtaba A. Mohammadi and V.A. Samaranayake and Ghulam H. Bham},
keywords = {Generalized estimation equation},
keywords = {Longitudinal analysis},
keywords = {Temporal correlation},
keywords = {Crash frequency model},
keywords = {Autocorrelation},
keywords = {Autoregressive },
abstract = {Abstract The prediction of crash frequency models can be improved when several years of crash data are utilized, instead of three to five years of data most commonly used in research. Crash data, however, generates multiple observations over the years that can be correlated. This temporal correlation affects the estimated coefficients and their variances in commonly used crash frequency models (such as negative binomial (NB), Poisson models, and their generalized forms). Despite the obvious temporal correlation of crashes, research analyses of such correlation have been limited and the consequences of this omission are not completely known. The objective of this study is to explore the effects of temporal correlation in crash frequency models at the highway segment level. In this paper, a negative binomial model has been developed using a generalized estimating equation (GEE) procedure that incorporates the temporal correlations amongst yearly crash counts. The longitudinal model employs an autoregressive correlation structure to compare to the more traditional \{NB\} model, which uses a Maximum Likelihood Estimation (MLE) method that cannot accommodate temporal correlations. The \{GEE\} model with temporal correlation was found to be superior compared to the \{MLE\} model, as it does not underestimate the variance in the coefficient estimates, and it provides more accurate and less biased estimates. Furthermore, an autoregressive correlation structure was found to be an appropriate structure for longitudinal type of data used in this study. Ten years (2002–2011) of Missouri Interstate highway crash data have been utilized in this paper. The crash data comprises of traffic characteristics and geometric properties of highway segments. }
}
@article{Xie201439,
title = {Crash frequency modeling for signalized intersections in a high-density urban road network },
journal = {Analytic Methods in Accident Research },
volume = {2},
number = {0},
pages = {39 - 51},
year = {2014},
note = {},
issn = {2213-6657},
doi = {http://dx.doi.org/10.1016/j.amar.2014.06.001},
url = {http://www.sciencedirect.com/science/article/pii/S2213665714000207},
author = {Kun Xie and Xuesong Wang and Kaan Ozbay and Hong Yang},
keywords = {Crash frequency model},
keywords = {Signalized intersection},
keywords = {Hierarchy},
keywords = {Spatial correlation},
keywords = {Hierarchical conditional autoregressive model},
keywords = {High-density network },
abstract = {Abstract Conventional crash frequency models rely on an assumption of independence among observed crashes. However, this assumption is frequently proved false by spatially related crash observations, particularly for intersection crashes observed in high-density road networks. Crash frequency models that ignore the hierarchy and spatial correlation of closely spaced intersections can lead to biased estimations. As a follow-up to our previous paper (Xie et al., 2013), this study aims to address this issue by introducing an improved crash frequency model. Data for 195 signalized intersections along 22 corridors in the urban areas of Shanghai was collected. Moran׳s I statistic of the crash data confirmed the spatial dependence of crash occurrence among the neighboring intersections. Moreover, Lagrange Multiplier test was performed and it suggested that the spatial dependence should be captured in the model error term. A hierarchical model incorporating a conditional autoregressive (CAR) effect term for the spatial correlation was developed in the Bayesian framework. A deviance information criterion (DIC) and cross-validation test were used for model selection and comparison. The results showed that the proposed model outperformed traditional models in terms of the overall goodness of fit and predictive performance. In addition, the significance of the corridor-specific random effect and \{CAR\} effect revealed strong evidence for the presence of heterogeneity across corridors and spatial correlation among intersections. }
}
@comment{{Ezra Hauer Papers}}
@article{Hauer1983287,
title = {An application of the likelihood/bayes approach to the estimation of safety countermeasure effectiveness },
journal = {Accident Analysis & Prevention },
volume = {15},
number = {4},
pages = {287 - 298},
year = {1983},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/0001-4575(83)90053-2},
url = {http://www.sciencedirect.com/science/article/pii/0001457583900532},
author = {Ezra Hauer},
abstract = {In the companion paper [Hauer, 1983] preference has been stated for the use of the likelihood function as a device for the accumulation of empirical evidence about the effect of safety countermeasures and for the Bayesian approach as a tool for presenting information to support rational decision making. The purpose of this paper is to illustrate the use of the aforementioned approaches in a concrete case. The issue at hand is the effect of a treatment for drivers convicted for driving while impaired on their rate of recidivism. Initially, expert opinion has been solicited. We find that Judges and Treatment Administrators are more optimistic about the effect of the treatment than are Psychologists and Researchers. Next, the likelihood and subjective probability distribution functions are explored on the basis of two sets of empirical evidence. This enables us to demonstrate the manner in which knowledge is accumulated and diverse opinions converge towards concensus. }
}
@article{Hauer20081634,
title = {How many accidents are needed to show a difference? },
journal = {Accident Analysis & Prevention },
volume = {40},
number = {4},
pages = {1634 - 1635},
year = {2008},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2008.03.013},
url = {http://www.sciencedirect.com/science/article/pii/S0001457508000535},
author = {Ezra Hauer},
keywords = {Safety},
keywords = {Statistics},
keywords = {Study Design },
abstract = {When a road safety study is contemplated one has establish how many accidents are needed to reach conclusions with a given level of confidence. Later, when the results are in, one has to be explicit about the confidence with which conclusions are stated. The purpose of this note is to describe a back-of-the envelop way of answering such questions with a precision that is sufficient for practical purposes. }
}
@article{Hauer20101111,
title = {On prediction in road safety },
journal = {Safety Science },
volume = {48},
number = {9},
pages = {1111 - 1122},
year = {2010},
note = {Scientific Research on Road Safety Management },
issn = {0925-7535},
doi = {http://dx.doi.org/10.1016/j.ssci.2010.03.003},
url = {http://www.sciencedirect.com/science/article/pii/S0925753510000731},
author = {Ezra Hauer},
keywords = {Prediction},
keywords = {Road safety},
keywords = {Safety targets},
keywords = {Evaluation },
abstract = {Prediction is about potential outcomes: what will happen if and what would have happened if. The first question arises when safety targets are set, the second when the effect of an intervention on safety is to be evaluated. There are many ways to predict. For the same data different prediction methods produce different predictions. What targets are set and what estimates of intervention effect are produced will depend on what method of prediction is chosen. Therefore one has to determine what method tends to predict best. To do so empirically one asks what method would have predicted best had it been applied in the past and then one assumes, inductively, that the same would apply in the future. Quantitative measures of prediction quality are suggested and it is shown how these measures of prediction quality allow one to determine which of two prediction methods should be preferred. The suggested approach was applied to two data sets: The time series of motor vehicle accident fatalities in Province A and in Province B. On the basis of this analysis one may draw tentative conclusions for these jurisdictions and the methods tested; one can say what method seems preferable, what is the average size of bias than needs to be corrected and how accurate is the prediction likely to be. Broader conclusions will emerge once many additional methods of prediction are applied to data from many other jurisdictions and pertaining to a variety of circumstances. }
}
@article{Hauer2011151,
title = {Computing what the public wants: Some issues in road safety cost–benefit analysis },
journal = {Accident Analysis & Prevention },
volume = {43},
number = {1},
pages = {151 - 164},
year = {2011},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2010.08.004},
url = {http://www.sciencedirect.com/science/article/pii/S0001457510002125},
author = {Ezra Hauer},
keywords = {Road safety},
keywords = {Cost–benefit},
keywords = {Economics},
keywords = {Evaluation},
keywords = {Welfare economics},
keywords = {Value of life},
keywords = {Discounting },
abstract = {In road safety, as in other fields, cost–benefit analysis (CBA) is used to justify the investment of public money and to establish priority between projects. It amounts to a computation by which ‘few’ – the \{CB\} analysts – aim to determine what the ‘many’ – those on behalf of which the choice is to be made – would choose. The question is whether there are grounds to believe that the tool fits the aim. I argue that the \{CBA\} tool is deficient. First, because estimates of the value of statistical life and injury on which the \{CBA\} computation rests are all over the place, inconsistent with the value of time estimates, and government guidance on the matter appears to be arbitrary. Second, because the premises of New Welfare Economics on which the \{CBA\} is founded apply only in circumstances which, in road safety, are rare. Third, because the \{CBA\} requires the computation of present values which must be questioned when the discounting is of future lives and of time. Because time savings are valued too highly when compared to life and because discounting tends to unjustifiably diminish the value of lives saved in the future, the \{CBA\} tends to bias decisions against investment in road safety. }
}
@article{Hauer2001799,
title = {Overdispersion in modelling accidents on road sections and in Empirical Bayes estimation },
journal = {Accident Analysis & Prevention },
volume = {33},
number = {6},
pages = {799 - 808},
year = {2001},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/S0001-4575(00)00094-4},
url = {http://www.sciencedirect.com/science/article/pii/S0001457500000944},
author = {Ezra Hauer},
keywords = {Empirical Bayes},
keywords = {Overdispersion},
keywords = {Negative binomial},
keywords = {Multivariate model },
abstract = {In multivariate statistical models of road safety one usually finds that the accident counts are ‘overdispersed’. The extent of the overdispersion is itself subject to estimation. It is shown that the assumption one makes about the nature of overdispersion will affect the maximum likelihood estimates of model parameters. If one assumes that the same overdispersion parameter applies to all road sections in the data base, then, the maximum likelihood estimate of parameters will be unduly influenced by very short road sections and insufficiently influenced by long road sections. The same assumption about the overdispersion parameter also leads to an inconsistency when one estimates the safety of a road section by the Empirical Bayes method. A way to avoid both problems is to estimate an overdispersion parameter (φ) that applies to a unit length of road, and to set the overdispersion parameter for a road section of length L to φL. How this would change the estimates of regression parameters for road section models now in use requires examination. Safety estimation by the Empirical Bayes method is altered substantially. }
}
@article{Hauer2004495,
title = {The harm done by tests of significance },
journal = {Accident Analysis & Prevention },
volume = {36},
number = {3},
pages = {495 - 500},
year = {2004},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/S0001-4575(03)00036-8},
url = {http://www.sciencedirect.com/science/article/pii/S0001457503000368},
author = {Ezra Hauer},
keywords = {Significance},
keywords = {Statistical hypothesis},
keywords = {Scientific method },
abstract = {Three historical episodes in which the application of null hypothesis significance testing (NHST) led to the mis-interpretation of data are described. It is argued that the pervasive use of this statistical ritual impedes the accumulation of knowledge and is unfit for use. }
}
@article{Hauer200678,
title = {The frequency–severity indeterminacy },
journal = {Accident Analysis & Prevention },
volume = {38},
number = {1},
pages = {78 - 83},
year = {2006},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2005.07.001},
url = {http://www.sciencedirect.com/science/article/pii/S0001457505001211},
author = {Ezra Hauer},
keywords = {Crash frequency},
keywords = {Crash severity},
keywords = {Older drivers},
keywords = {Trucks},
keywords = {Rollover resistance },
abstract = {Nothing is known about unreported crashes; the information we have is of reported crashes only. Whether a crash gets reported depends on its severity. It follows by logic that, using only data about reported crashes, it is impossible to say whether a change or difference in crash counts reflects a change or difference in crash frequency or in crash severity. This indeterminacy has practical implications. Examples discussed are of the misattribution of over-representation in reported crashes of older drivers and of trucks to causal factors related to the frequency of crash involvement, and of misinterpretation by researchers of findings about the rollover propensity of SUVs. }
}
@article{Hauer1990603,
title = {Preventing automobile injury. New findings from evaluation research: John D. Graham (ed.). Auburn House Publishing Company, Dover, MA, U.S.A., 1988. 287 pp. $35.00. \{ISBN\} 0-86569-185-1. },
journal = {Accident Analysis & Prevention },
volume = {22},
number = {6},
pages = {603 - 605},
year = {1990},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/0001-4575(90)90031-F},
url = {http://www.sciencedirect.com/science/article/pii/000145759090031F},
author = {Ezra Hauer}
}
@article{Hauer1983323,
title = {Bias-by-selection: The accuracy of an unbiased estimator },
journal = {Accident Analysis & Prevention },
volume = {15},
number = {5},
pages = {323 - 328},
year = {1983},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/0001-4575(83)90011-8},
url = {http://www.sciencedirect.com/science/article/pii/0001457583900118},
author = {Ezra Hauer and Philip Byer and H.C. Joksch},
abstract = {In a previous paper, a method for the elimination of bias-by-selection from before-and-after comparisons has been suggested. While the suggested estimator is unbiased, there is reason to be concerned about its precision. In this paper expressions are obtained for the variance of the unbiased estimator and the mean square error of the commonly used biased estimator. Their comparison yields conditions under which the unbiased has the smaller error. It is also shown that the sum of unbiased estimators for n sites is asymptotically normally distributed. The use of this information for significance tests and the determination of confidence limits is illustrated. }
}
@article{Hauer1992457,
title = {Empirical bayes approach to the estimation of “unsafety”: The multivariate regression method },
journal = {Accident Analysis & Prevention },
volume = {24},
number = {5},
pages = {457 - 477},
year = {1992},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/0001-4575(92)90056-O},
url = {http://www.sciencedirect.com/science/article/pii/000145759290056O},
author = {Ezra Hauer},
abstract = {There are two kinds of clues to the unsafety of an entity: its traits (such as traffic, geometry, age, or gender) and its historical accident record. The Empirical Bayes approach to unsafely estimation makes use of both kinds of clues. It requires information about the mean and the variance of the unsafety in a “reference population” of similar entities. The method now in use for this purpose suffers from several shortcomings. First, a very large reference population is required. Second, the choice of reference population is to some extent arbitrary. Third, entities in the reference population usually cannot match the traits of the entity the unsafety of which is estimated. To alleviate these shortcomings the multivariate regression method for estimating the mean and variance of unsafety in reference populations is offered. Its logical foundations are described and its soundness is demonstrated. The use of the multivariate method makes the Einpirical Bayes approach lo unsafety estimation applicable to a wider range of circumstances and yields better estimates of unsafety. The application of the method to the tasks of identifying deviant entities and of estimating the effect of interventions on unsafety are discussed and illustrated by numerical examples. }
}
@article{Persaud1997803,
title = {Crash reductions related to traffic signal removal in Philadelphia },
journal = {Accident Analysis & Prevention },
volume = {29},
number = {6},
pages = {803 - 810},
year = {1997},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/S0001-4575(97)00049-3},
url = {http://www.sciencedirect.com/science/article/pii/S0001457597000493},
author = {Bhagwant Persaud and Ezra Hauer and Richard Retting and Rama Vallurupalli and Kornel Mucsi},
keywords = {Signal removal},
keywords = {Safety evaluation},
keywords = {Empirical bayesian},
keywords = {Generalized linear modeling },
abstract = {The effect on intersection crashes of converting one-way street intersections in Philadelphia from signal to multiway stop sign control was estimated. Using crash and traffic volume data for a comparison group, regression models were computed to represent the normal crash experience of signal controlled intersections of one-way streets, by impact type, as a function of traffic volume. An empirical Bayesian procedure was used to estimate what would have been the expected number of crashes at the converted intersections had they not been converted. The empirical Bayesian estimates were compared with actual counts of crashes after conversion. Estimates were obtained for different classes of crashes categorized by impact type, day/night condition, and impact severity. Aggregate results indicate that replacing signals by multiway stop signs on one-way streets is associated with a reduction in crashes of approximately 24%, combining all severities, light conditions, and impact types. }
}
@article{Hauer19861,
title = {On the estimation of the expected number of accidents },
journal = {Accident Analysis & Prevention },
volume = {18},
number = {1},
pages = {1 - 12},
year = {1986},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/0001-4575(86)90031-X},
url = {http://www.sciencedirect.com/science/article/pii/000145758690031X},
author = {Ezra Hauer},
abstract = {We show that similar entities (drivers, intersections, bus companies, rail crossings) which in one period recorded “x” accidents do not have, on the average, “x” accidents in the subsequent period. The difference is large and systematic. This leads us to conclude that in circumstances in which only the safety estimates in these two periods matter, use of “x” to estimate the expected number of accidents has definite shortcomings. Better estimators are suggested, explored and their use is illustrated. We note that the suggested estimators are similar to what is used when estimation is based on a “treatment-control” type experimental design. It is hoped that the suggested estimators will alleviate some practical problems in the structuring of controlled experiments in safety research, eliminate bias-by-selection from uncontrolled studies and in general enhance the accuracy of safety estimates. }
}
@article{Hauer1986471,
title = {Research into the validity of the traffic conflicts technique },
journal = {Accident Analysis & Prevention },
volume = {18},
number = {6},
pages = {471 - 481},
year = {1986},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/0001-4575(86)90020-5},
url = {http://www.sciencedirect.com/science/article/pii/0001457586900205},
author = {Ezra Hauer and Per Garder},
abstract = {The use of near-misses and conflicts as an indirect measure of safety in widespread. The Traffic Conflicts Technique is one procedure for the indirect measurement of safety which has achieved a degree of formalization and attained a measure of popularity in many countries. However, doubts about the validity of the Traffic Conflicts Technique persist. In this paper we examine the conceptual foundations of indirect safety measurement when as data serve observation of events such as near-misses or conflicts. The key problem addressed is that of “validity.” A definition of what validity is to mean is suggested. The statistical machinery for the measurement of validity on the basis of empirical evidence is formulated and tested. With this, it may now be possible to move towards rational concensus about the potential of the Traffic Conflicts Technique and similar procedures for the indirect measurement of safety. As a by-product of the analytical results, a yardstick has been created by which to judge the relative performance of the many extant variants of the Traffic Conflicts Technique. }
}
@article{Hauer1983275,
title = {Reflections on methods of statistical inference in research on the effect of safety countermeasures },
journal = {Accident Analysis & Prevention },
volume = {15},
number = {4},
pages = {275 - 285},
year = {1983},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/0001-4575(83)90052-0},
url = {http://www.sciencedirect.com/science/article/pii/0001457583900520},
author = {Ezra Hauer},
abstract = {Sensible management of traffic safety is predicated on having reasonable expectations about the effect of various safety countermeasures. It is the role of evaluative research to derive such intelligence from empirical data. In spite of decades of research and experience, the safety effect of many countermeasures remains unknown. This sorry state of affairs is largely due to the objective difficulty of conducting conclusive experiments. Recognition of this objective difficulty should lead to the realization that in transport safety, knowledge is accumulated gradually from small, noisy and diverse experiments. The statistical tools used to extract knowledge from data should reflect this aspect of reality. One must therefore question the usefulness of classical tests of significance as a device for scientific progress in this field. It is argued that the unquestioning and all-pervasive use of significance testing in evaluative research on transport safety amounts to a self-inflicted learning disability. In contrast, it is shown that classical Point Estimation. Likelihood-Support and Bayesian methods can all make good use of experimental evidence which comes in small doses. In particular, the likelihood function is an efficient device for the accumulation of objective information and a necessary ingredient for Bayesian decision analysis. }
}
@article{Hauer20101128,
title = {Cause, effect and regression in road safety: A case study },
journal = {Accident Analysis & Prevention },
volume = {42},
number = {4},
pages = {1128 - 1135},
year = {2010},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/j.aap.2009.12.027},
url = {http://www.sciencedirect.com/science/article/pii/S0001457509003418},
author = {Ezra Hauer},
keywords = {Cause},
keywords = {Observational study},
keywords = {Treatment effect},
keywords = {Regression },
abstract = {Researchers use various ways to determine what change in safety is caused by some treatment. One way is to fit regression equations to cross-section data. Can this work? Another way is to do a before–after study. Is this better? I examine these questions in the setting of a case study. The treated units are rail-highway grade crossings, the treatment is the replacement of ‘crossbucks’ by ‘flashers’, and as evidence serve published papers and reports. The results of regression studies are all over the place. Still, one cannot be sure whether this is a sign that the regression failed to capture cause and effect or a sign that the effect of this treatment depends strongly on the conditions in which it is applied. As different regressions use different variables, they cannot corroborate or negate each other's results. This is deeply troubling. The results of before–after studies, in this case, are very consistent. Unfortunately the results do not apply to specific conditions and are therefore of limited practical use. In this respect crash modification functions derived from regressions would have an inherent advantage over those from before–after studies provided they captured cause and effect. There is, at present, little ground for the belief that they do. }
}
@article{Hauer1972403,
title = {Lane assignment strategies and overtaking },
journal = {Transportation Research },
volume = {6},
number = {4},
pages = {403 - 409},
year = {1972},
note = {},
issn = {0041-1647},
doi = {http://dx.doi.org/10.1016/0041-1647(72)90077-9},
url = {http://www.sciencedirect.com/science/article/pii/0041164772900779},
author = {Ezra Hauer}
}
@article{Hauer1980113,
title = {Bias-by-selection: Overestimation of the effectiveness of safety countermeasures caused by the process of selection for treatment },
journal = {Accident Analysis & Prevention },
volume = {12},
number = {2},
pages = {113 - 117},
year = {1980},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/0001-4575(80)90049-4},
url = {http://www.sciencedirect.com/science/article/pii/0001457580900494},
author = {Ezra Hauer},
abstract = {The effectiveness of safety countermeasures is often estimated from “before” and “after” accident histories of systems on which the countermeasure has been implemented. Due to practical reasons, systems are at times selected for treatment on the basis of their poor safety performance. This process of selection will ensure that on the average a reduction in the number of accidents will be observed even if the countermeasure has no effect. In this paper a robust and simple method for the estimation of this bias-by-selection is obtained. It allows elimination of the bias from research results. The dependence of the bias-by-selection on the duration of the accident history available and on the severity of the selection criterion, is explored. }
}
@article{Hauer19711,
title = {Accidents, overtaking and speed control },
journal = {Accident Analysis & Prevention },
volume = {3},
number = {1},
pages = {1 - 13},
year = {1971},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/0001-4575(71)90016-9},
url = {http://www.sciencedirect.com/science/article/pii/0001457571900169},
author = {Ezra Hauer}
}
@article{Hauer197971,
title = {Correction of license plate surveys for spurious matches },
journal = {Transportation Research Part A: General },
volume = {13},
number = {2},
pages = {71 - 78},
year = {1979},
note = {},
issn = {0191-2607},
doi = {http://dx.doi.org/10.1016/0191-2607(79)90009-8},
url = {http://www.sciencedirect.com/science/article/pii/0191260779900098},
author = {Ezra Hauer},
abstract = {To economize and to keep errors of recording in check, it is common practice in license plate surveys to record only a part of the license plate code. License plate records collected at two points in time or space are then searched for matching records. Due to the comparison or partial license plate codes some matches occur between records belonging to different vehicles. In this paper the probability distribution of such spurious matches is derived. On this basis, the importance of the phenomenon is explored. A procedure is given for the correction of survey results and the assessment of the confidence limits for corrected results. The procedure is supported by appropriate graphs and tables. }
}
@article{Hauer1982359,
title = {Traffic conflicts and exposure },
journal = {Accident Analysis & Prevention },
volume = {14},
number = {5},
pages = {359 - 364},
year = {1982},
note = {},
issn = {0001-4575},
doi = {http://dx.doi.org/10.1016/0001-4575(82)90014-8},
url = {http://www.sciencedirect.com/science/article/pii/0001457582900148},
author = {Ezra Hauer},
abstract = {The concepts “unit of exposure” and “conflict” have proven difficult to tell apart. This paper shows that when conflicts are used to measure safety and exposure is used to estimate risk, the two concepts are diametrically opposed. Conflicts can not be used to measure exposure and vice versa. The last part of the paper is devoted to the elucidation of the concept “exposure”. }
}
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