The purpose of this study was to investigate motorcycle-to-barrier crash frequency on horizontally curved roadway sections in Washington State using police-reported crash data linked with roadway data and augmented with barrier presence information. Data included 4915 horizontal curved roadway sections with 252 of these sections experiencing 329 motorcycle-to-barrier crashes between 2002 and 2011. Negative binomial regression was used to predict motorcycle-to-barrier crash frequency using horizontal curvature and other roadway characteristics. Based on the model results, the strongest predictor of crash frequency was found to be curve radius. This supports a motorcycle-to-barrier crash countermeasure placement criterion based, at the very least, on horizontal curve radius. With respect to the existing horizontal curve criterion of 820 feet or less, curves meeting this criterion were found to increase motorcycle-to-barrier crash frequency rate by a factor of 10 compared to curves not meeting this criterion. Other statistically significant predictors were curve length, traffic volume and the location of adjacent curves. Assuming curves of identical radius, the model results suggest that longer curves, those with higher traffic volume, and those that have no adjacent curved sections within 300 feet of either curve end would likely be better candidates for a motorcycle-to-barrier crash countermeasure.

Keywords: Motorcycle crash

In 2008, the state of Queensland in Australia introduced a video-based hazard perception test as part of the licensing process for new drivers. A key validity check for such a test is whether scores are associated with crash involvement. We present data demonstrating that drivers who failed the hazard perception test (based on a {ROC} curve-derived pass mark) were 25% [95% confidence interval (CI) 6%, 48%] more likely to be involved in an active crash (defined as a crash occurring while the driver’s vehicle was moving but they were not engaged in parking or reversing) during a one year period following the test (controlling for driving exposure, age, and sex). Failing drivers were also 17% (95% {CI} 6%, 29%) more likely to have been involved in active crashes prior to the test, in the period since obtaining their provisional license. These data support the proposal that the hazard perception test is a valid measure of crash-related driving performance.

Keywords: Hazard anticipation

Crash statistics suggest that horizontal curves are the most vulnerable sites for crash occurrence. These crashes are often severe and many involve at least some level of injury due to the nature of the collisions. Ensuring the desired pavement surface condition is one potentially effective strategy to reduce the occurrence of severe accidents on horizontal curves. This study sought to develop crash injury severity models by integrating crash and pavement surface condition databases. It focuses on developing a causal relationship between pavement condition indices and severity level of crashes occurring on two-lane horizontal curves in Texas. In addition, it examines the suitability of the existing Skid Index for safety maintenance of two-lane curves. Significant correlation is evident between pavement condition and crash injury severity on two-lane undivided horizontal curves in Texas. Probability of a crash becoming fatal is appreciably sensitive to certain pavement indices. Data suggested that road facilities providing a smoother and more comfortable ride are vulnerable to severe crashes on horizontal curves. In addition, the study found that longitudinal skid measurement barely correlates with injury severity of crashes occurring on curved portions. The study recommends exploring the option of incorporating lateral friction measurement into Pavement Management System (PMS) databases specifically at curved road segments.

Keywords: Injury severity

The objective of this paper is to study the contributors influencing ran-off-road (ROR) crash severities in a setting that has not been analysed in the literature, namely on freeways not designed according to the “forgiving roadside” concept. To accomplish the analysis, {ROR} crash data were collected on freeway road sections in Portugal and multinomial and mixed logit models were estimated using the driver injury and the most severely injured occupant as outcome variables. Our results are in line with previous findings reported in the literature on {ROR} crash severity in a number of distinct settings. Most importantly, this study shows the contribution of critical slopes and vehicle rollover towards fatal injuries and highlights the importance of introducing the “forgiving roadside” concept to mitigate {ROR} crash severity in Portuguese freeways. The study also indicates the importance of protecting errant vehicles particularly in horizontal curves, as these are linked with fatalities. Finally, the empirical findings from the developed models revealed problems in current Portuguese roadside design, especially with regards to criteria for forgiving slopes provision and warrants for safety barrier installation.

Keywords: Crash severity models

Motor vehicle crashes are the leading cause of death and acquired disability during the first four decades of life. While teen drivers have the highest crash risk, few studies examine the similarities and differences in teen and adult driver crashes. We aimed to: (1) identify and compare the most frequent crash scenarios—integrated information on a vehicle's movement prior to crash, immediate pre-crash event, and crash configuration—for teen and adult drivers involved in serious crashes, and (2) for the most frequent scenarios, explore whether the distribution of driver critical errors differed for teens and adult drivers. We analyzed data from the National Motor Vehicle Crash Causation Survey, a nationally representative study of serious crashes conducted by the U.S. National Highway Traffic Safety Administration from 2005 to 2007. Our sample included 642 16- to 19-year-old and 1167 35- to 54-year-old crash-involved drivers (weighted n = 296,482 and 439,356, respectively) who made a critical error that led to their crash's critical pre-crash event (i.e., event that made the crash inevitable). We estimated prevalence ratios (PR) and 95% confidence intervals (CI) to compare the relative frequency of crash scenarios and driver critical errors. The top five crash scenarios among teen drivers, accounting for 37.3% of their crashes, included: (1) going straight, other vehicle stopped, rear end; (2) stopped in traffic lane, turning left at intersection, turn into path of other vehicle; (3) negotiating curve, off right edge of road, right roadside departure; (4) going straight, off right edge of road, right roadside departure; and (5) stopped in lane, turning left at intersection, turn across path of other vehicle. The top five crash scenarios among adult drivers, accounting for 33.9% of their crashes, included the same scenarios as the teen drivers with the exception of scenario (3) and the addition of going straight, crossing over an intersection, and continuing on a straight path. For two scenarios ((1) and (3) above), teens were more likely than adults to make a critical decision error (e.g., traveling too fast for conditions). Our findings indicate that among those who make a driver critical error in a serious crash, there are few differences in the scenarios or critical driver errors for teen and adult drivers.

Keywords: Teen drivers

The increased popularity of mopeds and motor scooters in Australia and elsewhere in the last decade has contributed substantially to the greater use of powered two-wheelers (PTWs) as a whole. As the exposure of mopeds and scooters has increased, so too has the number of reported crashes involving those {PTW} types, but there is currently little research comparing the safety of mopeds and, particularly, larger scooters with motorcycles. This study compared the crash risk and crash severity of motorcycles, mopeds and larger scooters in Queensland, Australia. Comprehensive data cleansing was undertaken to separate motorcycles, mopeds and larger scooters in police-reported crash data covering the five years to 30 June 2008. The crash rates of motorcycles (including larger scooters) and mopeds in terms of registered vehicles were similar over this period, although the moped crash rate showed a stronger downward trend. However, the crash rates in terms of distance travelled were nearly four times higher for mopeds than for motorcycles (including larger scooters). More comprehensive distance travelled data is needed to confirm these findings. The overall severity of moped and scooter crashes was significantly lower than motorcycle crashes but an ordered probit regression model showed that crash severity outcomes related to differences in crash characteristics and circumstances, rather than differences between {PTW} types per se. Greater motorcycle crash severity was associated with higher (>80 km/h) speed zones, horizontal curves, weekend, single vehicle and nighttime crashes. Moped crashes were more severe at night and in speed zones of 90 km/h or more. Larger scooter crashes were more severe in 70 km/h zones (than 60 km/h zones) but not in higher speed zones, and less severe on weekends than on weekdays. The findings can be used to inform potential crash and injury countermeasures tailored to users of different {PTW} types.

Keywords: Moped

Introduction Understanding the relationships between traffic flow characteristics and crash risk under adverse weather conditions will help highway agencies develop proactive safety management strategies to improve traffic safety in adverse weather conditions. Method The primary objective is to develop separate crash risk prediction models for different weather conditions. The crash data, weather data, and traffic data used in this study were collected on the I-880N freeway in California in 2008 and 2010. This study considered three different weather conditions: clear weather, rainy weather, and reduced visibility weather. The preliminary analysis showed that there was some heterogeneity in the risk estimates for traffic flow characteristics by weather conditions, and that the crash risk prediction model for all weather conditions cannot capture the impacts of the traffic flow variables on crash risk under adverse weather conditions. The Bayesian random intercept logistic regression models were applied to link the likelihood of crash occurrence with various traffic flow characteristics under different weather conditions. The crash risk prediction models were compared to their corresponding logistic regression model. Results It was found that the random intercept model improved the goodness-of-fit of the crash risk prediction models. The model estimation results showed that the traffic flow characteristics contributing to crash risk were different across different weather conditions. The speed difference between upstream and downstream stations was found to be significant in each crash risk prediction model. Speed difference between upstream and downstream stations had the largest impact on crash risk in reduced visibility weather, followed by that in rainy weather. The {ROC} curves were further developed to evaluate the predictive performance of the crash risk prediction models under different weather conditions. The predictive performance of the crash risk model for clear weather was better than those of the crash risk models for adverse weather conditions. Impact on industry The research results could promote a better understanding of the impacts of traffic flow characteristics on crash risk under adverse weather conditions, which will help transportation professionals to develop better crash prevention strategies in adverse weather.

Keywords: Adverse weather

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.

Keywords: Aggregate traffic safety

As urbanization accelerates in Shanghai, land continues to develop along suburban arterials which results in more access points along the roadways and more congested suburban arterials; all these changes have led to deterioration in traffic safety. In-depth safety analysis is needed to understand the relationship between roadway geometric design, access features, traffic characteristics, and safety. This study examined 161 road segments (each between two adjacent signalized intersections) of eight suburban arterials in Shanghai. Information on signal spacing, geometric design, access features, traffic characteristics, and surrounding area types were collected. The effect of these factors on total crash occurrence was investigated. To account for the hierarchical data structure, hierarchical Bayesian models were developed for total crashes. To identify diverse effects on different crash injury severity, the total crashes were separated into minor injury and severe injury crashes. Bivariate hierarchical Bayesian models were developed for minor injury and severe injury to account for the correlation among different severity levels. The modeling results show that the density of signal spacing along arterials has a significant influence on minor injury, severe injury, and total crash frequencies. The non-uniform signal spacing has a significant impact on the occurrence of minor injury crashes. At the segment-level, higher frequencies of minor injury, severe injury, and total crashes tend to occur for the segments with curves, those with a higher density of access points, those with a higher percentage of heavy vehicles, and those in inner suburban areas. This study is useful for applications such as related engineering safety improvements and making access management policy.

Keywords: Suburban arterial

This study combined vehicle to vehicle crash frequency and severity estimations to examine factor impacts on Wisconsin highway safety in rainy weather. Method: Because of data deficiency, the real-time water film depth, the car-following distance, and the vertical curve grade were estimated with available data sources and a {GIS} analysis to capture rainy weather conditions at the crash location and time. Using a negative binomial regression for crash frequency estimation, the average annual daily traffic per lane, the interaction between the posted speed limit change and the existence of an off-ramp, and the interaction between the travel lane number change and the pavement surface material change were found to increase the likelihood of vehicle to vehicle crashes under rainfall. Results: However, more average daily rainfall per month and a wider left shoulder were identified as factors that decrease the likelihood of vehicle to vehicle crashes. In the crash severity estimation using the multinomial logit model that outperformed the ordered logit model, the travel lane number, the interaction between the travel lane number and the slow grade, the deep water film, and the rear-end collision type were more likely to increase the likelihood of injury crashes under rainfall compared with crashes involving only property damage. Practical implications: As an exploratory data analysis, this study provides insight into potential strategies for rainy weather highway safety improvement, specifically, the following weather-sensitive strategies: road design and {ITS} implementation for drivers' safety awareness under rainfall.

Keywords: Vehicle to vehicle

This study provides new public health data concerning the {US} commercial air tour industry. Risk factors for fatality in air tour crashes were analyzed to determine the value of the {FIA} Score in predicting fatal outcomes. Methods Using the Federal Aviation Administration's (FAA) General Aviation and Air Taxi Survey and National Transportation Safety Board data, the incidence of commercial air tour crashes from 2000 through 2010 was calculated. Fatality risk factors for crashes occurring from 2000 through 2011 were analyzed using regression methods. The {FIA} Score, Li and Baker's fatality risk index, was validated using receiver operating characteristic (ROC) curves. Results The industry-wide commercial air tour crash rate was 2.7 per 100,000 flight hours. The incidence rates of Part 91 and 135 commercial air tour crashes were 3.4 and 2.3 per 100,000 flight hours, respectively (relative risk [RR] 1.5, 95% confidence interval [CI] 1.1–2.1, P = 0.015). Of the 152 air tour crashes that occurred from 2000 through 2011, 30 (20%) involved at least one fatality and, on average, 3.5 people died per fatal crash. Fatalities were associated with three major risk factors: fire (adjusted odds ratio [AOR] 5.1, 95% {CI} 1.5–16.7, P = 0.008), instrument meteorological conditions (AOR 5.4, 95% {CI} 1.1–26.4, P = 0.038), and off-airport location (AOR 7.2, 95% {CI} 1.6–33.2, P = 0.011). The area under the {FIA} Score's {ROC} curve was 0.79 (95% {CI} 0.71–0.88). Discussion Commercial air tour crash rates were high relative to similar commercial aviation operations. Disparities between Part 91 and 135 air tour crash rates reflect regulatory disparities that require {FAA} action. The {FIA} Score appeared to be a valid measurement of fatal risk in air tour crashes. The {FIA} should prioritize interventions that address the three major risk factors identified by this study.

Keywords: Commercial air tours

Drivers outside their country of residence are at a safety disadvantage when compared to native counterparts. This research aimed to (1) investigate if out-of-state drivers in the United States experienced the same vulnerabilities as foreign drivers, and (2) examine the relations of out-of-state crashes to various human and environmental factors. Crash data from Florida, Maine, Minnesota, and Nevada was analyzed to model fault using logistic regressions. Univariate regressions showed that out-of-state drivers had increased odds of fault, ranging from 17% to 92%, for a single-vehicle crash compared to in-state drivers in all states except Florida, where there was no difference between groups. Odds were elevated for out-of-state drivers in two-vehicle crashes by 3% to 19% in all states except Florida and Minnesota, where, again, there was no difference between groups. Human and environmental factors such as age, sex, driving conditions, and seasons were examined with multivariate regressions for in- and out-of-state groups separately, and their odds ratios were compared. For single-vehicle crashes age, sex, road grade, surface condition, light conditions, and day of week were factors that increased at least one of the two groups’ odds of fault in all states. Sex, surface condition, and light conditions increased the odds of fault for at least one of the groups in two-vehicle crashes in all four states. Factors that consistently increased odds of fault for both single- and two-vehicle crashes were males, non-vehicle owners, curves, and inclement weather. Although there were several factors in each state that increased odds of fault for out-of-state drivers, no factors consistently increased odds of fault for out-of-state drivers across all four states.

Keywords: Out-of-state drivers

Crossover and rollover crashes in earth-divided, traversable medians on rural divided highways can lead to severe injury outcomes. This study estimated severity models of these two crash types. Vehicle, driver, roadway, and median cross-section design data were factors considered in the models. A unique aspect of the data used to estimate the models were the availability of median cross-slope data, which are not commonly included in roadway inventory data files. Methods A binary logit model of cross-median crash severity and a multinomial logit model of rollover crash severity were estimated using five years of data from rural divided highways in Pennsylvania. Results The highest probability of a fatal or major injury in cross-median and rollover crashes was found to occur in cases when a driver was not wearing a seatbelt. While flatter cross-slopes and narrower medians were associated with more severe cross-median crash outcomes, steeper cross-slopes and narrower medians significantly increased rollover crash severity outcomes. The presence of horizontal curves was associated with increased probabilities of high-severity outcomes in a median rollover crash. Impact on Industry Modeling results in this study confirmed that cross-median and median rollover crash severity outcomes are associated with median cross-section design characteristics. Based on the estimated models, it appears that flatter and narrower medians lead to more severe injury outcomes in cross-median crashes. Steeper median cross-slopes and narrower medians were associated with higher probabilities of more severe outcomes in median rollover crashes. The results presented in this study suggest that there is a trade-off between median cross-section design and cross-median and rollover crashes in earth-divided, traversable medians on rural divided highways. While the severity models can be included in a framework to develop design guidance in relation to this trade-off, models of crash frequency should also be considered.

Keywords: Cross-median crash severity

This study compared the characteristics of non-work and work-related crashes using linked population data on police-reported road crashes and hospital admission records in order to shed new light on the contribution of risky driving behaviour. Method A retrospective analysis was conducted of vehicle crashes involving injured car drivers and motorcyclists identified in linked police-reported and hospitalisation records during 1 January 2001–31 December 2011 in New South Wales (NSW), Australia. Working status was identified from hospitalisation records. Univariate and multiple variable logistic regression was conducted. Results There were 38,240 car drivers and motorcyclists identified, of which 10.2% were travelling for work-related purposes. For car drivers, work-related crashes were less likely to involve alcohol (OR 0.17; 95%CI 0.13–0.22) or fatigue (OR 0.80; 95%CI 0.69–0.93), occur at an intersection, or involve a dry road, but were more likely to have worn a seat belt (OR 1.66; 95%CI 1.06–2.58), occur in a metropolitan area and at speeds greater than 50 km/h than non-work-related crashes. For motorcyclists, work-related crashes were less likely to involve alcohol (OR 0.12; 95%CI 0.07–0.21) or excessive speed (OR 0.68; 95%CI 0.55–0.85), occur on a curved section of roadway, involve a dry road, or occur on roadways with speed limits of between 100 and 110 km/h, but operators were more likely to have worn a helmet (OR 2.40; 95%CI 1.24–4.66), and crashes were more likely to have occurred in a metropolitan area, than non-work-related crashes. Conclusion Alcohol, fatigue and speed are less likely to be involved in work-related vehicle crashes compared to non-work-related crashes. Individuals injured while driving for work purposes were more likely to engage in safety promoting behaviours, such as wearing a seat belt or a motorcycle helmet, compared to individuals not driving for work purposes. It appears that there could be a higher motivation to conform to safe driving behaviours for individuals while driving for work.

Keywords: Work

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.

Keywords: Crash injury severity

Driving risk varies substantially among drivers. Identifying and predicting high-risk drivers will greatly benefit the development of proactive driver education programs and safety countermeasures. The objective of this study is twofold: (1) to identify factors associated with individual driver risk and (2) predict high-risk drivers using demographic, personality, and driving characteristic data. The 100-Car Naturalistic Driving Study was used for methodology development and application. A negative binomial regression model was adopted to identify significant risk factors. The results indicated that the driver's age, personality, and critical incident rate had significant impacts on crash and near-crash risk. For the second objective, drivers were classified into three risk groups based on crash and near-crash rate using a K-mean cluster method. The cluster analysis identified approximately 6% of drivers as high-risk drivers, with average crash and near-crash (CNC) rate of 3.95 per 1000 miles traveled, 12% of drivers as moderate-risk drivers (average {CNC} rate = 1.75), and 84% of drivers as low-risk drivers (average {CNC} rate = 0.39). Two logistic models were developed to predict the high- and moderate-risk drivers. Both models showed high predictive powers with area under the curve values of 0.938 and 0.930 for the receiver operating characteristic curves. This study concluded that crash and near-crash risk for individual drivers is associated with critical incident rate, demographic, and personality characteristics. Furthermore, the critical incident rate is an effective predictor for high-risk drivers.

Keywords: Individual driver risk

In this paper, we evaluated the effects on speed and safety of the point-to-point (P2P) speed enforcement system activated on the urban motorway {A56} in Italy. The {P2P} speed enforcement is a relatively new approach to traffic law enforcement that involves the calculation of the average speed over a section. To evaluate the speed effects, we performed a before–after analysis of speed data investigating also effects on non-compliance to speed limits. To evaluate the safety effects, we carried out an empirical Bayes observational before-and-after study. The {P2P} system led to very positive effects on both speed and safety. As far as the effects on the section average travel speeds, the system yielded to a reduction in the mean speed, the 85th percentile speed, the standard deviation of speed, and the proportion of drivers exceeding the speed limits, exceeding the speed limits more than 10 km/h, and exceeding the speed limits more than 20 km/h. The best results were the decrease of the speed variability and the reduction of the excessive speeding behaviour. The decrease in the standard deviation of speed was 26% while the proportion of light and heavy vehicles exceeding the speed limits more than 20 km/h was reduced respectively by 84 and 77%. As far as the safety effects, the {P2P} system yielded to a 32% reduction in the total crashes, with a lower 95% confidence limit of the estimate equal to 22%. The greatest crash reductions were in rainy weather (57%), on wet pavement (51%), on curves (49%), for single vehicle crashes (44%), and for injury crashes (37%). It is noteworthy that the system produced a statistically significant reduction of 21% in total crashes also in the part of the motorway where it was not activated, thus generating a significant spillover effect. The investigation of the effects of the {P2P} system on speed and safety over time allowed to develop crash modification functions where the relationship between crash modification factors and speed parameters (mean speed, 85th percentile speed, and standard deviation of speed) was expressed by a power function. Crash modification functions show that the effect of speed on safety is greater on curves and for injury crashes. Even though the study results show excellent outcomes, we must point out that the crash reduction effects decreased over time and speed, speed variability, and non-compliance to speed limits significantly increased over time. To maintain its effectiveness over time, {P2P} speed enforcement must be actively managed, i.e. constantly monitored and supported by appropriate sanctions.

Keywords: Highway safety

The measurement of the temporal and local true strain behavior of polymer materials is important for the advancement in the sector of crash simulation of plastics parts. To simulate the strain rate dependent plastic material behavior of polymers under impact conditions using {FEA} (Finite Element Analysis), true stress/strain-curves at different constant strain rates are required as input data. A new approach for the measurement of true stress/strain-curves at constant strain rates is presented in this paper. The approach is based on a time based correlation method and works completely without using {FEA} based optimization procedures like inverse analysis. It only uses data measured in mechanical testing to almost automatically generate true stress/strain-curves at different constant strain rates.

Keywords: Material testing

This study examines the impact of cyclist, road and crash characteristics on the injury severity of cyclists involved in traffic crashes reported to the police in Victoria, Australia between 2004 and 2008. Logistic regression analysis was carried out to identify predictors of severe injury (serious injury and fatality) in cyclist crashes reported to the police. There were 6432 cyclist crashes reported to the police in Victoria between 2004 and 2008 with 2181 (33.9%) resulting in severe injury of the cyclist involved. The multivariate analysis found that factors that increase the risk of severe injury in cyclists involved in traffic crashes were age (50 years and older), not wearing a helmet, riding in the dark on unlit roads, riding on roads zoned 70 km/h or above, on curved sections of the road, in rural locations and being involved in head-on collisions as well as off path crashes, which include losing control of vehicle, and on path crashes which include striking the door of a parked vehicle. While this study did not test effectiveness of preventative measures, policy makers should consider implementation of programs that address these risk factors including helmet programs and environmental modifications such as speed reduction on roads that are frequented by cyclists.

Keywords: Cyclist

Introduction This paper utilizes generalized additive model to explore the potential non-linear relationship between crash frequency and exposure on different types of urban roadway segments. Methods Generalized additive models are used to analyze crash frequency data and compared with the commonly used crash rate method and generalized linear models using a five-year crash data set from Houston, Texas. Results The study shows that the relationship between crash frequency and exposure varies by segment type and the linearity may only approximately exist in certain segment types. In addition, the generalized additive modeling results suggest that such relationship curves may not be monotonic. Finally, this study demonstrates that generalized additive models in general provide better flexibility and modeling performance than generalized linear models. Impact on Industry The generalized additive model provides a very promising alternative for crash frequency modeling and other safety studies.

Keywords: Crash analysis

The influence of light level was determined for three pedestrian crash scenarios associated with three adaptive headlighting solutions—curve lighting, motorway lighting, and cornering light. These results were coupled to corresponding prevalence data for each scenario to derive measures of annual lifesaving potential. For each scenario, the risk associated with light level was determined using daylight saving time (DST) transitions to produce a dark/light interval risk ratio; prevalence was determined using the corresponding annual crash rate in darkness for each scenario. For curve lighting, pedestrian crashes on curved roadways were examined; for motorway lighting, crashes associated with high speed roadways were examined; and for cornering light, crashes involving turning vehicles at intersections were examined. In the curve analysis, lower dark/light crash ratios were observed for curved sections of roadway compared to straight roads. In the motorway analysis, posted speed limit was the dominant predictor of this ratio for the fatal crash dataset; road function class was the dominant predictor of the ratio for the fatal/nonfatal dataset. Finally, in the intersection crash analysis, the dark/light ratio for turning vehicles was lower than for nonturning vehicles; and the ratio at intersections was lower than at non-intersections. Relative safety need was determined by combining the dark/light ratio with prevalence data to produce an idealized measure of lifesaving potential. While all three scenarios suggested a potential for safety improvement, scenarios related to high speed roadway environments showed the greatest potential.

Keywords: Pedestrian collisions

{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.

Keywords: Alcohol

A traffic crash prediction model was developed to accurately estimate roadway section safety. Crash rate of a roadway section was selected as the predicting measure. Moreover, the following seven factors were selected as major influencing factors: number of years of driving, number of lanes, radius of horizontal curves, longitudinal grade, road surface status, type of intersection, and width of road surface. The traffic crash prediction model was established based on fuzzy quantitative theory. To validate the model, crash data were collected at an actual site between 490.900 km to 550.789 km on a national highway. The result from the model was in agreement with the actual field data. The conclusion is that the model can be applied to other roadway locations.

Keywords: road safety

The occupant impact velocity (OIV) and acceleration severity index (ASI) are competing measures of crash severity used to assess occupant injury risk in full-scale crash tests involving roadside safety hardware, e.g. guardrail. Delta-V, or the maximum change in vehicle velocity, is the traditional metric of crash severity for real world crashes. This study compares the ability of the OIV, ASI, and delta-V to discriminate between serious and non-serious occupant injury in real world frontal collisions. Vehicle kinematics data from event data recorders (EDRs) were matched with detailed occupant injury information for 180 real world crashes. Cumulative probability of injury risk curves were generated using binary logistic regression for belted and unbelted data subsets. By comparing the available fit statistics and performing a separate {ROC} curve analysis, the more computationally intensive {OIV} and {ASI} were found to offer no significant predictive advantage over the simpler delta-V.

Keywords: Roadside

Abstract Safety on rural highways is of great concern as nearly two third of road fatalities are found to take place on such roads. High speed of vehicles is the characteristic of rural highways. Geometry is one of the factors that control the speed of vehicles and consequently, the crash occurrence. Alignment is one of the components of geometry and an abrupt change in the alignment is a leading cause for crashes in rural highways. Presence of a curve after a long tangent or a sharp curve after a flat curve is an example for inconsistency in the alignment. Such an alignment brings about unnecessary and unhealthy speed changes that may lead to crashes. Thus, a highway design can be evaluated based on consistency in geometry. Operating speed is the measure adopted for consistency evaluation in this study. The objectives of this study are to develop operating speed models for different classes of vehicles at salient locations of multiple horizontal curves and to develop criteria for evaluating the geometric design consistency. Data of 30 sites were made use for this purpose. Multiple linear regression technique was adopted for modelling. Models were developed for the tangent section and middle of curved sections. Length of preceding tangent is the variable influencing operating speed at tangent. Radius and length of curve significantly influence operating speed at middle of first curve and radius of first and second curve influences operating speed at middle of second curve. Operating speed Deviation from Design speed (ODD) and Speed Reduction (SR) are the consistency measures and Equivalent Property Damage Only (EPDO) crashes is the safety measure used in the study for developing criteria. The criteria developed can be used to evaluate the curve as a single element, and as successive elements (combinations of tangent/curve or curve/curve). Alignment can then be classified as Good, Fair or Poor using these criteria, and it helps a designer to make suitable modifications in the design of a multiple horizontal curve from safety point of view.

Keywords: Multiple horizontal curve

Numerous efforts have been devoted to investigating crash occurrence as related to roadway design features, environmental factors and traffic conditions. However, most of the research has relied on univariate count models; that is, traffic crash counts at different levels of severity are estimated separately, which may neglect shared information in unobserved error terms, reduce efficiency in parameter estimates, and lead to potential biases in sample databases. This paper offers a multivariate Poisson-lognormal (MVPLN) specification that simultaneously models crash counts by injury severity. The {MVPLN} specification allows for a more general correlation structure as well as overdispersion. This approach addresses several questions that are difficult to answer when estimating crash counts separately. Thanks to recent advances in crash modeling and Bayesian statistics, parameter estimation is done within the Bayesian paradigm, using a Gibbs Sampler and the Metropolis–Hastings (M–H) algorithms for crashes on Washington State rural two-lane highways. Estimation results from the {MVPLN} approach show statistically significant correlations between crash counts at different levels of injury severity. The non-zero diagonal elements suggest overdispersion in crash counts at all levels of severity. The results lend themselves to several recommendations for highway safety treatments and design policies. For example, wide lanes and shoulders are key for reducing crash frequencies, as are longer vertical curves.

Keywords: Bayesian inference

The curved segments of roadways are more hazardous because of the additional centripetalforces exerted on a vehicle, driver expectations, and other factors. The safety of a curve is dependent on various factors, most notably by geometric factors, but the location of a curve in relation to other curves is also thought to influence the safety of those curves because of a driver's expectation to encounter additional curves. The link between an individual curve's geometric characteristics and its safety performance has been established, but spatial considerations are typically not included in a safety analysis. The spatial considerations included in this research consisted of four components: distance to adjacent curves, direction of turn of the adjacent curves, and radius and length of the adjacent curves. The primary objective of this paper is to quantify the spatial relationship between adjacent horizontal curves and horizontal curve safety using a crash modification factor. Doing so enables a safety professional to more accurately estimate safety to allocate funding to reduce or prevent future collisions and more efficiently design new roadway sections to minimize crash risk where there will be a series of curves along a route. The most important finding from this research is the statistical significance of spatial considerations for the prediction of horizontal curve safety. The distances to adjacent curves were found to be a reliable predictor of observed collisions. This research recommends a model which utilizes spatial considerations for horizontal curve safety prediction in addition to current Highway Safety Manual prediction capabilities using individual curve geometric features.

Keywords: Horizontal curve

Problem: Freeway entrance and exit ramp interchanges are the sites of far more crashes per mile driven than other segments of interstate highways, but the characteristics and circumstances of ramp crashes have been the subject of relatively little recent research. Method: This study examined a sample of 1,150 crashes that occurred on heavily traveled urban interstate ramps in Northern Virginia. Based on a review of diagrams and narrative descriptions from police crash reports, the most common crash types were identified and examined for different roadway locations and ramp designs and by whether at-fault drivers were entering or exiting the freeway. Results: About half of all crashes occurred when at-fault drivers were in the process of exiting interstates, 36% occurred when drivers were entering, and 16% occurred at the midpoints of access roads or on ramps connecting two interstate freeways. Three major crash types—run-off-road, rear-end, and sideswipe/cutoff—accounted for 95% of crashes in the study. The crash type most frequently associated with exiting was run-off-road, and the types most common with entering drivers were rear-end or sideswipe/cutoff. Crashes most common on ramps—run-off-road crashes—frequently occurred when vehicles were exiting interstates at night, in bad weather, or on curved portions of ramps. Speed was often a factor. Crashes occurring on ramp margins (where ramps or access roads enter or exit) were most commonly of the sideswipe/cutoff type. These often involved at-fault passenger vehicles merging from entrance ramps into the sides of large trucks already on the freeway. The predominant crash type on access roads was rear-end crashes; congestion was a factor in these crashes. Alcohol was a reported factor in a sizeable proportion of run-off-road crashes occurring on ramps (14%) and ramp margins (30%). Impact on Industry: Candidate countermeasures for run-off-road crashes include geometric design changes to increase ramp design speed such as increasing curve radii. Speed-related crashes may be reduced by the use of speed cameras accompanied by publicity. Rear-end crash countermeasures could include surveillance systems that quickly detect unexpected congestion, incident response programs, and variable message signs to alert drivers to traffic congestion ahead. Countermeasures for sideswipe/cutoff crashes could include extending the length of acceleration lanes.

Keywords: Freeway entrance and exit ramps

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.

Keywords: Association rules

Abstract Highway design which ensures that successive elements are coordinated in such a way as to produce harmonious and homogeneous driver performances along the road is considered consistent and safe. On the other hand, an alignment which requires drivers to handle high speed gradients and does not meet drivers' expectancy is considered inconsistent and produces higher crash frequency. To increase the usefulness and the reliability of existing safety performance functions and contribute to solve inconsistencies of existing highways as well as inconsistencies arising in the design phase, we developed safety performance functions for rural motorways that incorporate design consistency measures. Since the design consistency variables were used only for curves, two different sets of models were fitted for tangents and curves. Models for the following crash characteristics were fitted: total, single-vehicle run-off-the-road, other single vehicle, multi vehicle, daytime, nighttime, non-rainy weather, rainy weather, dry pavement, wet pavement, property damage only, slight injury, and severe injury (including fatal). The design consistency parameters in this study are based on operating speed models developed through an instrumented vehicle equipped with a {GPS} continuous speed tracking from a field experiment conducted on the same motorway where the safety performance functions were fitted (motorway {A16} in Italy). Study results show that geometric design consistency has a significant effect on safety of rural motorways. Previous studies on the relationship between geometric design consistency and crash frequency focused on two-lane rural highways since these highways have the higher crash rates and are generally characterized by considerable inconsistencies. Our study clearly highlights that the achievement of proper geometric design consistency is a key design element also on motorways because of the safety consequences of design inconsistencies. The design consistency measures which are significant explanatory variables of the safety performance functions developed in this study are: (1) consistency in driving dynamics, i.e., difference between side friction assumed with respect to the design speed and side friction demanded at the 85th percentile speed; (2) operating speed consistency, i.e., absolute value of the 85th percentile speed reduction through successive elements of the road; (3) inertial speed consistency, i.e., difference between the operating speed in the curve and the average operating speed along the 5 km preceding the beginning of the curve; and (4) length of tangent preceding the curve (only for run-off-the-road crashes).

Keywords: Safety performance functions

We analyse the financial crash in 2008 for different financial markets from the point of view of log-periodic function model. In particular, we consider Dow Jones index, {DAX} index and Hang Seng index. We shortly discuss the possible relation of the theory of critical phenomena in physics to financial markets.

Keywords: Log-periodic description

Abstract In relative terms, Spanish motorcyclists are more likely to be involved in crashes than other drivers and this tendency is constantly increasing. The objective of this study is to identify the factors that are related to being an offender in motorcycle accidents. A binary logit model is used to differentiate between offender and non-offender motorcyclists. A motorcyclist was considered to be offender when s/he had committed at least one traffic offense at the moment previous to the crash. The analysis is based on the official accident database of the Spanish general directorate of traffic (DGT) for the 2003–2008 time period. A number of explanatory variables including motorcyclist characteristics and environmental factors have been evaluated. The results suggest that inexperienced, older females, not using helmets, absent-minded and non-fatigued riders are more likely to be offenders. Moreover, riding during the night, on weekends, for leisure purposes and along roads in perfect condition, mainly on curves, predict offenses among motorcyclists. The findings of this study are expected to be useful in developing traffic policy decisions in order to improve motorcyclist safety.

Keywords: Motorcycle

The 1987 market crash was associated with a dramatic and permanent steepening of the implied volatility curve for equity index options, despite minimal changes in aggregate consumption. We explain these events within a general equilibrium framework in which expected endowment growth and economic uncertainty are subject to rare jumps. The arrival of a jump triggers the updating of agents' beliefs about the likelihood of future jumps, which produces a market crash and a permanent shift in option prices. Consumption and dividends remain smooth, and the model is consistent with salient features of individual stock options, equity returns, and interest rates.

Keywords: Volatility smile

Various stressors trigger cardiac death. The objective was to investigate a possible relation between a stock market crash and cardiac death in a large population within the United States. We obtained daily stock market data (Dow Jones Industrial Average Index), death certificate data for daily deaths in Los Angeles County (LA), and annual {LA} population estimates for 2005 through 2008. The 4 years death rate curves (2005 through 2008) were averaged into a single curve to illustrate annual trends. Data were “deseasonalized” by subtracting from the daily observed value the average value for that day of year. There was marked seasonal variation in total and cardiac death rates. Even in the mild {LA} climate, death rates were higher in winter versus summer including total death (+17%), circulatory death (+24%), coronary heart disease death (+28%), and myocardial infarction death (+38%) rates (p <0.0001 for each). Absolute coronary heart disease death rates have decreased since 1985. After accounting for seasonal variation, the large stock market crash in October 2008 did not affect death rates in LA. Death rates remained at or below seasonal averages during the stock market crash. In conclusion, after correcting for seasonal variation, the stock market crash in October 2008 was not associated with an increase in total or cardiac death in LA. Annual coronary heart disease death rates continue to decrease. However, seasonal variation (specifically winter) remains a trigger for death and coronary heart disease death even in {LA} where winters are mild.

Abstract To develop a practicable and clear guideline for implementing Chevrons on China’s highways, it is necessary to understand the effect of Chevrons on driving performance in different roadway geometries. Using a driving simulator, this study tests the effect of China’s Chevrons on vehicle speed and lane position on two-lane rural highway horizontal curves with different roadway geometries. The results showed a significant effect of Chevrons on speed reduction, and this function was not significantly affected by curve radius but was statistically affected by curve direction. The speed reduction caused by Chevrons was also significant at the approach of curve, middle of curve and point of tangent. The 85th percentile speed was also markedly lower when Chevrons were present. We also found a significant effect of Chevrons in encouraging participants to drive the vehicle with a more proper lane position at the first half of curves; and this function was slightly affected by curve radius. Meanwhile, the effect of Chevrons on keeping drivers staying in a more stable lane position was also statistically significant at the second half of curves. In sharp curves, the function of Chevrons to make drivers keep a stable lane position was lost. Besides, the impact of curve direction on the function of Chevrons on lane position was always present, and drivers would drive slightly away from Chevrons. Regardless of the curve radius, China’s Chevrons at horizontal curves provide an advance warning, speed control and lane position guide for traffic on the nearside of Chevrons. Besides, combing with the function of Chevrons on preventing excessive speed and the benefit to make drivers keep a more proper lane position, China’s Chevrons appear to be of great benefit to reduce crashes (e.g., run-off-road) in curves.

Keywords: Chevron alignment sign

Bends in roads can cause crashes but a recent study in the {UK} found that areas with mostly curved roads had lower crash rates than areas with straighter roads. This present study aimed to replicate the previous research in a different country. Variations in the number of fatal road crashes occurring between 1996 and 2005 in 73 territorial local authorities across New Zealand were modelled against possible predictors. The predictors were traffic flow, population counts and characteristics, car use, socio-economic deprivation, climate, altitude and road characteristics including four measures of average road curvature. The best predictors of the number of fatal crashes on urban roads, rural state highways and other rural roads were traffic flow, speed limitation and socio-economic deprivation. Holding significant factors constant, there was no evidence that {TLAs} with the most curved roads had more crashes than elsewhere. Fatal crashes on urban roads were significantly and negatively related to two measures of road curvature: the ratio of road length to straight distance and the cumulative angle turned per kilometre. Weaker negative associations on rural state highways could have occurred by chance. These results offer limited support to the suggestion that frequently occurring road bends might be protective.

Keywords: Crashes

A multivariate logistic regression model, based upon National Automotive Sampling System Crashworthiness Data System (NASS-CDS) data for calendar years 1999–2008, was developed to predict the probability that a crash-involved vehicle will contain one or more occupants with serious or incapacitating injuries. These vehicles were defined as containing at least one occupant coded with an Injury Severity Score (ISS) of greater than or equal to 15, in planar, non-rollover crash events involving Model Year 2000 and newer cars, light trucks, and vans. The target injury outcome measure was developed by the Centers for Disease Control and Prevention (CDC)-led National Expert Panel on Field Triage in their recent revision of the Field Triage Decision Scheme (American College of Surgeons, 2006). The parameters to be used for crash injury prediction were subsequently specified by the National Expert Panel. Model input parameters included: crash direction (front, left, right, and rear), change in velocity (delta-V), multiple vs. single impacts, belt use, presence of at least one older occupant (≥55 years old), presence of at least one female in the vehicle, and vehicle type (car, pickup truck, van, and sport utility). The model was developed using predictor variables that may be readily available, post-crash, from OnStar®-like telematics systems. Model sensitivity and specificity were 40% and 98%, respectively, using a probability cutpoint of 0.20. The area under the receiver operator characteristic (ROC) curve for the final model was 0.84. Delta-V (mph), seat belt use and crash direction were the most important predictors of serious injury. Due to the complexity of factors associated with rollover-related injuries, a separate screening algorithm is needed to model injuries associated with this crash mode.

Keywords: Logistic regression

Abstract Driving performance is one of the most important areas in the curve safety research because nearly all crashes on curves are associated with inappropriate driving behavior. This study developed a model to illustrate the deceleration behavior in response to the traffic sign on curves, and a simulator experiment was conducted to empirically test the model. The experiment involved three independent variables: one primary variable is the placement of the traffic sign, and two auxiliary variables are curve radius and trial number (the number of trials that the participants have conducted in the experiment). The dependent variable is the first position of releasing the accelerator pedal (FPRA). The results of the experiment showed as the same as the model indicated: when the traffic sign was placed far enough (e.g., 100 m or more) away from a curve, the {FPRA} was positively correlated with the placement of the traffic sign; however, when the traffic sign was placed near to the curve (e.g., 50 m or less from the beginning of the curve), the {FPRA} was positively correlated with the curve radius instead of the placement of the traffic sign. In addition, the more times the participants had driven in the scenario, the closer the {FPRA} to the beginning of the curve. These results imply that deceleration behavior is not only dependent on whether the drivers acquired the information, but also on the confidence level of such information. Moreover, the trial number is also related to the information perception, and influences the deceleration behavior.

Keywords: Cognition model

Motor vehicle crashes involving rural drivers aged 75 years and over are more than twice as likely to result in a serious or fatal injury as those involving their urban counterparts. The current study examined some of the reasons for this using a database of police-reported crashes (2004–2008) to identify the environmental (lighting, road and weather conditions, road layout, road surface, speed limit), driver (driver error, crash type), and vehicle (vehicle age) factors that are associated with the crashes of older rural drivers. It also determined whether these same factors are associated with an increased likelihood of serious or fatal injury in younger drivers for whom frailty does not contribute to the resulting injury severity. A number of environmental (i.e., undivided, unsealed, curved and inclined roads, and areas with a speed limit of 100 km/h or greater) and driver (i.e., collision with a fixed object and rolling over) factors were more frequent in the crashes of older rural drivers and additionally associated with increased injury severity in younger drivers. Moreover, when these environmental factors were entered into a logistic regression model to predict whether older drivers who were involved in crashes did or did not sustain a serious or fatal injury, it was found that each factor independently increased the likelihood of a serious or fatal injury. Changes, such as the provision of divided and sealed roads, greater protection from fixed roadside objects, and reduced speed limits, appear to be indicated in order to improve the safety of the rural driving environment for drivers of all ages. Additionally, older rural drivers should be encouraged to reduce their exposure to these risky circumstances.

Keywords: Older drivers

Motorcycles are frequently used in middle- and low-income societies. They are often involved in crashes, and account for a noticeable percentage of fatalities secondary to crashes. Comparing motor-vehicle occupants and motorcycle riders, the present study examined the survival hazard of crash injuries with respect to road environmental factors (i.e., area, road type, and location). We investigated the effects of such factors on survival and survival time after crashes via a binary logistic regression analysis and a Cox proportional hazard regression analysis, respectively. Results indicated that, for both motor-vehicle occupants and motorcycle riders, the fatal prevalence, occurrence likelihood, and risk based on time were decreased in urban areas and elevated on highways. The three indexes were also higher for motor-vehicle occupants on non-straight or non-level roadway sections. The prevalence of death on local roads and at intersections was relatively higher for motorcycle riders compared to motor-vehicle occupants. Speed may contribute to the survival hazard with respect to road environment factors. Speed management initiatives account for hazardous roadway, curve alignment re-examination, and increased traffic enforcement density are suggested. Collaboration among the roadway authorities, vehicle industry, and medical systems for a timely rescue is also advised. In addition, the attention to crashes at intersections and on local roads is a promising intervention for motorcycle riders.

Keywords: Survival analysis

The purpose of this study was to estimate the size of the influence of ambient light level on fatal pedestrian and vehicle crashes in three scenarios. The scenarios were: fatal pedestrian crashes at intersections, fatal pedestrian crashes on dark rural roads, and fatal single-vehicle run-off-road crashes on dark, curved roads. Each scenario's sensitivity to light level was evaluated by comparing the number of fatal crashes across changes to and from daylight saving time, within daily time periods in which an abrupt change in light level occurs relative to official clock time. The analyses included 11 years of fatal crashes in the United States, between 1987 and 1997. Scenarios involving pedestrians were most sensitive to light level, in some cases showing up to seven times more risk at night over daytime. In contrast, single-vehicle run-off-road crashes showed little difference between light and dark time periods, suggesting factors other than light level play the dominant role in these crashes. These results are discussed in the context of the possible safety improvements offered by new developments in adaptive vehicle headlighting.

Keywords: Fatal crashes

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.

Keywords: Injury severity

Abstract This study resulted in a model-averaging methodology that predicts crash injury risk using vehicle, demographic, and morphomic variables and assesses the importance of individual predictors. The effectiveness of this methodology was illustrated through analysis of occupant chest injuries in frontal vehicle crashes. The crash data were obtained from the International Center for Automotive Medicine (ICAM) database for calendar year 1996 to 2012. The morphomic data are quantitative measurements of variations in human body 3-dimensional anatomy. Morphomics are obtained from imaging records. In this study, morphomics were obtained from chest, abdomen, and spine {CT} using novel patented algorithms. A NASS-trained crash investigator with over thirty years of experience collected the in-depth crash data. There were 226 cases available with occupants involved in frontal crashes and morphomic measurements. Only cases with complete recorded data were retained for statistical analysis. Logistic regression models were fitted using all possible configurations of vehicle, demographic, and morphomic variables. Different models were ranked by the Akaike Information Criteria (AIC). An averaged logistic regression model approach was used due to the limited sample size relative to the number of variables. This approach is helpful when addressing variable selection, building prediction models, and assessing the importance of individual variables. The final predictive results were developed using this approach, based on the top 100 models in the {AIC} ranking. Model-averaging minimized model uncertainty, decreased the overall prediction variance, and provided an approach to evaluating the importance of individual variables. There were 17 variables investigated: four vehicle, four demographic, and nine morphomic. More than 130,000 logistic models were investigated in total. The models were characterized into four scenarios to assess individual variable contribution to injury risk. Scenario 1 used vehicle variables; Scenario 2, vehicle and demographic variables; Scenario 3, vehicle and morphomic variables; and Scenario 4 used all variables. {AIC} was used to rank the models and to address over-fitting. In each scenario, the results based on the top three models and the averages of the top 100 models were presented. The {AIC} and the area under the receiver operating characteristic curve (AUC) were reported in each model. The models were re-fitted after removing each variable one at a time. The increases of {AIC} and the decreases of {AUC} were then assessed to measure the contribution and importance of the individual variables in each model. The importance of the individual variables was also determined by their weighted frequencies of appearance in the top 100 selected models. Overall, the {AUC} was 0.58 in Scenario 1, 0.78 in Scenario 2, 0.76 in Scenario 3 and 0.82 in Scenario 4. The results showed that morphomic variables are as accurate at predicting injury risk as demographic variables. The results of this study emphasize the importance of including morphomic variables when assessing injury risk. The results also highlight the need for morphomic data in the development of human mathematical models when assessing restraint performance in frontal crashes, since morphomic variables are more “tangible” measurements compared to demographic variables such as age and gender.

Keywords: Anatomical morphomics

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.

Keywords: Support vector machine model

Abstract The behavior of nuclear containment structure has been studied against aircraft crash with an emphasis on the influence of strike location. The impact locations identified on the {BWR} Mark {III} type nuclear containment structure are mid-height, junction of dome and cylinder, crown of dome and arc of dome. The containment at each of the above locations has been impacted normally by Phantom F-4, Boeing 707-320 and Airbus {A320} aircrafts. The loading of the aircraft has been assigned through the corresponding reaction-time response curve. ABAQUS/Explicit finite element code has been used to carry out the three-dimensional numerical simulations. The concrete damaged plasticity model was used to simulate the behavior of concrete while the behavior of steel reinforcement was incorporated using the Johnson–Cook elasto-viscoplastic material model. The mid-height of containment has been found to experience most severe deformation against each aircraft. Phantom {F4} has been found to be most disastrous at each location. The results have been compared with those of the available studies with respect to the containment deformation.

Background In San Juan County, New Mexico, a 28-day jail/treatment program for first-time driving-while-intoxicated (DWI) offenders was established in 1994 to reduce both {DWI} recidivism and alcohol-related crashes. This paper assesses the impact of the program on both outcomes. Methods The data are composed of driving records of all people arrested for {DWI} in San Juan County from August 1994 through December 2001. Subsequent re-arrests and crashes were analyzed to compare people who had been sentenced to the jail/treatment program and those who had not. Kaplan–Meier survival curves and Cox proportional hazards regression analyses were used. Covariates included age, gender, blood alcohol content (BAC), number of prior arrests, and ethnicity (Native American, non-Hispanic white, and Hispanic). Results Re-arrest rates were significantly lower for the treatment than the nontreatment group. Each of the three major ethnic groups showed similar effects. This was not observed for subsequent alcohol-related crashes, possibly as a result of insufficient numbers. {BAC} and number of previous arrests were, however, significant risk factors for subsequent crashes. Finally, although {BAC} and previous arrests were important risk factors for subsequent crashes, the vast majority of subsequent alcohol-related crashes occurred among people in the intermediate risk ranges. Conclusions The jail/treatment program is effective in reducing the probability of {DWI} re-arrests. The evidence with respect to crashes is equivocal. That most crashes occur to people in the intermediate risk range exemplifies the prevention paradox, and means that the courts, which deal most severely with high-risk individuals, cannot be expected to have a major impact on alcohol-related crashes.

To identify factors influencing severity of injury to older drivers in fixed object–passenger car crashes, two sets of sequential binary logistic regression models were developed. The dependent variable in one set of models was driver injury severity, whereas for the other it was the crash severity (most severe injury in the crash). For each set of models, crash or injury severity was varied from the least severity level (no injury) to the highest severity level (fatality) and vice versa. The source of data was police crash reports from the state of Florida. The model with the best fitting and highest predictive capability was used to identify the influence of roadway, environmental, vehicle, and driver related factors on severity. Travel speed, restraint device usage, point of impact, use of alcohol and drugs, personal condition, gender, whether the driver is at fault, urban/rural nature and grade/curve existence at the crash location were identified as the important factors for making an injury severity difference to older drivers involved in single vehicle crashes.

Keywords: Older drivers

Abstract The strain rate dependency of carbon fibre reinforced plastic (CFRP) laminate manufactured in a resin transfer moulding (RTM) process was investigated up to strain rates of 102 s-1. High-speed video imaging in combination with digital image correlation analysis and high-speed infrared cameras were applied to evaluate the tests. Specimens were specifically designed for tests at high loading rates. Periodic strain localisations were observed. Thus, multiple fractures occurred at the highest strain rate. Considerable strain rate dependence could be identified. The stress-strain curves, and in case of 90° tension and compression also the strain to fracture rise moderately with increasing strain-rate. High-rate shear tests at ±45° loading direction with large, localised deformations up to failure showed reduced hardening compared to quasi-static tests, probably caused by adiabatic heating. A local temperature rise of about 50 K was determined by high-speed infrared measurements.

Keywords: {CFRP} laminate

Abstract Prediction of failure in metal sheets is an important topic for the sheet forming community, as well as for the automotive crash community. The word ‘failure’ can have different meaning for different individuals within these communities. Methods for failure prediction within this area can either focus on the prediction of plastic instability (necking), or on the actual fracture phenomenon. The pros and cons of these approaches are discussed in this paper. The current authors have chosen to favour methods for necking prediction. The traditional method for necking prediction is to use a limit curve in the principal strain space (FLD). The great disadvantage of this approach is that it is only applicable for linear strain paths. In fact, the necking phenomenon can be shown to be strongly strain path dependent. In the current report, four different numerical methods for instability prediction are discussed, and compared in applications to some simple problems involving broken strain paths. It is shown that these methods can yield dramatically different results in some particular cases. Based on the findings of this study, the paper concludes with some recommendations for how the failure prediction problem best can be handled in industrial sheet forming and crash simulations.

Keywords: Sheet metal

Abstract Adaptive headlights swivel with steering input to keep the beams on the roadway as drivers negotiate curves. To assess the effects of this feature on driver’s visual performance, a field experiment was conducted at night on a rural, unlit, and unlined two-lane road during which 20 adult participant drivers searched a set of 60 targets. High- (n = 30) and low- (n = 30) reflectance targets were evenly distributed on straight road sections and on the inside or outside of curves. Participants completed three target detection trials: once with adaptive high-intensity discharge (HID) headlights, once with fixed {HID} headlights, and once with fixed halogen headlights. Results indicated the adaptive {HID} headlights helped drivers detect targets that were most difficult to see (low reflectance) at the points in curves found by other researchers to be most crucial for successful navigation (inside apex). For targets placed on straight stretches of road or on the outside of curves, the adaptive feature provided no significant improvement in target detection. However, the pattern of results indicate that {HID} lamps whether fixed or adaptive improved target detection somewhat, suggesting that part of the real world crash reduction measured for this adaptive system (Highway Loss Data Institute (HLDI), 2012a) may be due to the differences in the light source (HID vs. halogen). Depending on the scenario, the estimated benefits to driver response time associated with the tested adaptive (swiveling HID) headlights ranged from 200 to 380 ms compared with the fixed headlight systems tested.

Keywords: Traffic safety

To facilitate the assessment of hip injury risk in frontal motor-vehicle crashes, an injury risk curve that relates peak force transmitted to the hip to the probability of hip fracture was developed by using survival analysis to fit a lognormal distribution to a recently published dataset of hip fracture forces. This distribution was parameterized to account for the effect of subject stature, which was the only subject characteristic found to significantly affect hip fracture force (X2(1)=6.03, p=0.014). The distribution was further parameterized to account for the effects of hip flexion and abduction from a standard driving posture on hip fracture force using relationships between mean hip fracture force and hip flexion/abduction reported in the literature. The resulting parametric distribution was used to define relationships between force applied to the hip and the risk of hip fracture for the statures associated with the small female, midsize male, and large male crash-test dummies, thus allowing these dummies to assess hip fracture/dislocation risk in frontal crashes, provided that such dummies are sufficiently biofidelic. For the midsize male crash test dummy, a 50% risk of hip fracture was associated with a force of 6.00 kN. For the small female and large male dummies, a 50% risk of hip fracture was associated with forces of 4.46 and 6.73 kN, respectively.

Keywords: Hip fracture

Injury risk curves for the skeletal knee–thigh–hip (KTH) relate peak force applied to the anterior aspect of the flexed knee, the primary source of {KTH} injury in frontal motor-vehicle crashes, to the probability of skeletal {KTH} injury. Previous {KTH} injury risk curves have been developed from analyses of peak knee-impact force data from studies where knees of whole cadavers were impacted. However, these risk curves either neglect the effects of occupant gender, stature, and mass on {KTH} fracture force, or account for them using scaling factors derived from dimensional analysis without empirical support. A large amount of experimental data on the knee-impact forces associated with {KTH} fracture are now available, making it possible to estimate the effects of subject characteristics on skeletal {KTH} injury risk by statistically analyzing empirical data. Eleven studies were identified in the biomechanical literature in which the flexed knees of whole cadavers were impacted. From these, peak knee-impact force data and the associated subject characteristics were reanalyzed using survival analysis with a lognormal distribution. Results of this analysis indicate that the relationship between peak knee-impact force and the probability of {KTH} fracture is a function of age, total body mass, and whether the surface that loads the knee is rigid. Comparisons between injury risk curves for the midsize adult male and small adult female crash test dummies defined in previous studies and new risk curves for these sizes of occupants developed in this study suggest that previous injury risk curves generally overestimate the likelihood of {KTH} fracture at a given peak knee-impact force. Future work should focus on defining the relationships between impact force at the human knee and peak axial compressive forces measured by load cells in the crash test dummy {KTH} complex so that these new risk curves can be used with ATDs.

Keywords: Biomechanics

Motor vehicle crashes (MVC) are a leading public health problem. Improving notification times and the ability to predict which crashes will involve severe injuries may improve trauma system utilization. This study was undertaken to develop and validate a model to predict severe head injury following {MVC} using information readily incorporated into an automatic crash notification system. A cross-sectional study with derivation and validation sets was performed. The cohort was drawn from drivers of vehicles involved in {MVC} obtained from the National Automotive Sampling System (NASS). Independent multivariable predictors of severe head injury were identified. The model was able to stratify drivers according to their risk of severe head injury indicating its validity. The areas under the receiver-operating characteristic (ROC) curves were 0.7928 in the derivation set and 0.7940 in the validation set. We have developed a prediction model for head injury in MVC. As the development of automatic crash notification systems improves, models such as this one will be necessary to permit triage of what would be an overwhelming increase in crash notifications to pre-hospital responders.

Keywords: Head injury

This paper uses a semi-parametric Poisson-gamma model to estimate the relationships between crash counts and various roadway characteristics, including curvature, traffic levels, speed limit and surface width. A Bayesian nonparametric estimation procedure is employed for the model’s link function, substantially reducing the risk of a mis-specified model. It is shown via simulation that little is lost in terms of estimation quality if the nonparametric estimation procedure is used when standard parametric assumptions (e.g., linear functional forms) are satisfied, but there is significant gain if the parametric assumptions are violated. It is also shown that imposing appropriate monotonicity constraints on the relationships provides better function estimates. Results suggest that key factors for explaining crash rate variability across roadways are the amount and density of traffic, presence and degree of a horizontal curve, and road classification. Issues related to count forecasting on individual roadway segments and out-of-sample validation measures also are discussed.

Keywords: Forecasting

Abstract Due to their draping, stiffness, improved ductility and damage tolerance properties woven composites are being increasingly used for the construction of crash-relevant structural parts. Textile composites may depict a nonlinear behavior along several directions. Moreover, considerably-thick composite structures are likely to be used in order to increase energy absorption and to comply with the crash validation criteria. Therefore, a nonlinear numerical material model for textile composite materials has been developed for shells and thick shells. The model has been implemented as a user-defined subroutine (UMAT) in the LS-DYNA finite element code featuring with explicit time integration. The nonlinear behavior until failure is modeled in each in-plane material direction by a user-defined load curve or the Ramberg–Osgood equation. A plasticity formulation coupled with the nonlinearity accounts for permanent deformations. The failure is predicted using either a maximal stress criterion or the quadratic Tsai–Wu criterion. In order to model damage propagation, different post-failure damage definitions have been developed and implemented for each main in-plane material direction. A smeared formulation ensures the mesh independence in the presence of strain localization. The model has been assessed using characterization tensile and compressive tests on plain-weave and twill-weave carbon fiber composites.

Keywords: Woven

Abstract The effect of temperature and strain rate on the mechanical behavior of a commercial dual phase steel (DP 800) has been investigated experimentally by uniaxial tensile tests in this study, covering temperatures (−60 °C to 100 °C) and strain rates (1×10–4 to 1×102 s−1) encompassing conditions experienced in automotive crash situations. Yield and ultimate tensile strength, ductility, temperature effects and strain rate sensitivity have been determined and discussed. It was found that the Voce equation [σ=σs−(σs−σ0)exp(−εθ0/σs))] can be satisfactorily applied to describe the tensile flow curves by means of a modified Kocks–Mecking model. In this model the parameter θ0 is fixed, whereas both σ0 and σs consist of athermal and thermal stress components. The athermal component is only weakly dependent on temperature through the elastic shear modulus μ. The thermal stress component is governed by temperature and strain rate. Statistical analysis based on the experimental data has allowed all parameters in the Voce equation to be quantified.

Keywords: Dual phase steel

Polymers are widely used in protection systems, e.g. in cars. For dimensioning those parts, crash simulation is performed. However, crash simulation programs require reliable high rate mechanical properties to provide accurate results. As polymers are viscoelastic materials Young's modulus and yield stress are rate dependent quantities. In order to determine these properties, special experimental devices and special evaluation methods have to be used. In this paper, the modification of the clamps of a servo-hydraulic tensile testing machine to reach a global strain rate of 670/s is described. Furthermore, a new evaluation method is shown to determine Young's modulus and yield stress using a curve fitting procedure. The results show that both Young's modulus and yield stress depend logarithmically on the strain rate. It is also shown that the rate dependency of the Young's modulus can be used to get rid of the stress oscillations superimposed on the stress signal.

Keywords: High speed tensile testing

In this paper we present a complete study of the (N + 1)-body ring problem. In particular, we review and describe the evolution of the equilibrium points, their stability, their bifurcations, the zero velocity curves and we provide new techniques that give new views to this classical problem. Some of these techniques are the {OFLI2} (a Chaos Indicator given in [Barrio R. Sensitivity tools vs. Poincaré sections. Chaos, Solitons & Fractals 2005;25(3):711–26; Barrio R. Painting chaos: a gallery of sensitivity plots of classical problems. Int J Bifur Chaos Appl Sci Eng [in press]]) and the Crash Test [Nagler J. Crash test for the restricted three-body problem. Phys Rev E (3) 2005;71(2):026227, 11; Nagler J. Crash test for the Copenhagen problem. Phys Rev E (3) 2004;69(6):066218, 6]. With the {OFLI2} we have studied the chaoticity of the orbits and with the Crash Test we have classified the orbits as bounded, escape or collisions. Finally, we have performed a systematic search of symmetric periodic orbits of the system, locating much more orbits that in previous studies of other authors.

Abstract A kinematically admissible mechanism is presented for the progressive collapse of a foam-filled and unfilled circular frustum. The mechanism uses a three-limb model of collapse for the frustum shell, taking into account the plastic strain and circumferential strain energy dissipation during collapse. For the foam-filled case, the energy dissipation due to the plastic collapse of the foam and the interaction effects between it and outer frustum shell were considered. To account for the interaction effects, a pressure equivalent to the stress plateau of the foam was applied only to the inward bending proportion of the frustum. This is the result of our extensive experimental studies, which shows that Poisson's effects are negligible and that there will be no transverse strains resulting from the axial collapse of the frustum. We have further conducted analysis of empty frustum. A comparative analysis for the developed mechanism and previously conducted experimental studies showed good agreement between the two. Lastly, a parametric study of the mechanism correctly predicts that the magnitude of the crushing load depends on the length and proportion of the inward folds. Our upper-bound model gives a closed form solution for the collapse of foam-filled and unfilled frusta that can be used for crash energy management in automobiles.

Keywords: Frustum

Curve crashes are a particular matter of concern regarding motorcycle riding safety. For this reason, an intelligent Curve Warning system has been designed that gives the riders support when negotiating a curve. The system has been tested in a simulator study carried out with 20 test riders. The subjects performed three rides: one without the system (baseline) and two experimental rides using a version of the Curve Warning system, one providing the warnings by a force feedback throttle and one by a haptic glove. The effects of the two system versions were evaluated both in terms of the simulated riding performance and the subjective assessment by the riders. A descriptive analysis of the riders’ reactions to the warnings shows that the warnings provided by both system versions provoke an earlier and stronger adaptation of the motorcycle dynamics to the curve than when the riders do not use the system. Riding with the Curve Warning system with the haptic glove furthermore leads to a reduction of critical curve events. The riders’ subjective workload level was not affected by the system use, whereas the Curve Warning system with the force feedback throttle required an increased attention. The comparison of the riders’ opinions about the system reveals a preference of the Curve Warning system with the haptic glove. The better acceptance of this system version suggests a higher potential in the enhancement of riding safety.

Keywords: Motorcycle

Introduction A high percentage of drivers who die as a result of a single vehicle crash are under the influence of alcohol. We aimed to better understand the prevalence of these fatalities and the ratio of death to injuries based on various risk factors. We focused on alcohol-related and -unrelated single-vehicle crashes to investigate the influence of such risk factors on the time until death for car and motorcycle drivers. Methods We combined data from national police reports and a vital registration database in Taiwan. Survival analysis using Cox regression models was used to identify the risk factors of time until death. Results Overall, nearly 60% of car driver fatalities and 40% of motorcycle driver fatalities involved the consumption of alcohol. Survival analysis of single-vehicle crashes suggested that the traffic island separation between a car moving at a higher speed and motorcycle traffic resulted in a higher risk of death over time for motorcycle drivers who consumed alcohol. The factors attributed to a higher risk of death over time for motorcycle drivers were older age, crashing into trees, night-time driving, driving on curved roads, and driving on local roads. Driving without restraints and driving on roads with higher speed limits attributed to a higher risk of death over time for car drivers. Conclusions The factors that influence the risk of death over time in a motor-vehicle accident involving alcohol depended on different elements, which should each be considered when attempting to reduce this risk. Impact on Industry More efforts should be made to investigate the various risk factors in areas with large motorcycle populations.

Keywords: Alcohol

In this paper, we present a numerical technique to simulate the crash behaviour of laminated safety glass via finite elements. As the main aspect of this work, we consider two coincided elements: a shell element for glass and a membrane element for the hyperelastic PVB-interlayer. We give an overview of hyperelastic models, which are used in crash simulations and investigate the material laws by Blatz–Ko, Mooney–Rivlin and Ogden. The obtained stress–strain curves are fitted by experimental results of the interlayer. For a comparison, we use an one-material-model with piecewise linear plasticity and a laminated glass model assigning material properties to the integration points. As practical applications, we simulate an impact of a sphere into a glass plate and investigate the behaviour of a windscreen during a roof crash.

Keywords: Safety glass

This paper presents a crashworthiness design of regular multi-corner thin-walled columns with different types of cross-sections and different profiles, including straight octagonal columns and curved hexagonal columns. In this paper, the straight octagonal section columns are first optimized, which mainly take axial crash loads during crashes. Next, the curved hexagonal section columns are optimized following the same approach, which are subject to bending moment when impact occurs. During the design optimizations, specific energy absorption (SEA) is set as the design objective, side length of the cross-sections and wall thickness are selected as design variables, and maximum crushing force (Pm) is set as the design constraint. Both the objective and constraint are formulated using the response surface method (RSM) based on sets of finite element (FE) results obtained from {FE} analyses (FEA). After obtaining the optimal designs, parametric studies are performed to investigate the influences of the design variables on the crash performance of such multi-corner thin-walled columns.

Keywords: Crashworthiness design

This paper presents a disaggregate approach to crash rate analysis. Enumerating crash rates on a per trip-kilometer basis, the proposed method removes the linearity assumption inherent in the conventional quotient indicator of accidents per unit travel distance. The approach involves combining two disparate datasets on a geographic information systems (GIS) platform by matching accident records to a defined travel corridor. As an illustration of the methodology, travel information from the Victorian Activity and Travel Survey (VATS) and accident records contained in CrashStat were used to estimate the crash rates of Melbourne residents in different age–sex groups according to time of the day and day of the week. The results show a polynomial function of a cubic order when crash rates are plotted against age group, which contrasts distinctly with the U-shape curve generated by using the conventional aggregate quotient approach. Owing to the validity of the many assumptions adopted in the computation, this study does not claim that the results obtained are conclusive. The methodology, however, is seen as providing a framework upon which future crash risk measures could be based as the use of spatial tracking devises become prevalent in travel surveys.

Keywords: Disaggregate crash rate

An overview of the characteristics of traffic crashes among young, middle-aged and older drivers is presented. The results suggest that the youngest and the oldest drivers were more likely to be considered at-fault. With respect to crash characteristics, older drivers were less likely to have crashes involving driver fatigue, during the evening and early morning, on curved roads, during adverse weather, involving a single vehicle, and while traveling at high speeds. Conversely, older drivers were over-represented in crashes at intersections and/or involving failure to yield the right of way, unseen objects, and failure to heed stop signs or signals. Crashes occurring while turning and changing lanes were also more common among older drivers. Alcohol was less likely to be a factor in traffic crashes involving older adults. Synthesizing these results led to the conclusion that the primary problem with the young is risk-taking and lack of skill. The strength of older drivers lies in their aversion to risk, but perceptual problems and difficulty judging and responding to traffic flow often counterbalance this attribute.

Keywords: Accidents

Abstract A run-off-road (ROR) event occurs when one or more of a vehicle’s wheels leaves the roadway and begins to travel on the surface or shoulder adjacent to the road. Despite various countermeasures, {ROR} crashes continue to yield a large number of fatalities and injuries. Infrastructure-based solutions do not directly address the critical factor of driver performance preceding and during an {ROR} event. In this study, a total of 75 individuals participated in a pre–post experiment to examine the effect of a training video on improving driver performance during a set of simulated {ROR} scenarios (e.g., on a high speed highway, a horizontal curve, and a residential rural road). In each scenario, the vehicle was unexpectedly forced into an {ROR} scenario for which the drivers were instructed to recover as safely as possible. The treatment group then watched a custom {ROR} training video while the control group viewed a placebo video. The participants then drove the same simulated {ROR} scenarios. The results suggest that the training video had a significant positive effect on drivers’ steering response on all three roadway conditions as well as improvements in vehicle stability, subjectively rated demand on the driver, and self-evaluated performance in the highway scenario. Under the highway conditions, the treatment group reduced the frequency of spinouts from 70% in the pre-training events to 16% in the post-training events (χ2(1) = 23.32, p < 0.001) with no significant improvement found for the control group. In the horizontal curve, spinouts were reduced for the treatment group from 50% in the pre-training events to 30% in the post-training events (χ2(1) = 8.45, p = 0.004) with the control group also not showing any significant improvement. The results of this study suggest that even a short video about recovering from {ROR} events can significantly influence a driver’s ability to recover. It is possible that additional training may have further benefits in recovering from {ROR} events.

Keywords: Automotive safety

Abstract We present an analysis of the {USA} stock market using a simple fractal function. Financial bubbles preceding the 1987, 2000 and 2007 crashes are investigated using the Besicovitch–Ursell fractal function. Fits show a good agreement with the S&P 500 data when a complete financial growth is considered, starting at the threshold of the abrupt growth and ending at the peak. Moving the final time of the fitting interval towards earlier dates causes growing discrepancy between two curves. On the basis of a detailed analysis of the financial index behavior we propose a method for identifying the stage of the current financial growth and estimating the time in which the index value is going to reach the maximum.

Keywords: Econophysics

Abstract Invasions by exotic species are generally described using a logistic growth curve divided into three phases: introduction, expansion and saturation. This model is constructed primarily from regional studies of plant invasions based on historical records and herbarium samples. The goal of this study is to compare invasion curves at the local scale to the logistic growth curve using long-term datasets. Five datasets ranging 41–86 years in length were recovered from five sites in four western states. Data for the following seven exotic species were analyzed using regression analysis to evaluate fit to a non-linear sigmoidal logistic curve: crested wheatgrass (Agropyron cristatum), dwarf alyssum (Alyssum desertorum), cheatgrass (Bromus tectorum), Lehmann lovegrass (Eragrostis lehmanniana), halogeton (Halogeton glomeratus), Russian thistle (Salsola tragus) and tumble mustard (Sisymbrium altissimum). A greater variety of curve shapes was documented by long-term datasets than those published based on herbaria sampling. Only two species from three different sites and with three different data types met the criteria for fitting a logistic curve. Many of the other species/location combinations were characterized by sporadic spikes and crashes. The general lack of fit with the model may be the results of the complex interactions that drive vegetation change in rangeland environments.

Keywords: Disturbance

Characteristics of the driver, roadway environment, and vehicle were associated with the likelihood of rollover occurrence in more than 14 000 single-vehicle fatal and 78 000 single-vehicle injury crashes during 1995–98. Rollovers were more likely in crashes involving young drivers or occurring on rural curves. After accounting for the effects of driver age and gender, roadway alignment and surface condition, and whether or not the crash occurred in a rural area, light trucks were still twice as likely as cars to experience rollovers. Some light truck models were much more likely than others to experience rollovers. However, while physical differences (e.g. center of gravity height) could explain some of this variability, other factors affecting vehicle stability may be evident only after dynamic testing.

Keywords: Rollover

Motor-vehicle crashes are the leading cause of fetal deaths resulting from maternal trauma in the United States, and placental abruption is the most common cause of these deaths. To minimize this injury, new assessment tools, such as crash-test dummies and computational models of pregnant women, are needed to evaluate vehicle restraint systems with respect to reducing the risk of placental abruption. Developing these models requires accurate material properties for tissues in the pregnant abdomen under dynamic loading conditions that can occur in crashes. A method has been developed for determining dynamic material properties of human soft tissues that combines results from uniaxial tensile tests, specimen-specific finite-element models based on laser scans that accurately capture non-uniform tissue-specimen geometry, and optimization techniques. The current study applies this method to characterizing material properties of placental tissue. For 21 placenta specimens tested at a strain rate of 12/s, the mean failure strain is 0.472±0.097 and the mean failure stress is 34.80±12.62 kPa. A first-order Ogden material model with ground-state shear modulus (μ) of 23.97±5.52 kPa and exponent (α1) of 3.66±1.90 best fits the test results. The new method provides a nearly 40% error reduction (p<0.001) compared to traditional curve-fitting methods by considering detailed specimen geometry, loading conditions, and dynamic effects from high-speed loading. The proposed method can be applied to determine mechanical properties of other soft biological tissues.

Keywords: Placental abruption

Based on the Corticosteroid Randomisation after Significant Head Injury (CRASH) trial database, a prognosis calculator has been developed for the prediction of outcome in an individual patient with a head injury. In 47 patients with severe traumatic brain injury (sTBI) prospectively treated using an intracranial pressure (ICP) targeted therapy, the individual prognosis for mortality at 14 days and unfavourable outcome at 6 months was calculated and compared with the actual outcome. An overestimation of the risk of mortality and unfavourable outcome was found. The mean risk for mortality and unfavourable outcome were estimated to be 44.6 ± 32.5% (95% confidence interval [CI], 35.1–54.2%) and 69.3 ± 23.7% (95% CI, 62.3–76.2%). The actual outcome was 4.3% and 42.6% respectively. The absolute risk reduction (ARR) for mortality was 33.1% and for unfavourable outcome 29.8%. A logistic fit for outcome at 6 months shows a statistically significant difference (p < 0.01). A receiver operating characteristic (ROC) curve analysis shows an area under the curve (AUC) of 0.691. The {CRASH} prognosis calculator overestimates the risk of mortality and unfavourable outcome in patients with sTBI treated with an ICP-targeted therapy based on the Lund concept. We do not advocate the use of the calculator for treatment decisions in individual patients. We further conclude that patients with blunt sTBI admitted within 8 hours of trauma should be treated regardless of their clinical status as long as the initial cerebral perfusion pressure is >10 mmHg.

Keywords: {CRASH} calculator

The project crashing analysis is to minimize the required cost while meeting a specified deadline. In practice, this problem may be of great complexity because industrial professionals often encounter nonlinear, discrete, or even piecewise discontinuous activity time–cost functions. To handle such complexity and provide enough flexibility, the present study develops and tests a particle swarm optimization (PSO) algorithm to aid in the project crashing analysis. The optimization results include direct and project cost curves, both of which can assist project managers in performing what-if analyses on the project deadline and budget. The application of the proposed algorithm is demonstrated through an example project and a real-life case. The results illustrate the promising performance of the proposed algorithm. Insights are also given to the influence of algorithm parameters.

Keywords: Time

Considerable research has been carried out in recent years to establish relationships between crashes and traffic flow, geometric infrastructure characteristics and environmental factors for two-lane rural roads. Crash-prediction models focused on multilane rural roads, however, have rarely been investigated. In addition, most research has paid but little attention to the safety effects of variables such as stopping sight distance and pavement surface characteristics. Moreover, the statistical approaches have generally included Poisson and Negative Binomial regression models, whilst Negative Multinomial regression model has been used to a lesser extent. Finally, as far as the authors are aware, prediction models involving all the above-mentioned factors have still not been developed in Italy for multilane roads, such as motorways. Thus, in this paper crash-prediction models for a four-lane median-divided Italian motorway were set up on the basis of accident data observed during a 5-year monitoring period extending between 1999 and 2003. The Poisson, Negative Binomial and Negative Multinomial regression models, applied separately to tangents and curves, were used to model the frequency of accident occurrence. Model parameters were estimated by the Maximum Likelihood Method, and the Generalized Likelihood Ratio Test was applied to detect the significant variables to be included in the model equation. Goodness-of-fit was measured by means of both the explained fraction of total variation and the explained fraction of systematic variation. The Cumulative Residuals Method was also used to test the adequacy of a regression model throughout the range of each variable. The candidate set of explanatory variables was: length (L), curvature (1/R), annual average daily traffic (AADT), sight distance (SD), side friction coefficient (SFC), longitudinal slope (LS) and the presence of a junction (J). Separate prediction models for total crashes and for fatal and injury crashes only were considered. For curves it is shown that significant variables are L, 1/R and AADT, whereas for tangents they are L, {AADT} and junctions. The effect of rain precipitation was analysed on the basis of hourly rainfall data and assumptions about drying time. It is shown that a wet pavement significantly increases the number of crashes. The models developed in this paper for Italian motorways appear to be useful for many applications such as the detection of critical factors, the estimation of accident reduction due to infrastructure and pavement improvement, and the predictions of accidents counts when comparing different design options. Thus this research may represent a point of reference for engineers in adjusting or designing multilane roads.

Keywords: Crash-prediction model

Abstract This paper provides strength and durability test results for rubberized concrete that contains silica fume (microsilica) for road side barriers with the intent to reduce injuries and fatalities during crashes. The test program involved the preparation of normal and high strength concretes made out of recycled waste tire rubber. The high strength was obtained by adding silica fume which enhanced the interfacial transition zone bonding. Tire rubber particles composed of a combination of crumb rubber and fine rubber powder were used to replace 10%, 20%, 30%, and 40%, of the total weight of the fine mineral aggregate. The fresh rubberized concrete exhibited lower unit weight and acceptable workability compared to plain concrete. The results of the uniaxial compressive and flexural tests conducted on hardened concrete specimens indicated considerable reductions in axial strength, flexural strength, and tangential modulus of elasticity. Cube Drop tests were performed and showed good resilience of the rubberized concrete. New design guidelines in accordance with the Australian Bridge Design Code {AS} 5100 for strength and serviceability of rubberized concrete road side barriers were derived based on the test results. New moment–thrust interaction curves and shear strength equations were derived for the rubberized concrete road side barriers. The newly derived design rules showed that shear strength is critical compared to the combined moment and axial thrust and the maximum rubber contents were 17% and 30% for normal and high strength concretes, respectively.

Keywords: Concrete

Approximately 48% of all fatal collisions in Europe are classified as single-vehicle run-off-road or head-on collisions. These crashes relate to trajectory control (road departure) and represent a safety challenge. In France, single-vehicle run-off-road crashes represent 21% of all crashes and head-on collisions represent 11%. This study evaluated the effectiveness of four perceptual treatments (i.e., a painted center line, post-delineators, rumble strips on both sides of the center line and sealed shoulders) in supporting the driver to maintain lateral control; that is, to support the driver to keep in the center of his/her lane. Forty-three participants drove a fixed-base driving simulator, on a simulated straight 3 km rural road with two crest vertical curves (CVC). Four sections were chosen for analysis: a reference section (i.e., the first CVC), a test section (i.e., the second CVC), a pre-test section (i.e., immediately before the second CVC) and a post-test section (i.e., immediately after the second CVC). The results showed that drivers drive more at the center of their lane with the rumble strips on both sides of the center line and with the sealed shoulders than with the actual marking (here center line) or other treatments.

Keywords: Driving simulator

Numerical simulations were carried with ABAQUS/Explicit finite element code in order to predict the response of {BWR} Mark {III} type nuclear containment against Boeing 707-320 aircraft crash. The load of the aircraft was applied using Riera (1968) and Riera et al. (1982) force history curve. The damaged plasticity model was used to predict the behavior of concrete while the Johnson–Cook elasto-viscoplastic material model was used to incorporate the behavior of steel reinforcement. The crash was considered to occur at two different locations i.e., the midpoint of the cylindrical portion and the junction of dome and cylinder. The midpoint of the cylindrical portion experienced more deformation. The strain rate in the material model was varied and found to have a significant effect on the response of containment. The results of the present investigation were compared with those of the studies available in literature and a close agreement with the previous results was found in terms of maximum target deformation.

Study objective This study examines whether serum levels of glial fibrillary acidic protein breakdown products (GFAP-BDP) are elevated in patients with mild and moderate traumatic brain injury compared with controls and whether they are associated with traumatic intracranial lesions on computed tomography (CT) scan (positive {CT} result) and with having a neurosurgical intervention. Methods This prospective cohort study enrolled adult patients presenting to 3 Level I trauma centers after blunt head trauma with loss of consciousness, amnesia, or disorientation and a Glasgow Coma Scale (GCS) score of 9 to 15. Control groups included normal uninjured controls and trauma controls presenting to the emergency department with orthopedic injuries or a motor vehicle crash without traumatic brain injury. Blood samples were obtained in all patients within 4 hours of injury and measured by enzyme-linked immunosorbent assay for GFAP-BDP (nanograms/milliliter). Results Of the 307 patients enrolled, 108 were patients with traumatic brain injury (97 with {GCS} score 13 to 15 and 11 with {GCS} score 9 to 12) and 199 were controls (176 normal controls and 16 motor vehicle crash controls and 7 orthopedic controls). Receiver operating characteristic curves demonstrated that early GFAP-BDP levels were able to distinguish patients with traumatic brain injury from uninjured controls with an area under the curve of 0.90 (95% confidence interval [CI] 0.86 to 0.94) and differentiated traumatic brain injury with a {GCS} score of 15 with an area under the curve of 0.88 (95% {CI} 0.82 to 0.93). Thirty-two patients with traumatic brain injury (30%) had lesions on CT. The area under these curves for discriminating patients with {CT} lesions versus those without {CT} lesions was 0.79 (95% {CI} 0.69 to 0.89). Moreover, the receiver operating characteristic curve for distinguishing neurosurgical intervention from no neurosurgical intervention yielded an area under the curve of 0.87 (95% {CI} 0.77 to 0.96). Conclusion GFAP-BDP is detectable in serum within an hour of injury and is associated with measures of injury severity, including the {GCS} score, {CT} lesions, and neurosurgical intervention. Further study is required to validate these findings before clinical application.

Abstract Craniovertebral ligaments were tested to failure under tensile loading. Ligaments tested included: transverse ligament, anterior atlanto occipital membrane, posterior atlanto occipital membrane, capsular ligaments between Skull–C1 and C1–C2, anterior atlantoaxial membrane, posterior atlantoaxial membrane and the tectorial membrane/vertical cruciate/apical/alar ligament complex. The objective of this study was to obtain mechanical properties of craniovertebral ligaments of a younger population, at varying strain rates representative of automotive crash scenarios, and investigate rate and gender effects for use in numerical models of the cervical spine. There have been few studies conducted on the mechanical properties of human craniovertebral ligaments. Only one study has tested all of the ligaments, and previous studies use older age specimens (mean age 67, from most complete study). Further, tests were often not performed at elongation rates representative of car crash scenarios. Previous studies did not perform tests in an environment resembling in vivo conditions, which has been shown to have a significant effect on ligament tensile behaviour. Fifty-four craniovertebral ligaments were isolated from twenty-one spines, and tested to failure in tension under simulated in vivo temperature and hydration levels, at quasi-static (0.5 s−1) and high strain rates (150 s−1). Values for failure force, failure elongation, stiffness, and toe region elongation were obtained from force–displacement curves. Values were analyzed for strain rate and gender effects. Increased strain rate produced several significant effects including: higher failure forces for the transverse ligament and capsular ligament (Skull–C1), lower failure elongation for the tectorial membrane complex, higher stiffness for the tectorial membrane complex and capsular ligament (Skull–C1), and lower toe region elongation for capsular ligament (Skull–C1). Gender effects were limited. Ligament tests demonstrated expected rate effects. Younger specimens had a higher failure force and stiffness and failed at lower elongations than older specimens from previous studies. Gender effects suggest there may be a difference between male and female properties, but require further testing to establish greater significance.

Keywords: Cervical spine

Abstract Many victims in traffic accidents do not receive optimal care due to the fact that the severity of their injuries is not realized early on. Triage protocols are based on physiological and anatomical criteria and subsequently on mechanisms of injury in order to reduce undertriage. In this study the value of accident characteristics for field triage is evaluated by developing an on scene injury severity prediction (OSISP) algorithm using only accident characteristics that are feasible to assess at the scene of accident. A multivariate logistic regression model is constructed to assess the probability of a car occupant being severely injured following a crash, based on the Swedish Traffic Accident Data Acquisition (STRADA) database. Accidents involving adult occupants for calendar years 2003–2013 included in both police and hospital records, with no missing data for any of the model variables, were included. The total number of subjects was 29 128, who were involved in 22 607 accidents. Partition between severe and non-severe injury was done using the Injury Severity Score (ISS) with two thresholds: {ISS} > 8 and {ISS} > 15. The model variables are: belt use, airbag deployment, posted speed limit, type of accident, location of accident, elderly occupant (>55 years old), sex and occupant seat position. The area under the receiver operator characteristic curve (AUC) is 0.78 and 0.83 for {ISS} > 8 and {ISS} > 15, respectively, as estimated by 10-fold cross-validation. Belt use is the strongest predictor followed by type of accident. Posted speed limit, age and accident location contribute substantially to increase model accuracy, whereas sex and airbag deployment contribute to a smaller extent and seat position is of limited value. These findings can be used to refine triage protocols used in Sweden and possibly other countries with similar traffic environments.

Keywords: Triage

Purpose: To evaluate agreement between police and trained investigators regarding seat belt use by crash victims, according to injury severity. Methods: We used data from the National Accident Sampling System Crashworthiness Data System (CDS) for front seat occupants, 16 years and older, in crashes during 1993–2000. Crashworthiness Data System investigators determined belt use from vehicle inspection, interviews, and medical record information; their assessment was considered the gold standard for this analysis. Occupant severity of injury was categorized in five levels from no injuries to death. We estimated the sensitivity, specificity, and area under receiver operating characteristic curves for police reports of belt use. Results: Among 48,858 occupants, sensitivity of a police report that a belt was used was 95.8% overall and varied only modestly by injury severity. Specificity of a police report that a belt was not used was 69.1% overall; it was the lowest among the uninjured (53.2%) and greatest among the dead (90.4%). The area under the curve was 0.82 (95% confidence interval 0.82–0.83) overall; this was lowest among those not injured (0.75, 95% confidence interval 0.74–0.76) and increased with injury severity to 0.91 (95% confidence interval 0.90–0.93) among those who died. Conclusion: Police usually classify belted crash victims as belted, regardless of injury severity. But they often classify unbelted survivors as belted when they were not. This misclassification may result in exaggerated estimates of seat belt effectiveness in some studies.

Keywords: Seat belts

The response of a boiling water reactor (BWR) nuclear containment vessel has been studied against commercial and fighter aircraft crash using a nonlinear finite element code ABAQUS. The aircrafts employed were Boeing 747-400, Boeing 767-400, Airbus A-320, Boeing 707-320 and Phantom F4. The containment was modeled as a three-dimensional deformable reinforced concrete structure while the loading of aircraft was assigned using the respective reaction–time curve. The location of strike was considered near the junction of dome and cylinder, and the angle of incidence, normal to the containment surface. The material behavior of the concrete was incorporated using the damaged plasticity model while that of the reinforcement, the Johnson–Cook elasto-viscoplastic model. The containment could not sustain the impact of Boeing 747-400 and Boeing 767-400 aircrafts and suffered rupture of concrete around the impact region leading to global failure. On the other hand, the maximum local deformation at the point of impact was found to be 0.998 m, 0.099 m, 0.092 m, 0.089 m, and 0.074 m against Boeing 747-400, Phantom F4, Boeing 767, Boeing 707-320 and Airbus A-320 aircrafts respectively. The results of the present study were compared with those of the previous analytical and numerical investigations with respect to the maximum deformation and overall behavior of the containment.

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.

Keywords: Heterogeneity-in-means

Vehicular cyber physical system (VCPS) can comprehensively acquire road traffic safety related information, and provide drivers with early warning or driving assistance in emergency, in order to assist them avoid vehicle crash in the driving process. Literature review shows that previous studies mainly rely on observed vehicle motion/location data for assessing vehicle collision risk, where predicted vehicle motion/location, driver behavior and road geometry (e.g., curvature) are rarely considered. In this study, based on the simulated VCPS, a collision avoidance system that can explicitly consider the above issues is designed and presented in detail. Within the proposed collision avoidance system, an assessment method, which can predict collision risk by comprehensively considering vehicles motion/location, driver behavior and road geometry information from the VCPS, is developed. Firstly, the short-term motion of the objective vehicle and surrounding vehicles are predicted based on the Kalman Filter (KF) algorithm and the vehicle motion model. Furthermore, the proposed method that can explicitly take driver behavior and road curvature into account is used to predict vehicle location and calculate the traveled distance among vehicles in real-time. Then, the predicted vehicle gaps are compared with a safe distance threshold and the vehicle collision risk is predicted. Finally, the accuracy of the proposed collision risk assessment method is examined with a receiver operating characteristic (ROC) curve analysis over a section of curved road. Simulation results show that the proposed method is effective for detecting collision risk and providing accurate warnings in a timely fashion.

Keywords: Collision avoidance

Traffic congestion in modern cities is an increasing problem having significant consequences in our daily lives. This work proposes a non-intrusive, passive monitoring framework based on the acoustic modality which can be used either autonomously or as a part of a multimodal system and provide valuable information to an intelligent transportation system. We consider a large number of audio classes which are typically encountered in urban areas. We introduce a combination of a powerful audio representation mechanism based on time, frequency and wavelet domain features with universal background modeling which leads to higher recognition accuracies and detection rates (in terms of false alarm and miss probability rates) with respect to commonly employed methodologies. The basic advantage of a class-specific model derived using the universal background modeling logic is its tolerance to data which belong to other sound classes. Another important feature of the proposed system is its ability to detect crash incidents, which apart from their catastrophic impact on human life and property, have negative consequences on the traffic flow. Our experiments are based on the concurrent usage of professional sound effect collections which include audio recordings of high quality. We thoroughly examine the performance of the proposed system on isolated sound events as well as continuous audio streams using confusion matrices and detection error trade-off curves.

Keywords: Acoustic signal processing

Lower limbs are normally the first contacted body region during car–pedestrian accidents, and easily suffer serious injuries. The previous tibia bending tolerances for pedestrian safety were mainly developed from three-point bending tests on tibia mid-shaft. The tibia tolerances of other locations are still not investigated enough. In addition, tibia loading condition under the car–pedestrian impact should be explored to compare with the three-point bending. This work aims to investigate the injury tolerance of tibia fracture with combined experimental data and numerical simulation. Eleven new reported quasi-static bending tests of tibia mid-shaft, and additional eleven dynamic mid-shaft bending test results in the previous literature were used to define injury risk functions. Furthermore, to investigate the influence of tibia locations on bending tolerance, finite element simulations with lower limb model were implemented according to three-point bending and pedestrian impact conditions. The regressive curve of tibia bending tolerance was obtained from the simulations on the different impact locations, and indicated that tibia fracture tolerance could vary largely due to the impact locations for the car–pedestrian crash.

Keywords: Finite element modeling

Summary This study assessed the current secular trends in unintentional injury deaths among persons 15 years of age or older in Finland. For this purpose, we obtained from the Finnish Official Cause-of-Death Statistics (OCDS) the data for persons aged 15 years or older whose deaths occurred in 1971–2003 due to an unintentional injury. Among Finnish men, the most drastic change occurred in road traffic crashes. The age-standardised death rate (per 100,000 person-years) of men's road traffic crashes was 47 in 1971 but only 11 in 2003. In contrast, the rate of fall-induced deaths among Finnish men gradually rose, from 18 in 1971 to 24 in 2003, by which time falls became the leading category of men's unintentional injury death. Also alcohol poisonings seemed to bypass road traffic crashes as the cause of men's injury death. Among Finnish women, the age-standardised rate of fall-induced deaths decreased till 1975, after which the curve was rather flat. The death rate (per 100,000 person-years) of women's falls was 30 in 1971 and 18 in 2003. During the entire period of 1971–2003, traffic caused fewer deaths in women than men, but the declining trend in women's death rates was also clear, from 17 in 1971 to 5 in 2003. Other unintentional causes accounted for few deaths in women during 1971–2003, although it was of interest that the rate of women's deaths due to alcohol poisoning rose from 1 in 1971 to 4 in 2003. In conclusion, during1971–2003 falls replaced road traffic crashes as the leading cause of unintentional injury death in adult Finns. The rise in men's fall-induced deaths occurred even with a rate that cannot be explained merely by demographic changes, and therefore, systematic fall prevention measures are needed to control the development. The rising incidence of women's deaths due to alcohol poisoning needs close follow-up.

Keywords: Adult Finns

An airbag is composed of a housing assembly, door assembly, cushion assembly, and an inflator. The inflator is an essential part that generates gas for the airbag. When an airbag is activated, it effectively absorbs the crash energy of the passenger by inflating a cushion. In the present study, tank tests were performed with newly synthesized propellants with various compositions, and the results are compared with the numerical results. In the simulation of the inflator, a zonal model has been adopted which consisted of four zones of flow regions: combustion chamber, filter, gas plenum, and discharge tank. Each zone was described by the conservation equations with specified constitutive relations for gas. The pressure and temperature of each zone of the inflator were calculated and analyzed, and the results were compared with the tank test data. The similarity of the pressure curve and closed bomb calculation show that the modeled results are well correlated with the experimental data.

Keywords: Propellant

Introduction Induced exposure has a long history of development and usage in traffic safety research but a major question has always concerned the extent to which the accumulation of culpable and non-culpable involvements can be considered independent. Method Culpability assessments of 32,630 vehicles' crash-claim involvements adjudicated by insurance adjusters were matched with vehicle odometer readings taken at emission testing using consistent identification of vehicles and principal operators over a 5-year period. Result It was found that the accumulation of culpable crash involvements was not entirely independent of that for non-culpable involvements. However, the rate of non-culpable involvements was determined to be an acceptable surrogate for travel exposure rate where sample sizes were large. Discussion The relationship between the rate of non-culpable involvements and the rate of travel exposure for data subsets when both were normalized by the overall sample rates was reminiscent of an accident-volume curve for roadway locations in traffic engineering theory. This suggested that only a portion of non-culpable involvements actually related directly to travel and this lead to a correction factor that could be applied. Impact on Industry While lack of independence of involvement rates may be problematic for a direct risk ratio application, it does not invalidate the use of non-culpable involvements to predict travel. For insurers that have a need to estimate travel amounts for different driver/vehicle groups as part of the insurance rating purposes, this can be a useful application.

Keywords: Travel

To develop a scoring tool based on clinical and radiological findings for early diagnosis and intervention in hemodynamically stable patients with traumatic bowel and mesenteric injury (TBMI) without obvious solid organ injury (SOI). Methods A retrospective analysis was conducted for all traumatic abdominal injury patients in Qatar from 2008 to 2011. Data included demographics and clinical, radiological and operative findings. Multivariate logistic regression was performed to analyze the predictors for the need of therapeutic laparotomy. Results A total of 105 patients met the inclusion criteria with a mean age of 33 ± 15. Motor Vehicle Crashes (58%) and fall (21%) were the major MOI. Using Receiver operating characteristic curve, Z-score of >9 was the cutoff point (AUC = 0.98) for high probability of the presence of {TBMI} requiring surgical intervention. Z-Score >9 was found to have sensitivity (96.7%), specificity (97.4%), {PPV} (93.5%) and {NPV} (98.7%). Multivariate regression analysis found Z-score (>9) to be an independent predictor for the need of exploratory laparotomy (OR7.0; 95% CI: 2.46–19.78, p = 0.001). Conclusion This novel tool for early diagnosis of {TBMI} is found to be simple and helpful in selecting stable patients with free intra-abdominal fluid without {SOI} for exploratory Laparotomy. However, further prospective studies are warranted.

Keywords: Blunt trauma

The reaction between hydrogen and high-sulfur coal at high temperature was investigated. Crashed and sieved high-sulfur coal sample was placed in a 23 mm I.D. differential reactor. The release of hydrogen sulfide at run temperature and under different hydrogen atmospheres was recorded by a hydrogen sulfide detector. Desulfurization yield was obtained through the elemental analysis of residual char. The grain reaction and random pore models were modified to facilitate the description of reaction kinetics characteristics. Hydrogen was observed to promote the desulfurization rate considerably; i.e., more than 65% of sulfur in coal could be removed. The releasing curves of {H2S} in the hydropyrolysis process exhibited two peaks. The desulfurization process in the hydropyrolysis of high-sulfur coal could be regarded as two stages based on the evolution profiles of H2S. The first peak at 250–450 °C was derived from the desulfurization of aliphatic sulfide. The second peak at 450–650 °C was produced from the sulfur in pyrite and aromatic thiophenic structure. The desulfurization of high sulfur could be described more effectively with the grain reaction model than with the random pore model. The random pore model was only adopted in the initial stage of sulfur removal of high-sulfur coal under hydrogen atmosphere. The grain reaction model was adequate for the entire stage.

Keywords: High-sulfur coal

Steel spot-welded hat-type sections are used extensively in the automotive industry to manufacture vehicle structures. The main objective when designing a crashworthy vehicle is to protect the occupants in the event of a collision by dissipating crash energy via large plastic deformation and ensuring the survival space is not encroached. In rollover crashes, the components in the roof structure will be subjected to large deformation bending as the roof frame collapses and kinetic energy is dissipated. This paper presents a procedure whereby the energy absorbed by a spot-welded hat section under large deformation bending may be determined. The results are shown to compare well with experiments of spot-welded hat sections with seven different geometries and four different perforation sizes. The perforations were introduced into the compression flange of the sections. The range of section and perforation geometries investigated was designed to cover the full range typical to the automotive industry. The theoretical large deformation bending moment–rotation curves and energy absorbed are determined from a rigorous yet relatively simple three stage process, which includes elastic, in-plane plastic and plastic collapse mechanism components.

Keywords: Steel hat sections

The rapid advancement in computational power has made human finite element (FE) models one of the most efficient tools for assessing the risk of abdominal injuries in a crash event. In this study, specimen-specific {FE} models were employed to quantify material and failure properties of human liver parenchyma using a {FE} optimization approach. Uniaxial tensile tests were performed on 34 parenchyma coupon specimens prepared from two fresh human livers. Each specimen was tested to failure at one of four loading rates (0.01 s−1, 0.1 s−1, 1 s−1, and 10 s−1) to investigate the effects of rate dependency on the biomechanical and failure response of liver parenchyma. Each test was simulated by prescribing the end displacements of specimen-specific {FE} models based on the corresponding test data. The parameters of a first-order Ogden material model were identified for each specimen by a {FE} optimization approach while simulating the pre-tear loading region. The mean material model parameters were then determined for each loading rate from the characteristic averages of the stress–strain curves, and a stochastic optimization approach was utilized to determine the standard deviations of the material model parameters. A hyperelastic material model using a tabulated formulation for rate effects showed good predictions in terms of tensile material properties of human liver parenchyma. Furthermore, the tissue tearing was numerically simulated using a cohesive zone modeling (CZM) approach. A layer of cohesive elements was added at the failure location, and the {CZM} parameters were identified by fitting the post-tear force–time history recorded in each test. The results show that the proposed approach is able to capture both the biomechanical and failure response, and accurately model the overall force–deflection response of liver parenchyma over a large range of tensile loadings rates.

Keywords: Human liver

This paper deals with the development and application of a new space curved frame finite element to be used for crash analysis (non-linear). The frame finite element has been developed using a mixed variational principle (complementary form) and using rotations as independent variables. The formulation has been validated for problems of large deflection and rotation, and for problems involving initially curved members. Based on the validation performed, it is expected that crash problems may be modelled using a single element per member thus retaining computational efficiency while performing an accurate analysis. An illustrative example (modelling of an S-leg seat) is presented here to illustrate the benefits of the proposed approach to a designer.

Deceleration lanes are important because they help drivers transition from high-speed lanes to low-speed ramps. Although they are designed to allow vehicles to depart the freeway safely and efficiently, many studies report high accident rates on exit ramps with the highest percentage of crashes taking place in deceleration lanes. This paper describes the results of a driving simulator study that focused on driving performance while approaching a divergence area and decelerating during the exiting maneuver. Three different traffic scenarios were simulated to analyze the influence of traffic volume on driving performance. Thirty drivers drove in the simulator in these scenarios while data on their lateral position, speed and deceleration were collected. Our results indicate there are considerable differences between the main assumptions of models generally used to design deceleration lanes and actual driving performance. In particular, diverging drivers begin to decelerate before arriving at the deceleration lane, causing interference with the main flow. Moreover, speeds recorded at the end of the deceleration lane exceed those for which the ramp's curves are designed; this creates risky driving conditions that could explain the high crash rates found in studies of exit ramps. Finally, statistical analyses demonstrate significant influences of traffic volume on some aspects of exiting drivers’ performance: lower traffic volume results in elevated exiting speed and deceleration, and diverging drivers begin to decelerate earlier along the main lane when traffic volume is low. However, speeds at the end of the deceleration lane and the site of lane changing are not significantly influenced by traffic volume.

Keywords: Driving simulator

The controlling plastic deformation mechanisms (i.e. slip or twinning) and the structural crash performance of Mg alloys are strongly influenced by loading mode, texture and microstructure. This paper summarizes the main results from an experimental program to assess these effects for commercial Mg alloy extrusions (AM30 and AZ31), sheet (AZ31), and high pressure die castings (HPDC, {AM50} and AM60). Uniaxial tensile and compressive tests were performed over a wide range of strain rate and temperature (i.e. 0.00075–2800 s−1 and 100 °C to −150 °C) using conventional servo-hydraulic and high-strain-rate universal test machines and a split-Hopkinson-bar (SHB) apparatus. In primarily-slip-dominant deformation, the true stress–strain curves showed approximate power-law behavior, and the effects of strain rate and temperature on yield strength could be approximately described by constitutive equations linearly dependent on the rate parameter, T ln ( 5.3 × 10 7 / ɛ ˙ ) where T is test temperature in Kelvin and ɛ ˙ is strain rate in s−1. In primarily-twin-dominant deformation, the effects of strain rate and temperature on yield and initial flow stress were negligible or small from quasi-static to 2800 s−1 owing to the athermal characteristics of mechanical twinning; the effects may become more pronounced with exhaustion of twinning and increasing proportion of slip.

Keywords: Constitutive equation

In a previous study we presented a new method that used summed probability distributions (SPD) of radiocarbon dates as a proxy for population levels, and Monte-Carlo simulation to test the significance of the observed fluctuations in the context of uncertainty in the calibration curve and archaeological sampling. The method allowed us to identify periods of significant short-term population change, caveated with the fact that around 5% of these periods were false positives. In this study we present an improvement to the method by applying a criterion to remove these false positives from both the simulated and observed distributions, resulting in a substantial improvement to both its sensitivity and specificity. We also demonstrate that the method is extremely robust in the face of small sample sizes. Finally we apply this improved method to radiocarbon datasets from 12 European regions, covering the period 8000–4000 BP. As in our previous study, the results reveal a boom-bust pattern for most regions, with population levels rising rapidly after the local arrival of farming, followed by a crash to levels much lower than the peak. The prevalence of this phenomenon, combined with the dissimilarity and lack of synchronicity in the general shapes of the regional SPDs, supports the hypothesis of endogenous causes.

Keywords: Neolithic

The {EC} {CASPER} (Child Advanced Safety Project for European Roads) project aims at decreasing injuries and fatalities of child occupants. This goal represents a major social and economic benefit for the whole European Community. {CASPER} has carried out a two way approach for improving child safety. Results are complementary. Firstly, the improvement of quality of use of restraint systems is certainly a good way for a rapid and consequent improvement of the situation, secondly, it is necessary to give guidelines and reliable tools to design protection devices that are easier to use, have a higher level of crash performance and are used for a large proportion of children. {CASPER} involves a consortium of 15 European partners representing a good balance between industry, medical and technical universities, road state institutes and organizations specialized in road safety issues for a 36 month project. This project was accepted under the {GA} n°218564 of the FP7-SST-2007-RTD-1-program of the European Commision that is partially funding the project. Data from previous European projects were used as a basis. In-depth accident investigations, misuse (incorrect use of a restraint system) and sociological field data collection took place and were analyzed. Existing tools used for the evaluation of protection of children were improved while missing ones were developed. These are used to address issues identified by the field data analysis. In addition to proposals of improvements for the Q-series crash test dummies, further development of injury risk curves both for frontal and side impact is ongoing. Finite element models have been developed for child dummies and for human child bodies. An analysis of test procedures was done in order to define the highest priorities. {CASPER} is now finalizing the tools and proposing solutions that could be applied to improve child safety in cars, whilst evaluating if some of these solutions could be transferred to other transportation modes.

Keywords: Child safety

A crane hanger in a paper factory failed during service, causing the crash of the transported paper spool weighing 10 tons. Fatigue cracking over 1/3 of the cross section was visible, surprisingly starting at the contact point with the crane hook, where the lifted load produces compressive stresses. This counter-intuitive crack origin could be explained by the manufacturing residual stresses, but still not the final fracture of the hanger. The fractography by {SEM} revealed a multi-modal fracture pattern, including a cleavage fast crack region, surprisingly sandwiched between two sections of fatigue cracking. For explanation of this non-intuitive pattern, a residual strength approach has been chosen. For this, the bending moment “M” due to the manufacturing constraints and the corresponding bending resistance “Mc” of the hanger’s critical cross section were determined as a function of the crack length “a”. The function M(a) was computed with a finite element model of the cracked hanger. The function Mc(a) was defined by means of fracture mechanics methodology. The stress intensity model is based upon the existing solution of a shaft in bending, adapted for the curved shape of the hanger’s arch and extended for deep cracks using the compounding technique. In order to find the conditions for on-set and arrest of the crack, the stress intensity was replaced by the fracture toughness of the steel. This material property was estimated using a semi empirical theory, which uses classical mechanical steel properties and accounts for the effect of the thickness and dynamic loading on fracture toughness. The cross points of the obtained M(a) and the Mc(a) curves in the residual strength diagram correlate well with the observed crack lengths both at on-set and at arrest of brittle fast cracking between phases of fatigue cracking. This consistency indicates the general suitability of the proposed fracture mechanics model.

Keywords: Fracture mechanics

To assist in the on-going effort to reduce road fatalities as much as possible, this paper presents a new methodology to evaluate road safety in both the design and redesign stages of two-lane rural highways. This methodology is based on the analysis of road geometric design consistency, a value which will be a surrogate measure of the safety level of the two-lane rural road segment. The consistency model presented in this paper is based on the consideration of continuous operating speed profiles. The models used for their construction were obtained by using an innovative GPS-data collection method that is based on continuous operating speed profiles recorded from individual drivers. This new methodology allowed the researchers to observe the actual behavior of drivers and to develop more accurate operating speed models than was previously possible with spot-speed data collection, thereby enabling a more accurate approximation to the real phenomenon and thus a better consistency measurement. Operating speed profiles were built for 33 Spanish two-lane rural road segments, and several consistency measurements based on the global and local operating speed were checked. The final consistency model takes into account not only the global dispersion of the operating speed, but also some indexes that consider both local speed decelerations and speeds over posted speeds as well. For the development of the consistency model, the crash frequency for each study site was considered, which allowed estimating the number of crashes on a road segment by means of the calculation of its geometric design consistency. Consequently, the presented consistency evaluation method is a promising innovative tool that can be used as a surrogate measure to estimate the safety of a road segment.

Keywords: Road safety

In near-field optics, the use of vertical vibration of the probe is of great interest in order to prevent the tip crash, in tapping mode. The optical signal is often obtained through a lock-in amplifier using a feedback on this vertical vibration. Therefore, harmonics of the optical signal are available. The reconstruction of the near-field signal, from these harmonics, enables the knowledge of the vertical variations of the near-field signal, without the use of the slower technique of approach curves or the use of photocounter. In this work, we use this reconstruction to measure the vertical decay lengths of the near-field data with the Prony’s and the simplex methods. We compare both methods and we discuss the results in terms of filtering by the lock-in.

Keywords: Image forming and processing

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.

Keywords: Age

National data were analyzed to define the nature and importance of the problem of ran-off-road vehicles that rollover on slopes and ditches. Also, data from two specialized data bases were used to obtain insight on vehicle orientation and driver maneuvers in such crashes. This crash type was found to be the leading cause of ran-off-road driver fatalities, accounting for about one-fourth of this total. Highway factors associated with this crash type are identified to assist in the effort to define specific roadway locations where highway design countermeasures may be appropriate. Specifically, attention should be given to the outside of horizontal curves on rural two-lane roads. Vehicle dynamics computer simulations appear to offer the most promising approach to obtain needed insight on rollover risks for specific slope and ditch geometric combinations. Vehicle trajectory information found in this study should be useful in the design and interpretation of needed follow-on simulation studies. Vehicle trajectories in slope rollovers were found to be both different from, and more complex than, fixed object crashes.

Keywords: Rollover

Thoracic injuries are a major cause of mortality in frontal collisions, especially for elderly and obese people. Car occupant individual characteristics like {BMI} are known to influence human vulnerability in crashes. In the present study, thoracic mechanical response of volunteers quantified by optical method was linked to individual characteristics. 13 relaxed volunteers of different anthropometries, genders and age were submitted to non-injurious sled tests (4 g, 8 km/h) with a sled buck representing the environment of a front passenger restrained by a 3-point belt. A resulting shoulder belt force was computed using the external and internal shoulder belt loads and considering shoulder belt geometry. The mid sternal deflection was calculated as the distance variation between markers placed at mid-sternum and the 7th vertebra spinous process of the subject. Force-deflection curves were constructed using resulting shoulder belt force and midsternal deflection. Average maximum chest compression was 7.9±2.3% and no significant difference was observed between overweight subjects (BMI≥25 kg/m²) and normal subject (BMI<25 kg/m²). The overweight subjects exhibited significantly greater resultant belt forces than normal subjects (715±132 N vs. 527±111 N, p<0.05), higher effective stiffness (30.9±10.6 N/mm vs. 19.6±8.9 N/mm, p<0.05) and lower dynamic stiffness (42.7±8.71 N/mm vs. 61.7±15.5 N/mm, p<0.05).

Keywords: Biomechanics

The present paper discusses significant design issues in the sizing of rotorcraft structures for requirements of enhanced crash performance. The focus of the study is on topological design of the subfloor structure, defined as a crush zone under a more rigid floor structure. The topological design problem includes both an appropriate selection of an energy absorbing material (tailored load-deflection curve), and placement of this material at discrete locations under the main floor structure. A genetic algorithm based optimization approach was used in conjunction with a crash response analysis code (KRASH), which uses lumped masses, linear and nonlinear beam elements, and nonlinear spring elements to model the primary and secondary structure. The analysis problem is computationally demanding, and to alleviate these costs, approximate response models based on a multilayer perceptron neural network were developed and used in the optimization studies.

The objective of this study was to calculate the potential effectiveness of a pedestrian injury mitigation system that autonomously brakes the car prior to impact. The effectiveness was measured by the reduction of fatally and severely injured pedestrians. The database from the German In-Depth Accident Study (GIDAS) was queried for pedestrians hit by the front of cars from 1999 to 2007. Case by case information on vehicle and pedestrian velocities and trajectories were analysed to estimate the field of view needed for a vehicle-based sensor to detect the pedestrians one second prior to the crash. The pre-impact braking system was assumed to activate the brakes one second prior to crash and to provide a braking deceleration up to the limit of the road surface conditions, but never to exceed 0.6 g. New impact speeds were then calculated for pedestrians that would have been detected by the sensor. These calculations assumed that all pedestrians who were within a given field of view but not obstructed by surrounding objects would be detected. The changes in fatality and severe injury risks were quantified using risk curves derived by logistic regression of the accident data. Summing the risks for all pedestrians, relationships between mitigation effectiveness, sensor field of view, braking initiation time, and deceleration were established. The study documents that the effectiveness at reducing fatally (severely) injured pedestrians in frontal collisions with cars reached 40% (27%) at a field of view of 40°. Increasing the field of view further led to only marginal improvements in effectiveness.

Keywords: Pedestrian

A conceptual, continuous, daily, semi distributed catchment-scale rainfall-runoff model that has the potential to be ultimately used in ungauged catchments is described. The Catchment Resources and Soil Hydrology (CRASH) model is developed from the basis that the transformation of rainfall into simulated river discharge can be parameterised using pre-existing national datasets of soil, land use and weather; and that the spatial variability in soil properties and land use are important to the hydrological response of a catchment and should be incorporated into the catchment representation. Both infiltration-excess and saturation-excess runoff mechanisms are simulated, with water movement through each soil layer simulated using a capacitance approach limited according to layer physical properties. The hydrological linkage between the response unit and catchment is parameterised using the existing national Hydrology of Soil Types (HOST) classification. The {HOST} classification groups all {UK} soil types into one of 29 hydrological classes for which nationally calibrated values of Base Flow Index and Standard Percentage Runoff are provided. {CRASH} has been calibrated and validated for three catchments in England with contrasting soil characteristics and meteorological conditions. The model was successful at simulating time series and flow duration curves in all catchments during the calibration and validation periods. The next development stage will be to test {CRASH} for a large number of catchments covering a wider range of soils, land uses and meteorological conditions, in order to derive a set of regionalised model parameters based upon the {HOST} classification. The successful cross-scale linkage between water movement through the response unit and the catchment-scale hydrological response using the {HOST} classification, which incorporates the scale effects between plot and catchment, suggests that such national soil hydrological classifications may provide a sound and consistent framework for hydrological modelling in both gauged and ungauged catchments which should be extended to other regions.

Keywords: Rainfall-runoff model

A phenomenological constitutive model is represented to describe the flow behavior of metals over wide ranges of strain rates and temperatures. The novelties of proposed elasto-plastic model are: (a) precisely can predict yield stress and flow curve shape in various strain rate as both yield stress and back stress are attached with different strain rate dependent functions, (b) ability to calculate the energy absorbed during crash event as it can track stress–strain behavior correctly beyond uniform elongation. Determination of eight material constants for proposed model from experimental data is very simple and straight forward. The model predictions show a very good agreement with experimental results obtained from the literatures for a wide range of strain rates and temperatures for different steels (mild steel ES, {DP600} and {TRIP700} steels).

Keywords: High strain rate

Too much has been written about forecasting trends via “envelope curves.” To plot a straight line on log-paper is a no-brainer. The special phenomenology of phase changes, catastrophes, or “crashes,” and their key evolutionary role is the subject of this article. There is no unique way of forecasting such events, but one indicator is an apparent inconsistency between two or more extrapolations with each other. Alternatively, a catastrophe may be signalled when a trend extrapolation encounters a natural limit. A number of possible discontinuity scenarios are sketched, although overall, the article laments the lack of theorization in forecasting disconuities.

{ACL2} is the latest inception of the Boyer-Moore theorem prover, the 2005 recipient of the {ACM} Software System Award. In the hands of experts it feels like a finely tuned race car, and it has been used to prove some of the most complex theorems ever proved about commercially designed systems. Unfortunately, {ACL2} has a steep learning curve. Thus, novices tend have a very different experience: they crash and burn. As part of a project to make {ACL2} and formal reasoning safe for the masses, we have developed ACL2s, the {ACL2} sedan. {ACL2s} includes many features for streamlining the learning process that are not found in ACL2. In general, the goal is to develop a tool that is “self-teaching,” i.e., it should be possible for an undergraduate to sit down and play with it and learn how to program in {ACL2} and how to reason about the programs she writes.

Keywords: ACL2

Developing spatially resolved high-resolution datasets of robust long-term changes in human demography constitutes a major challenge for archaeology. One approach is to use the distribution of summed radiocarbon-age probabilities to infer long-term population dynamics (i.e. palaeodemography). However, these can often be biased by preservation potential, site taphonomy or researcher priorities among other aspects, all of which require large datasets to resolve adequately. For this report, we have created such a dataset for the South-Central Andes (16°–25°S), here termed the South Central Andes Radiocarbon (SCAR) database. {SCAR} spans the last 15,000 years and incorporates ∼1700 14C-dates from 519 archeological sites reported across an extreme bioclimatic gradient that includes the hyperarid coastal Atacama Desert and adjacent cold, high-elevation Altiplano. Among the possible methodological biases, we first evaluated those related to calibration procedures. Otherwise, changes in summed probability curves show no other relevant biases except for possible research interest/priorities that could be responsible for the gaps in the record from the Bolivian altiplano. Our temporally continuous time-series indicates that prehispanic populations exhibited significant demographic changes during the last 13,100 cal BP. Except for coastal populations; most regions show strongly coordinated demographic fluctuations that follow the same major patterns. Thus, we identified two broad scale population events across the South-Central Andes (Atacama inland, Bolivian Altiplano) from 13,100–4000 cal {BP} and then from 4000 cal {BP} to the present. In contrast, the Atacama coastal records suggest a different and more variable occupation pattern over the last 13,460 cal BP, which could be driven by the interaction with oceanographic processes (i.e. upwelling). A widespread major decline at 700 cal {BP} clearly predates the Spanish colonization and occurs in all of our regions. This widespread decline does not appear to be due to methodological biases, and suggests that a population crash occurred before European occupation. Overall, the {SCAR} database constitutes a valuable proxy for establishing the long-term dynamics of prehistoric societies that inhabited the western Andean slope. Time-series analyses that use {SCAR} will shed new light on the demographic and cultural dynamics at different spatial-scales, and help clarify the processes involved in the migrational trajectories and cultural evolution of the peoples that inhabited the South-Central Andes over the last 15,000 years.

Keywords: Summed probabilities

Cellular materials such as aluminium honeycombs combine lightweight with an efficient crash energy absorption capability. They have a major role in a wide range of transport applications to reduce gas emission by the design of lighter structures but remaining safe in accident case. Many investigations on the honeycomb behaviour have been performed, under uni-axial compression loading and more recently under mixed shear–compression loading. The influence of the in-plane orientation has not been however considered. The objective is to develop a reduced numerical model able to investigate, with a reduced cost of calculations, the dynamic behaviour of honeycomb under mixed shear–compression loading and taking into account of the in-plane orientation angle. Reduced model based on the periodicity procedure is developed and its validity range is evaluated. The numerical results show that in terms of pressure–crush curve and collapse mechanisms, the reduced model is consistent with a complete {FE} model composed of 39 cells with a CPU-time gain efficiency about 97.17%. The reduced model is valid from a loading angle ψ = 0 ° to a loading angle ψ limit contained between ψ = 30 ° and ψ = 45 ° . The reduced model allows investigating in depth the influence of the in-plane orientation and the loading angles on the crush behaviour with minimum time calculations in accord with the validity range.

Keywords: Honeycomb

The simulation of ductile fracture in real components is becoming a strategic issue in numerical simulations. Numerical simulations of crashes, forming processes, impacts and fractures are reliable only if carried out with an accurate material calibration. The topics involved in this kind of simulation require a complete calibration of both the true stress–strain curve and the failure. The focus of this work is the accurate calibration of the constitutive relations of the titanium alloy Ti–6Al–4V. The approach proposed is based on different experimental tests supported by numerical simulations performed by means of detailed {FE} models. The Bao–Wierzbicki ductile failure criterion is calibrated using a total of 11 specimens. These specimens are tested on a multiaxial test machine to investigate the failure at different stress triaxialities. Furthermore, the sensitivity to the mesh size and the assessment of the calibration accuracy are analysed in detail on different components in order to verify the geometry transferability.

Keywords: Material calibration

A raw material grinding circuit was modeled using plant data. Samples were collected from around the circuit and, following a crash stop, from inside the mill. The size distributions of the samples were determined down to a few microns. Using the data from inside the mill a modeling approach, based on perfect mixing, was developed. The modelling approach implicitly assumes that the mixture of feed materials broken is homogenous from the breakage point of view. The air classification around the circuit was modeled using the efficiency curve approach. In order to measure the success of the method the circuit performance was predicted by simulation studies while it was operating at different conditions. The results were then compared with the measured data. It is concluded that modeling gives a useful quantitative indication of what may occur in fully air swept mills.

Keywords: Cement

Magnesium alloys are an ideal candidate due to their low density in comparison to aluminum and steel alloys when designing a vehicle with lower weight and therefore, reduced fuel consumption. It is important to characterize the strain rate sensitivity of any material that will be used in a structure which can undergo high rate deformation (as in an automobile crash) as well as during high velocity forming processes such as electromagnetic or electrohydraulic forming. Tensile tests for {AZ31B} magnesium alloy sheet at different strain rates were carried out using different testing techniques: (i) quasi-static strain rates tests were conducted in a range between 10−3 and 10−1 s−1 using a conventional electro-mechanical tensile testing apparatus; (ii) intermediate strain rates tests at 4.0 × 101 to 102 s−1 using an instrumented falling weight apparatus; and (iii) high strain rates at 0.5 × 103 to 1.5 × 103 s−1 using a tensile split Hopkinson bar. Furthermore, quasi-static and high strain rate tests were also performed for different temperatures, from room temperature up to 250 °C. Strain rate and temperature effects are also discussed for rolling and transverse direction, to identify the variation of sheet properties with loading direction. Finally, the constitutive fitting of the stress–strain curves to the widely employed Johnson–Cook material model equation is evaluated and also a new model is proposed based on a modified J–C model to account for the variation of strain hardening with strain rate.

Keywords: Hopkinson bar

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.

Keywords: Injury severity

The research on quasar {OJ} 287 has lasted over 100 years. {OJ} 287 exhibits the phenomenon of periodic two-peak outbursts with the eruptive period of 12 years. Observations are rather well interpreted with the black hole binary model. In this model, the secondary black hole moves around the primary black hole and crashes against the accretion disk of the primary black hole, causing outbursts. This model reasonably explains the light curves of {OJ} 287 and correctly predicts the time of future outbursts. These indirectly justify the precessional effect of general relativity and the existence of gravitational waves. The massive black hole in the center of galaxy is an important kind of gravitational wave source. However, the number of the galaxies with precisely determined kinematical equations of inner components is quite small. The precise kinematic orbits of black holes are provided by the black hole binary model, so the radiation of gravitational waves can be studied on the basis of these kinematic orbits. Based on the existing work, the evolutionary relations of the radiation power and waveform of gravitational waves with time are first derived by using the post-Newtonian approximation method. According to the current progress of the detection equipment of gravitational waves, i.e., {IPTA} (International Pulsar Timing Array), the direct detection of gravitational waves from {OJ} 287 may be possible within the future decade.

Keywords: quasars: individual: {OJ} 287

Introduction: This paper examines crash and safety statistics from the Emirate of Dubai in an attempt to identify factors responsible for making this population at greater risk of crashes compared to other countries. Problem: In developing countries such as the United Arab Emirates (U.A.E.), motor-vehicle-related mortalities frequently exceed those of the industrialized nations of North America and Europe. Method: Fatality and injury data used in the analysis mainly come from Dubai Emirate police reports and from other relevant international sources. Groups of the population are identified according to associated risk and exposure factors. Influence and strength of the most common risk factors are quantified using relative risk, the Lorenz curve, and the Gini index. Further analysis employed logit modeling, and possible predictors available in Dubai police reports, to estimate probability and odds ratios associated with drivers that are deemed responsible for causing traffic accidents. Results: Traffic fatality risk was found to be higher in Dubai, compared to some developed nations, and to vary considerably between different classes of road users and groups of the resident population. The likelihood of a driver causing an accident is considerably higher for those driving goods vehicles, but it is also associated with other factors. Impact: Results provide epidemiological inferences about traffic mortality and morbidity, and suggest priorities and appropriate measures for intervention, targeting resident population.

Keywords: Risk

The use of neural networks as global approximation tool in crashworthiness problems is here investigated. Neural networks are not only asked to return some meaningful indices of the structural behavior but also to reproduce load–time curves during crash phenomena. To contain the number of examples required for the training process, parallel subsystems of small neural networks are designed. Design points for the training process are obtained by explicit finite element analyses performed by PAMCRASH. The settlement of the points in the design domain is defined using a maximum distance concept. The procedure is applied to different typical absorption structures made of aluminum alloy: riveted tubes, honeycomb structures, longitudinal keel beam and intersection elements of helicopter subfloors.

Keywords: Crashworthiness

This paper analyses the base connection of partially encased composite columns while considering the solution of embedding the column in a concrete foundation block. The base connection is formed by a socket-type joint that is used for {RC} pre-cast columns, avoiding the brittle failure that usually occurs in traditional base joints made of plates and bolts due to crashing of the welds and degradation of the bonding. The experimental results from previous tests showed that the innovative joint is more ductile than the traditional joint, but the detailed analysis developed in this paper demonstrates that the fixed end rotation contributes to the global ductility of the joint. A non-linear 3D {FE} model is constructed and calibrated from the experimental results and is then used for parametric analyses. The influence of the embedded height is examined by determining its value that exploits the entire resistance of the column before the base concrete fails. Another parametric study using the 3D {FE} model is performed to define the elastic rigidity of the connection. Finally, a simple mono-dimensional model is assessed with a non-linear spring at the base that takes into account the elastic rigidity and the plastic behaviour of the base joint.

Keywords: Rotational capacity

The specific effects of vehicular type on the likelihood of an injury occurring are relatively unexplored. This study sought to assess the relative risk of injury to occupants of four-wheel drive vehicles and their counterparts in passenger cars. Data for 1143 occupants from all of the 454 crashes in Oklahoma, in 1995 that involved a four-wheel drive vehicle were used. Multiple logistic regression analysis determined the association between potential predictive factors and vehicular injury. Odds ratios revealed occupancy in a passenger car to be a major predictor of the likelihood of injury. Other factors include the driver being female, driving too fast, travel on curved or level roadways, and being hit laterally or from the rear.

Keywords: Four-wheel drive vehicles

In this work, boron steel sheet metal blanks were austenized and quenched at five different cooling rates ranging from 14 °C/s to 50 °C/s, which resulted in as-quenched microstructures that ranged from bainitic to martensitic respectively. Micro-hardness tests revealed a linear relationship between the Vickers hardness and percent area fraction of martensite and bainite present in the quenched specimens. Miniature tensile specimens were machined from the quenched blanks and tested in tension at four strain rates from 0.003 s−1 to 1075 s−1. For the 0.003 s−1 tests, the ultimate tensile strength (UTS) increased from 816 MPa to 1447 MPa for the 14 °C/s and 50 °C/s quench condition respectively. By elevating the strain rate from 0.003 s−1 to 1075 s−1, the {UTS} of the 14 °C/s specimens increased by 134 MPa, while the increase in {UTS} of the 50 °C/s specimens was measured to be 170 MPa for an equivalent change in loading rate. The percent area reduction of the fracture surface was 70% for the 14 °C/s specimens and decreased to 58% for the 50 °C/s specimens. The true stress versus effective plastic strain (flow stress) curves were used to develop the “Tailored Crash Model” (TCM) which is a constitutive model that is a function of strain, strain rate, and as-quenched Vickers hardness (or area fraction martensite/bainite). Scanning electron microscope and optical microscope images of the fracture surfaces revealed a transition from ductile to shear fracture behaviour as the quench condition increased from 14 °C/s to 50 °C/s.

Keywords: Hot stamping