Rural Speed Safety Project for USDOT SDI






Subasish Das, Ph.D.

December 7, 2018


Defining the Research Space


Research questions:
  • How do human factors become dominant in crash severities?
  • How does a pedestrian’s body dynamics effect the driver?
  • Do the association rules identify any domain specific relationship?

Challenges

  • Speed data- quantity, usability
  • Two linear systems- crash/roadway geometry/traffic volume data and speed data
  • Data structure for the evaluation
  • Excess number of rural sites with zero crashes

Challenge= Speed data- quantity, usability

  • Solution= NPMRDS data are available to DOTs / able to explore greater number of speed measures

Challenge= Two linear systems- crash/roadway geometry/traffic volume data and speed data

  • Conflation of two linear systems

Challenge= Data structure for the evaluation

  • Create 3 data structures where Data Structure 1 and 2 will address Q1 and Data Structure 3 will addrsess Q2

Challenge= Excess number of rural sites with zero crashes

  • Develop best-fit statistical models to address zero crashes
  • Currently used models are : negative binomial (NB), NB Lindley (NBL), and random parameter NBL

Evaluation

  • Exploratory data analysis
  • Deveoping models by facility type
    • Predicted crashes= function (segment length, traffic volume, other imporatant geometry, and speed measures)
    • This project can inform Highway Safety Manual (HSM) models by incorporating speed measures
  • Develop expected crashes
    • Expected crashes= Incorporate weighting factor as described in the HSM

Statistical Analysis Findings

  • Q1: Do different speed measures contribute to crash outcomes?
    • Yes!
    • Developed decision support tool to illustrate number of expected crashes on segments
  • Q2: Is there more variability in speeds just prior to a crash?
    • Yes!
    • Developed models that use travel speed to classify crash and non-crash event

Prototype of Decision Support Tool

Live app link: https://ldwhite.shinyapps.io/RuralSpdSafety_Demo/

Next Steps by Questions

  • Q1: Do different speed measures contribute to crash outcomes?
    • Refine SPFs
  • Q2: Is there more variability in speeds just prior to a crash?
    • Refine model fitness

Additional Slides

Data Preparation

  • Three States: North Carolina, Washington, and Ohio
  • Three Databases
    • Highway Safety Information System (HSIS)
    • Highway Performance Monitoring System (HPMS)
    • National Performance Management Research Data Set (NPMRDS)
  • Year: 2015
  • Task
    • Conflate 3 databases for 3 states

SPFs at Segment level (Washington)

SPFs at Segment-temporal level (Washington)

Proximity of Crashes at Segment-temporal Level

Questions?