Traffic Speed Effects on Highway Safety Manual Crash Prediction Models

Speed management and data-driven safety analysis are priority topics for the highway safety community. A key gap in the body of knowledge is limited understanding of traffic speed effects in the crash frequency and severity prediction models for most facility types. It is known that the severity of motor vehicle crashes increases with increasing traffic speed, and speed may influence crash frequency. However, speed is correlated with nearly every other factor in the American Association of State Highway and Transportation Officials (AASHTO) Highway Safety Manual (HSM) crash frequency and severity prediction methods. As a result, current prediction approaches do not seem to incorporate traffic speed effects well and may even show counterintuitive results. Improving the consideration of traffic speed effects in the models may result in more realistic and insightful results. Given the correlation of traffic speed with other roadway and intersection features, innovative methods of quantifying speed effects in crash prediction methods in addition to regression modeling should be considered. Research is needed to find ways to incorporate traffic speed effects into HSM crash prediction models to make them more accurate and better suited toward developing designs based on the Safe System Approach. The objective of the research is to develop implementable methods to incorporate the effects of traffic speeds on the prediction of crash frequency and severity. The proposed methods should be applicable to different roadway facility types, in a format compatible with HSM methods to support the work of state departments of transportation (DOTs) and other users of the manual.

• Record URL:
  • http://apps.trb.org/cmsfeed/TRBNetProjectDisplay.asp?ProjectID=5872
• Supplemental Notes:
  • Contract to a Performing Organization has not yet been awarded.

Language

• English

Project

• Status: Proposed
• Funding: $750,000.00
• Contract Numbers:

  Project 17-139

• Sponsor Organizations:

  National Cooperative Highway Research Program

  Transportation Research Board
  500 Fifth Street, NW
  Washington, DC  United States  20001

  American Association of State Highway and Transportation Officials (AASHTO)

  444 North Capitol Street, NW
  Washington, DC  United States  20001

  Federal Highway Administration

  1200 New Jersey Avenue, SE
  Washington, DC  United States  20590
• Project Managers:

  Deng, Zuxuan

• Start Date: 20260801
• Expected Completion Date: 0
• Actual Completion Date: 0

Subject/Index Terms

• TRT Terms: Crash rates; Crash severity; Predictive models; Traffic speed
• Identifier Terms: Highway Safety Manual
• Subject Areas: Highways; Planning and Forecasting; Safety and Human Factors;

Filing Info

• Accession Number: 01956569
• Record Type: Research project
• Source Agency: Transportation Research Board
• Contract Numbers: Project 17-139
• Files: TRB, RIP
• Created Date: May 28 2025 10:16AM