Developing Safety Performance Functions for Rural Two-Lane Highways that Incorporate Speed Measures

The Highway Safety Manual (HSM) currently provides safety performance functions (SPFs) for several types of roadways and intersections. Highway agencies can calibrate the SPFs to local conditions for use in predicting expected safety outcomes for given roadway designs and safety features. These SPFs, and others developed in-house by highway agencies, are a function of annual average daily traffic (AADT), since the likelihood of crashes on a roadway is directly related to the number of vehicles using it. Speed, too, is generally understood to be an important factor in roadway safety performance. The severity of the crash is particularly sensitive to vehicle speeds, since the crash energy increases by the square of the vehicle velocity. Speed may also affect the probability of crash occurrence, although this relationship is less well-understood. Despite the importance of speed on safety, predictive models generally do not yet include speed measures. Research is needed to understand which speed measures (e.g., average speed, 85th percentile speed, speed variance, speed limit violation rate, etc.), in conjunction with geometrics, cross section, and context, are the best predictors of crash frequency and severity. The objective of this research is to develop a predictive methodology for rural two-lane, two-way highways, for consideration by the AASHTO HSM Steering Committee, that incorporates speed measures (or surrogates for speed measures) to estimate crash frequency and severity. The methodology shall be data-driven and suitable for inclusion in the predictive methods of the HSM and include SPFs and crash modification factors (CMFs) or alternative models with the intent to advance the science of safety prediction. The methodology shall be sensitive to operational, geometric, contextual, and mobility factors across modes. The research shall coordinate with the activities of AASHTO, TRB, and FHWA on the development of the HSM.

• Record URL:
  http://apps.trb.org/cmsfeed/TRBNetProjectDisplay.asp?ProjectID=4574
• Supplemental Notes:
  • Contract to a Performing Organization has not yet been awarded.

Language

• English

Project

• Status: Proposed
• Funding: $500000
• Contract Numbers:

  Project 17-92

• Sponsor Organizations:

  American Association of State Highway and Transportation Officials (AASHTO)

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

  National Cooperative Highway Research Program

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

  Federal Highway Administration

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

  Harrigan, Edward

• Start Date: 20190319
• Expected Completion Date: 0
• Actual Completion Date: 0

Subject/Index Terms

• TRT Terms: Crash rates; Crash severity; Highway safety; Mathematical prediction; Performance measurement; Rural highways; Speed control; Speed measurement; Two lane highways
• Identifier Terms: Highway Safety Manual; Safety Performance Functions
• Subject Areas: Highways; Operations and Traffic Management; Safety and Human Factors;

Filing Info

• Accession Number: 01672553
• Record Type: Research project
• Source Agency: Transportation Research Board
• Contract Numbers: Project 17-92
• Files: TRB, RiP
• Created Date: Jun 18 2018 3:03PM