Calibration and Development of Safety Performance Functions for Rural Highway Facilities in Idaho

In 2010, the American Association of State Highway and Transportation Officials (AASHTO) released the Highway Safety Manual (HSM) as a resource to include safety in the decision-making process for transportation professionals. HSM provided analytical tools and techniques for quantifying the potential effects on crashes as a result of decisions made in planning, design, operations, and maintenance. The implementation of HSM methodologies provides a cost-effective approach that contributes to a reduction in traffic crashes and ensures well-planned engineering, education, and enforcement countermeasures. In this project, HSM calibration factors and state-specific Safety Performance Functions (SPFs) were developed based on Idaho crash history. The analysis focused on three rural facility types: two-lane two way highways, 3-leg stop controlled intersections, and 4-leg stop controlled intersections. The results of the analysis showed that the observed number of crashes for Idaho sites were consistently lower than those estimated using the HSM crash prediction models. The HSM calibration factors developed for three facility types considered in the analysis are 0.87, 0.56, and 0.62, respectively. The results also showed that Idaho-specific SPFs provided better crash predictions for the two-lane two-way highways roadway segments and the 3-leg stop controlled intersections. For the 4-leg controlled intersections, the Idaho-specific SPF did not provide significant crash prediction improvement over the HSM SPF.


  • English


  • Status: Completed
  • Funding: $65200.00
  • Contract Numbers:

    RP 225

  • Sponsor Organizations:

    Idaho Transportation Department

    P.O. Box 7129, 3311 West State Street
    Boise, ID  United States  83707-1129
  • Project Managers:

    Jennings, Brent

    Tomlinson, John

  • Performing Organizations:

    University of Idaho, Moscow

    Office of Sponsored ProgramsNational Institute for Advanced Transportation Technology
    P.O. Box 443020
    Moscow, ID  United States  83844-3020
  • Principal Investigators:

    Abdel-Rahim, Ahmed

  • Start Date: 20130107
  • Expected Completion Date: 0
  • Actual Completion Date: 20160401
  • Source Data: RiP Project 33238

Subject/Index Terms

Filing Info

  • Accession Number: 01560831
  • Record Type: Research project
  • Source Agency: Idaho Transportation Department
  • Contract Numbers: RP 225
  • Files: RIP, STATEDOT
  • Created Date: Apr 23 2015 1:00AM