Updated and Regional Calibration Factors for Highway Safety Manual Crash Prediction Models

There is no doubt that there is a significant need for improving the explicit role of safety in making decisions on roadway planning, design, maintenance, construction, and operations. In order to achieve the greatest return on the investment of limited budgets, it is imperative that decisions are made based on the best information regarding the safety implications various design alternatives and engineering treatments. The 1st edition of the Highway Safety Manual (HSM) that has been developed through funding from the American Association of State and Highway Transportation Officials (AASHTO) and Federal Highway Administration (FHWA) provides the latest analytical tools and techniques for quantifying the safety effects of decisions made in planning, design, operations, and maintenance. Part C of the HSM provides prediction models that can be used by states for predicting the safety impact of design alternatives. In order to use these prediction models, they need to be calibrated using data from the jurisdiction. The North Carolina Department of Transportation (NCDOT) Project 2009-07 (Procedure for Curve Warning Signing, Delineation, and Advisory Speeds for Horizontal Curves) conducted by North Carolina State University and University of North Carolina (UNC's) Highway Safety Research Center (HSRC) estimated calibration factors for roadway segments on rural two lane roads. NCDOT Project 2010-09 (Development of Safety Performance Functions for North Carolina) conducted by UNC's HSRC estimated calibration factors for the other prediction models in Part C of the HSM. These calibration factors have been extensively used by the NCDOT Traffic Safety Unit as part of their decision making process. HSM recommends that these calibration factors be updated every three years. In addition, the Traffic Safety Unit desires to have separate calibration factors for the three different regions in North Carolina (Western, Piedmont, and Coastal) to properly account for differences in terrain, climate, and driver population. The overall objective is to estimate the calibration factors for all the prediction models in Part C of the HSM (that are of interest to NCDOT) as well as calibration factors for freeway models that are slated to be part of the next HSM based on the latest five years of roadway, traffic, and crash data from North Carolina. Separate calibration factors for the three different regions in North Carolina (Western, Piedmont, and Coastal) will be estimated as well. This research should also give some guidance regarding how often calibration factors should be updated based on how much the calibration factors change from year to year. If there is little change in the calibration factors from year to year, it may not be critical to update them very often.

  • Supplemental Notes:
    • Contract to a Performing Organization has not yet been awarded.


  • English


  • Status: Active
  • Sponsor Organizations:

    North Carolina Department of Transportation

    Research and Development
    1549 Mail Service Center
    Raleigh, NC  United States  27699-1549
  • Project Managers:

    Morrison, Ernest

  • Start Date: 20150801
  • Expected Completion Date: 0
  • Actual Completion Date: 0

Subject/Index Terms

Filing Info

  • Accession Number: 01582847
  • Record Type: Research project
  • Source Agency: North Carolina Department of Transportation
  • Files: RiP, STATEDOT
  • Created Date: Dec 8 2015 4:19PM