Update of Crash Modification Factors for the Highway Safety Manual

Highway safety practitioners were given a significant new tool in 2010 with the publication of the first edition of the AASHTO Highway Safety Manual (HSM). In Part D of the HSM, crash modification factors (CMFs) are provided for a variety of treatments. These CMFs provide practitioners with the means to estimate the safety effects of countermeasures. By the time the second edition HSM is published, many more important CMFs will have been developed. It is critical that the next edition of the HSM incorporate these CMFs in order to continue to push forward this significant tool. In the first edition HSM, only the best available CMFs for individual treatments are provided. Questions that have arisen since the first edition of the HSM include: (a) Do the inclusion criteria need to be revised? (b) Should more than one CMF be presented for a particular countermeasure? (c) Is uncertainty of the CMFs adequately represented? (d) Should CMFs from multiple studies for the same treatment be combined and if so, how? There is a need to establish inclusion criteria for CMFs and guidelines on how CMFs should be incorporated in the next edition of the HSM. Also, CMFs for use in the second edition of the HSM need to identified, assembled, and documented. The objectives of this research are to: (a) Assess the current criteria and existing process for evaluating and identifying the quality of CMFs for appropriate use with the HSM. (b) Develop proposed revisions to the criteria and process, including how existing and new CMFs may be incorporated in the HSM. Provide guidance for practitioner application of the revised process. (c) Apply the evaluation criteria to identify and assess CMFs and develop a list of appropriate CMFs for the HSM. CMFs to be studied are those listed in the FHWA CMF Clearinghouse. The research results are intended for possible inclusion in a future second edition of the HSM.

  • Record URL:
  • Supplemental Notes:
    • The revised final report has been published as NCHRP Research Report 1029: Crash Modification Factors in the Highway Safety Manual: A Review and an associated publication NCHRP Web-Only Document 352: Crash Modification Factors in the Highway Safety Manual: Resources for Evaluation


  • English


  • Status: Completed
  • Funding: $845000
  • Contract Numbers:

    Project 17-72

  • Sponsor Organizations:

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590

    American Association of State Highway & Transportation Officials (AASHTO)

    444 North Capitol Street, NW, Suite 225
    Washington, DC  United States  20001

    National Cooperative Highway Research Program

    Transportation Research Board
    500 Fifth Street, NW
    Washington, DC  United States  20001
  • Project Managers:

    Deng, Zuxuan

  • Performing Organizations:

    University of North Carolina, Chapel Hill

    Chapel Hill, NC  United States  27514
  • Principal Investigators:

    Srinivasan, Raghavan

  • Start Date: 20150831
  • Expected Completion Date: 20220704
  • Actual Completion Date: 0
  • Source Data: RiP Project 37544

Subject/Index Terms

Filing Info

  • Accession Number: 01543358
  • Record Type: Research project
  • Source Agency: Transportation Research Board
  • Contract Numbers: Project 17-72
  • Files: TRB, RIP
  • Created Date: Nov 13 2014 1:01AM