Proposed AASHTO Highway Safety Manual, Second Edition

The AASHTO Highway Safety Manual (HSM) ( has become a key safety management and evaluation resource for state and local roadway agencies; metropolitan planning organizations (MPOs); and the safety, design, and traffic engineering professional community. The HSM was developed largely through NCHRP research and the first edition was published in 2010. As the first edition was being developed, it was clear that some high-priority research could not be completed in time for inclusion in the HSM. One such example is the safety prediction models for freeways and interchanges developed under NCHRP Project 17-45, “Safety Prediction Methodology and Analysis Tool for Freeways and Interchanges” ( which was published as a Supplement to the first edition HSM by AASHTO. Several other research efforts to develop models for additional facility types for inclusion in the HSM are now complete or underway and are considered critical to increasing safety management and evaluation knowledge and practice. The HSM has fostered significant advances in analytical methods in roadway safety and this evolution continues; with increased knowledge, Safety Performance Functions (SPFs), Adjustment Factors (AFs), Crash Modification Factors (CMFs), and Calibration Factors (CFs) are being developed on an ongoing basis. Users and researchers have outlined priorities for enhancements to HSM chapters, procedures, and models. Beyond applying the HSM in specific situations such as network screening, crash diagnosis, and design exceptions, state departments of transportation and other road agencies are developing their own SPFs, policies, agency-wide training programs, and pursuing other implementation activities that more completely integrate the information in the HSM. With the implementation of the HSM, errors and misunderstanding of appropriate applications have been noted. With increasing knowledge and the growing experience of the HSM user, additional needs continue to be identified. These needs have led to a significant amount of combined research through NCHRP, FHWA, and pooled fund initiatives. This has included increased research and application related to pedestrian and bicyclist safety, systemic safety, human factors, and additional facility types. Incorporating this material throughout the HSM will take specialized knowledge and research skills in order to appropriately identify, evaluate, refine, and include this research in a manner suited to practitioners. The second edition of the HSM (HSM2) will represent an important advancement in safety management and support the expanding evaluation capabilities of transportation agencies. Work on the HSM2 began with NCHRP Project 17-71, “Proposed Highway Safety Manual, Second Edition.” That project began in October 2015 and made substantial progress. Additional effort is needed to complete the HSM2 in a timely manner so that practitioners can take advantage of the research that has been completed since the publication of the first edition HSM. The objective of this research is to complete the work begun in NCHRP Project 17-71 to develop and prepare a proposed HSM2 in a format suitable for adoption as an AASHTO publication. The proposed HSM2 will synthesize and incorporate relevant ongoing and completed research including finished NCHRP Project 17-71 deliverables, related documents, and user feedback in order to expand the scope and quality of HSM2 to increase application and improve its usability.


  • English


  • Status: Proposed
  • Funding: $480000
  • Contract Numbers:

    Project 17-71A

  • Sponsor Organizations:

    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

    American Association of State Highway and Transportation Officials (AASHTO)

    444 North Capitol Street, NW
    Washington, DC  United States  20001
  • Project Managers:

    Derr, B

  • Start Date: 20201215
  • Expected Completion Date: 0
  • Actual Completion Date: 0

Subject/Index Terms

Filing Info

  • Accession Number: 01751847
  • Record Type: Research project
  • Source Agency: Transportation Research Board
  • Contract Numbers: Project 17-71A
  • Files: TRB, RiP
  • Created Date: Sep 14 2020 3:04PM