The National Academies

NCHRP 17-71A [Pending]

Proposed AASHTO Highway Safety Manual, Second Edition

  Project Data
Funds: $480,000
Contract Time: 24 months
Staff Responsibility: B. Ray Derr

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.


Proposals have been received and are being evaluated by the project oversight panel.

The AASHTO Highway Safety Manual (HSM) (http://www.highwaysafetymanual.org/Pages/default.aspx) 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” (https://apps.trb.org/cmsfeed/TRBNetProjectDisplay.asp?ProjectID=2512) 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 research plan should include, at a minimum, the following components:
  •  A thorough review of the material from NCHRP Project 17-71.
  •  An assessment of research that could be successfully incorporated into the HSM2 (considering factors such as likelihood of the research being completed by an suitable date, compatibility with other parts of the HSM2, value to HSM2 users, and impacts of incorporating the research to the project’s budget and schedule).
  • Glossary of terms and phrases to be used and avoided in the HSM2. NCHRP LRD 83: Guidelines for Drafting Liability Neutral Transportation Engineering Documents and Communication Strategies (http://www.trb.org/Main/Blurbs/181064.aspx)should be a useful resource in this effort.
  •  An interim report that provides an updated work plan and schedule for chapter development, review, and revision.
    •  For each chapter, describe the approach and level of effort (including budget) needed to produce a viable HSM2 (including development of sample problems). Options to add value to the chapter (for example, by incorporating additional research into the material) should also be described along with their impacts to the project’s budget and schedule. Incorporation of the single state calibration factors being developed in NCHRP Project 17-72, “Update of Crash Modification Factors for the Highway Safety Manual,” should be included in the baseline plan (see Special Note B). 
    •  Widespread external chapter reviews are not expected though targeted external reviews may be desirable for new chapters and those that have had extensive revision. Proposals should thoroughly describe the intended review process and tools.
  •  A schedule for panel oversight that includes web conferences every calendar quarter and in-person meetings in June 2021 and June 2022 (tentatively). Costs associated with these interactions should be explicit in the proposal budget; the cost of travel for panel members will be the responsibility of NCHRP.
The final deliverables shall include: (1) the proposed HSM2, delivered in an electronic format suitable for transmittal to AASHTO for balloting and eventual publication; (2) a brief report documenting the entire research effort; and (3) a Microsoft® PowerPoint presentation detailing the revised chapter outline and significant differences between the first and second editions (with the rationale for those differences explained in the speaker notes).
A. The project currently has $480,000 in funds available but it is not clear this will be sufficient to produce a viable HSM2 suitable for publication by AASHTO. The contractor, project oversight panel, and NCHRP will (1) describe and prioritize the work towards the completion of the HSM2 that can be accomplished given the funds available and (2) estimate and justify the additional funds needed to produce a comprehensive HSM2. The estimate will be refined during the course of this project and will be considered for NCHRP funding.
B. NCHRP Project 17-83, “Briefings and Training Materials for Implementation of the Highway Safety Manual, Second Edition,” will develop spreadsheets implementing the HSM2 methodologies so NCHRP Project 17-71A does not include any spreadsheets or other analytical tools as deliverables. The selected contractor will be expected to coordinate with the NCHRP Project 17-83 contractor.
C. The contractor will participate in discussions on the efficacy of AASHTO publishing some portions of the HSM2 prior to the completion of the full HSM2 with NCHRP and AASHTO early in the project.

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