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The National Academies

NCHRP 17-71 [Completed]

Proposed AASHTO Highway Safety Manual, Second Edition

  Project Data
Funds: $980,000
Research Agency: Kittelson & Associates, Inc.
Principal Investigator: Erin M. Ferguson
Effective Date: 10/12/2015
Completion Date: 3/20/2020

OBJECTIVE
 
The objective of this research was to develop and prepare a proposed Second Edition Highway Safety Manual (HSM) in a format suitable for adoption as an AASHTO publication. The proposed Second Edition will synthesize and incorporate relevant ongoing and completed research, related documents, and user feedback in order to expand the scope and quality of the HSM to increase application and improve its usability.

STATUS

The contract has been terminated by mutual agreement. Work products are being reviewed and development of the second edition of the HSM is tentatively expected to be completed in NCHRP Project 17-71A.

RESEARCH PLAN

The research was divided into four primary phases with two planned face-to-face interim meetings with the panel and research team. Each primary phase was contingent upon NCHRP approval of the previous phase results.
The research plan included the following components:
  • Review the existing HSM for errors, inconsistencies, and duplications in addition to the published errata.
  • Identify gaps, needed expansions and changes to current chapters, such as Chapter 2, “Human Factors in Road Safety,” Chapter 3, “Fundamentals,” Appendix A of Part C, Calibration Factor procedures, and others.
  • Develop a plan to obtain user feedback including but not limited to consulting with the AASHTO Standing Committee on Highway Traffic Safety (SCOHTS), Subcommittee on Safety Management (SCOHTS-SSM), specifically with its Task Group on Technical Safety Publication Oversight and Outreach, and the TRB Highway Safety Performance Committee (ANB25) to identify key issues to be considered in preparing the Second Edition of the HSM.
  • Identify and assemble the research results and related HSM materials that should be considered for inclusion to the Second Edition HSM.
  • Compile a list of broad-based issues, action plan, and proposed changes for review by the NCHRP Panel. These would include, as a minimum: (1) changes based on research and recently completed chapters, (2) identification of critical gaps in knowledge or gaps in the available HSM materials that have not been addressed, and (3) an action plan with recommendations to fill those gaps either with materials expected from ongoing research or with research to be conducted as part of this research effort.
  • Conduct the research needed to fill the gaps identified in the earlier task. Note: Research conducted by the research contractor is expected to fill small gaps and resolve inconsistencies in available materials, since large gaps are expected to be addressed in other ongoing identified funded research.
  • Develop a comprehensive initial first draft of the updated HSM incorporating the new results and new HSM materials and expansions to current chapters, and edit the draft to incorporate user feedback. Coordinate at a minimum with the AASHTO Safety Management Subcommittee (SCOHTS-SSM), and its Task Groupon Technical Safety Publication Oversight and Outreach, and the TRB Highway Safety Performance Committee (ANB25). The research contractor will gather feedback and consolidate comments from AASHTO and TRB and provide to NCHRP for panel review.
  • Obtain materials from all HSM-relevant related research that has been completed during the project period, and develop a second draft of the updated HSM incorporating those new materials, as well as revisions in response to comments on the initial first draft and the results of research completed.
  • As part of the development of the second draft, prepare and/or update computational examples that illustrate the intended application of HSM methodologies, and include the results of any needed small research efforts to close gaps or inconsistencies between the new material and existing material. Provide the second draft for NCHRP review to the AASHTO Safety Management Subcommittee Task Group, and the TRB Highway Safety Performance Committee. The contractor will receive feedback and consolidate comments from AASHTO and TRB and submit the results to the NCHRP. The NCHRP will vet the consolidated comments to the panel and provide feedback to the research team.
  • Develop a preliminary final draft of the updated HSM for review by NCHRP, AASHTO Safety Management Subcommittee Task Group, and the TRB Highway Safety Performance Committee. The contractor will receive feedback and consolidate comments from AASHTO and TRB and submit the results to NCHRP. The NCHRP will vet the consolidated comments to the panel and provide feedback to the research team.
  • Incorporate recommended changes and comments from the NCHRP panel into a final draft edition HSM report suitable for AASHTO publication. Develop a comprehensive list of items to be excluded from the HSM Second Edition and justifications. Document and log changes that also include the feedback received throughout the duration of this research between the existing HSM First Edition and the development of the new Second Edition HSM. Provide final version of the Second Edition HSM to AASHTO for balloting and eventual publication.
BACKGROUND
 
The AASHTO Highway Safety Manual (HSM) is rapidly becoming a key safety management and evaluation tool for state and local highway agencies; 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 high-priority research could not be completed without delaying publication. An example is the safety prediction models for freeways and interchanges developed under NCHRP Project 17-45--while this research is important, the decision was made to publish the First Edition without this material. Several other research efforts to develop models for additional facility types for inclusion in the HSM are underway and, like the freeways and interchanges chapters, each are considered critical to increasing safety knowledge and practice. The HSM has fostered significant advances in analytical methods in highway safety and this evolution continues; with increased knowledge, Safety Performance Functions (SPFs) and Crash Modification Factors (CMFs) being developed on an ongoing basis. Users and researchers now have gained experience with the HSM and have outlined priorities for enhancements to HSM chapters, procedures, and models. An example of current research that could be included in the next edition is an FHWA decision tree used to determine whether to develop a state-specific safety performance function or to calibrate the functions provided in the HSM. Beyond applying the HSM in specific situations such as network screening, crash diagnosis and design exceptions, state departments of transportation and other users are developing their own safety performance functions, policies, agency-wide training programs and pursuing other implementation activities that more completely integrate the information in the HSM. With the implementation of the existing HSM, errors and misunderstanding of appropriate applications have been noted. With increasing knowledge and the growing experience of the HSM user, additional needs are continuing to be identified. These needs have led to a significant amount of combined research through NCHRP, FHWA, and pooled fund initiatives. This research is further developing and promoting the quantitative, data-driven approach to safety. These research efforts are not specifically developing new chapters for the HSM or enhancing models already in the manual, but are expected to result in advances that are suitable for inclusion in the next edition HSM or other AASHTO documents such as the AASHTO “Green Book.” 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 HSM Second Edition will represent an important advance in safety management and support the expanding evaluation capabilities of highway agencies.

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