Quantitative Safety Analyses for Highway Applications (2025)
Chapter: 3 Assessment of Research for Potential Incorporation into HSM2
CHAPTER 3
Assessment of Research for Potential Incorporation into HSM2
The NCHRP Project 17-71A research team assessed completed and ongoing research for potential incorporation into HSM2 by considering factors such as:
- Likelihood of the research being completed by a suitable date,
- Quality of the research,
- Compatibility with material in the first edition of the HSM that will remain in HSM2,
- Compatibility with other new research considered for incorporation in HSM2,
- Value to HSM2 users, and
- Impacts of incorporating the research on the overall NCHRP Project 17-71A budget and schedule.
The research team reviewed and assessed research specifically conducted for HSM application, including projects charged with developing draft material for HSM2 aimed at filling gaps or correcting inconsistencies. The research team also reviewed other recently initiated or published safety-related research.
Before conducting this review, the research team reviewed the list of reference materials and completed/ongoing projects in the Phase I Interim Report from NCHRP Project 17-71 that the 17-71 team identified as potential sources of information to incorporate into HSM2. The NCHRP Project 17-71A team found that, with the development of draft HSM2 Parts A, B, and D being further along than HSM2 Part C, most of the reference materials identified by the NCHRP Project 17-71 team for potential incorporation into HSM2 Parts A, B, and D had already been incorporated into the draft HSM2 chapters. However, with HSM2 Part C chapters, only a few references had been incorporated into the draft freeway and ramp chapters. Therefore, for Task 3, the focus was on identifying more recent references and ongoing or completed research beyond what the 17-71 team had previously identified for potential incorporation into HSM2 Parts A, B, and D. For HSM2 Part C, where possible, the NCHRP Project 17-71A team conducted a more thorough review of completed and ongoing research and available materials to assess the likelihood of incorporating the materials into the draft HSM2 chapters. This task also involved contacting project leaders and sponsors of ongoing research projects to learn more about the status of a project and to request interim deliverables or final deliverables/reports that may not yet be available to the general public.
The results of this assessment were presented in a white paper and submitted to NCHRP at the conclusion of Task 3 for review by the project panel. This chapter of the final report summarizes the results of that assessment.
Review of Potential Materials for HSM2 Part A
For HSM2 Part A, no additional resources were identified for Chapter 1: Introduction and Overview. About 10 sources were identified that could be used to augment or update information in the draft chapter on human factors. In addition, NCHRP Project 22-45, “Informing
the Selection of Countermeasures by Evaluating, Analyzing, and Diagnosing Contributing Factors That Lead to Crashes” (in progress at the time of this writing), and NCHRP Project 17-80, “Expansion of Human Factors Guidelines for Road Systems, Second Edition” (recently completed), were identified as two projects from which potential material/information could be obtained for incorporation into the human-factors chapter. NCHRP Project 22-46, “Human Factors Guidelines for Road Systems, Proposed 4th Edition,” was set to begin during the writing of this report, but given the schedules of both NCHRP Projects 17-71A and 22-46, information from NCHRP Project 22-46 was not incorporated into this report. However, the research team will continue to monitor the status of this research. The research team believes most of the foundational sources have already been incorporated into the draft fundamentals chapter, with the exception of potential resources related to the safe-system approach. Three reports and a PowerPoint presentation, flyer, and website were identified as potential sources to obtain information on the safe-system approach for this chapter. The research team also believes most of the foundational sources have already been incorporated into the draft HSM2 chapter on pedestrians and bicyclists, with the exception of potential information and findings from NCHRP Project 17-80, “Expansion of Human Factors Guidelines for Road Systems, Second Edition,” and NCHRP Project 17-84, “Pedestrian and Bicycle Safety Performance Functions for the Highway Safety Manual,” which were not yet completed at the time of this writing.
Review of Potential Materials for HSM2 Part B
The relevant foundational sources had already been incorporated into the draft HSM2 Part B chapter on network screening, with the exception of potential SPFs from NCHRP Project 17-62, “Improved Prediction Models for Crash Types and Crash Severities.” There was interest from reviewers of the draft diagnosis chapter to include greater consideration of human-factors issues. In collaboration with the work being done for the human-factors chapter (Chapter 3 in HSM2 Part A), the research team anticipated referencing the Primer on the Joint Use of the Highway Safety Manual (HSM) and the Human Factors Guidelines (HFG) for Road Systems (Campbell et al., 2018) and findings from NCHRP Project 22-45 (Campbell et al., 2024) and NCHRP Project 17-80 (Brown et al., 2022). These same three references/projects were identified as also containing material suitable for inclusion in the countermeasure selection chapter. The NCHRP Project 17-71A research team identified three sources that could potentially be used to augment or update information in the draft chapter on economic appraisal (two of which address economic analysis related to systemic safety). Three sources were identified that could potentially be used to include a discussion of systemic safety projects in the chapter on project prioritization. Reports from NCHRP Project 17-78, “Understanding and Communicating Reliability of Crash Prediction Models” (Srinivasan et al., 2021a; 2021b), which focus on the mismatch of CMF and SPF base conditions, were identified as potential sources of information for the draft chapter on safety effectiveness evaluation. It was also anticipated that a new chapter on macro-level safety planning from NCHRP Project 17-81, “Proposed Macro-Level Safety Planning Analysis Chapter for the Highway Safety Manual,” would be available for potential incorporation into HSM2 Part B.
Review of Potential Materials for HSM2 Part C
For the new HSM Part C chapter on developing, calibrating, and using safety performance functions and crash prediction models, which had not yet been written at the conclusion of NCHRP Project 17-71, the NCHRP Project 17-71A research team identified one new source not included in the outline of this chapter that could be referenced within this introductory chapter to Part C. For the predictive chapters on rural two-lane roads, rural multilane highways,
urban/suburban arterials, freeways, and ramps, the research team reviewed available information from the following NCHRP projects:
- NCHRP Project 17-54, “Consideration of Roadside Features in the Highway Safety Manual”
- NCHRP Project 17-58, “Safety Prediction Models for Six-Lane and One-Way Urban and Suburban Arterials”
- NCHRP Project 17-62, “Improved Prediction Models for Crash Types and Crash Severities”
- NCHRP Project 17-68, “Intersection Crash Prediction Methods for the Highway Safety Manual”
- NCHRP Project 17-70, “Development of Roundabout Crash Prediction Models and Methods”
- NCHRP Project 17-72, “Update of Crash Modification Factors for the Highway Safety Manual”
- NCHRP Project 17-81, “Proposed Macro-Level Safety Planning Analysis Chapter for the Highway Safety Manual”
- NCHRP Project 17-84, “Pedestrian and Bicycle Safety Performance Functions for the Highway Safety Manual”
- NCHRP Project 17-85, “Development and Application of Crash Severity Models for the Highway Safety Manual”
- NCHRP Project 17-89, “Safety Performance of Part-Time Shoulder Use on Freeways”
- NCHRP Project 17-89A, “HOT/HOV Freeway Crash Prediction Method for the Highway Safety Manual”
- NCHRP Project 17-92, “Developing Safety Performance Functions for Rural Two-Lane Highways That Incorporate Speed Measures”
Based on this review, the research team believes models from NCHRP Projects 17-62, 17-68, 17-70, and 17-84 could potentially be incorporated into the rural two-lane chapter. Models from NCHRP Projects 17-62, 17-68, 17-70, and 17-84 could be incorporated into the rural multilane chapter. Models from NCHRP Projects 17-58, 17-68, 17-70, and 17-84 could be incorporated into the urban/suburban arterial chapter. Models from NCHRP Projects 17-89 and 17-89A could be incorporated into the freeway chapter (or potentially become their own chapters), and models from NCHRP Project 17-68 could be incorporated into the ramp chapter.
Review of Potential Materials for HSM2 Part D
The foundational sources have already been incorporated into the draft HSM2 Part D chapters, either in NCHRP Project 17-71 or in subsequent work in NCHRP Project 17-71A.
