CHAPTER 2

Review of Materials from NCHRP Project 17-71

In the early stages of the research, the NCHRP Project 17-71A team conducted a review of materials from NCHRP Project 17-71 to assess the status of work begun under that project toward the production of HSM2. The materials available from NCHRP Project 17-71 included selected HSM2 draft chapters, review comments on those chapters, responses to those comments, plans for incorporating new material into chapters, and a review of the preceding material by the NCHRP Project 17-71A panel and the AASHTO Steering Committee on the HSM. This chapter of the final report summarizes the NCHRP Project 17-71A research team’s primary findings from the review of materials from NCHRP Project 17-71.

General Status of HSM2 Parts A, B, C, and D at the Conclusion of Project 17-71

This section presents the general status of HSM2 Parts A, B, C, and D as available at the conclusion of NCHRP Project 17-71, based on the Project 17-71A research team’s review of the available materials. Table 1 shows the outline for the HSM2, as recommended by the NCHRP Project 17-71 team. The summaries of HSM2 Parts A, B, C, and D presented in the remainder of this chapter are based on this outline.

The following discussion summarizes the objectives of each HSM part and its status at the conclusion of NCHRP Project 17-71. Chapter 5 of this report describes changes to the NCHRP Project 17-71 outline and materials made during NCHRP Project 17-71A. Note that many of the HSM2 chapter numbers proposed in NCHRP Project 17-71 (and used in the following discussion in this chapter) were subsequently changed as documented in Chapter 5 of this report.

Draft Part A—Introduction, Human Factors, and Fundamentals

The HSM2 Part A content is intended to set the stage for HSM use. To address this, the individual chapters are preceded with a preface that introduces the document’s intended use and format. Following this brief section, Part A includes three chapters (Introduction and Overview, Human Factors, and Fundamentals). All three chapters were reviewed at least once by the NCHRP Project 17-71 panel and external stakeholders. Primary issues identified in this review were a need to update the HSM2 organization and enhance linkage to other sections of HSM2. For Chapter 2, the reviewers suggested that concrete “actionable” human-factors content would greatly enhance the current information. The reviewers also suggested that the distinction in terminology between “human factors” and “driver behaviors” be clarified. There was also found to be a need to better integrate the components of Chapter 2 with content in the rest of the HSM2

Table 1. Outline of HSM2 recommended by NCHRP Project 17-71 team.

(particularly Part B—Roadway Safety Management Process) and sample problems. The majority of comments resulting from the review of Chapter 3: Fundamentals still needed to be addressed. One outstanding issue was the recommendation by one reviewer that the Fundamentals chapter be reorganized to enhance the flow of the chapter.

Draft Part B—Roadway Safety Management Process

For HSM2 Part B, outstanding issues identified in the review of the NCHRP Project 17-71 materials related to bringing new chapters up to the appropriate quality, integrating content across chapters, and adding or reconciling methods within chapters. For example, the current HSM2 Chapter 4: Pedestrian and Bicycle Considerations was found to need substantial editing to separate the presentation of pedestrian and bicycle modes. The NCHRP Project 17-71 materials for HSM2 Chapter 4 were found to present the pedestrian and bicycle modes as if the issues were the same in all cases. Similarly, panel comments indicated that HSM2 Chapter 5: Systemic Safety Management Process needed additional work to remove contradictions about data usage and to develop continuity between the systemic, proactive approach and traditional crash concentration approaches, and to provide better coordination between the pedestrian and bicycle chapter and the systemic process chapter.

Review comments that addressed integration of content across chapters indicated that there is an interest in potentially integrating material from the pedestrian and bicycle chapter into the systemic process chapter and integrating systemic safety analysis content into other HSM2 Part B chapters (e.g., Chapter 8: Select Countermeasures, Chapter 9: Economic Appraisal, and

Several issues identified for Chapter 18 pertain to the consistency or coordination of Chapter 18 with other chapters or parts of HSM2. One issue that was raised by reviewers is that Part D is the only HSM2 part that has its introduction presented as a separate chapter; Parts A, B, and C are not structured this way. Another issue raised by a reviewer is whether there may be some redundancy between the content of Chapter 18 and Chapter 3. Finally, one reviewer asked whether Chapter 18 should include a discussion of the difference in the application of the Part B predictive method and the Part C predictive method.

In the discussion of the safety management and project development processes, Chapter 18 states that project prioritization “feeds into the project development process, enabling decision-makers to consider safety-motivated projects in conjunction with resurfacing, rehabilitation, reconstruction, and new construction projects” (AASHTO, 2010). One reviewer recommended expanding this discussion to address the fact that the project prioritization process feeds into more than just resurfacing, restoration, or rehabilitation (3R) and resurfacing, restoration, rehabilitation, and reconstruction (4R) projects [e.g., operations projects, intelligent transportation system (ITS) projects, maintenance activities, stand-alone safety projects, paving projects].

Some issues raised in the review comments pertain to terminology used in Chapter 18. Safety effectiveness–related terms such as “safety effects” and “safety impacts” are used throughout the chapter, and several reviewers recommended that this terminology be replaced with terms such as “potential crash reduction” or “crash potential.” There was also an issue expressed by reviewers that the terminology in Chapter 18 is inconsistent with terminology used in HSM1 (i.e., definitions for new terms as well as existing terms do not match exactly the definition used in HSM1). The definitions for the common terms should be reviewed for consistency in NCHRP Project 17-71A to determine if any changes are appropriate. A style and usage guide with key phrases to use and avoid in the HSM2 may help address this issue (see Chapter 4 and Appendix A in this report).

A key issue in draft HSM2 Part D reviews was whether information should be presented in Appendices D1, D2, and D3, as was done in HSM1, or whether that information should be integrated into the Part D chapters in a similar manner to the handling of analogous material in Parts A, B, and C.

Status of Reviews and Outstanding Comments for Draft HSM2 Chapters

For HSM2 chapters that had been written/edited and reviewed but had not been updated to address outstanding comments, the research team reviewed the outstanding comments and broadly grouped them into three categories to get a general sense of the level of effort likely needed to develop the draft chapters in final form suitable for balloting by AASHTO:

1. Editorial, style guide, language review, text consistency across chapters comments
2. Simple technical comments
3. Substantive technical or reorganization of chapter comments

For the first two categories (editorial, style guide, language review, text consistency across chapters comments; and simple technical comments), the NCHRP Project 17-71A research team planned to address these comments as appropriate with available resources. For the last category (i.e., substantive technical or chapter reorganization comments), the NCHRP Project 17-71A research team planned to address as many of these comments as practical with the available resources, but some would require additional funds and time to address.

Table 2 summarizes the status of each draft HSM2 chapter at the conclusion of NCHRP Project 17-71, indicating whether the draft chapter had been written/edited, the number of times it was reviewed by the NCHRP Project 17-71 panel or external stakeholders, the number of outstanding comments still to be addressed at the conclusion of NCHRP Project 17-71A, and

Table 2. Status of reviews of draft HSM2 materials by the NCHRP Project 17-71 panel and external stakeholders at the conclusion of NCHRP Project 17-71.

whether available comments have been vetted as well as suggested responses to the individual comments provided.

Summary of Status of Materials from NCHRP Project 17-71

The status of materials from NCHRP Project 17-71 can be summarized as follows. The development of draft chapters for HSM2 Parts A, B, and D was further along in NCHRP Project 17-71 than the development of draft chapters for HSM2 Part C. The overall outline/structure for the HSM2 as proposed during NCHRP Project 17-71 has been reevaluated in NCHRP Project 17-71A, as appropriate, to create new chapters, combine existing materials or chapters, change the order of chapters, and incorporate recently completed research. Work on revising existing text or writing new text for the HSM2 to fit within the revised outline has been completed in NCHRP Project 17-71A. The completed HSM2 text will be provided to AASHTO by NCHRP at the conclusion of NCHRP Project 17-71A for review and balloting by appropriate AASHTO committees.