Methodology to Predict the Safety Performance of Urban and Suburban Arterials

Abstract

The Transportation Research Board (TRB) and the American Association of State Highway and Transportation Officials (AASHTO) have begun a major initiative to develop a Highway Safety Manual (HSM). The HSM began from recognition of the fact that, for safety to receive proper consideration in the highway project development process, analysts need tools to make quantitative statements about the safety effects of proposed projects or design alternatives. The key components of the HSM will be: Part I—Introduction and Fundamentals; Part II—Knowledge; Part III—Predictive Methods; Part IV—Safety Management of a Roadway System; and Part V—Safety Evaluation. HSM Part III will consist of chapters that provide safety prediction methodologies for specific types of highway facilities. The TRB Task Force plans that the first edition of the HSM should include safety prediction methodologies for rural two-lane highways, rural multilane highways, and urban and suburban arterials. These methodologies would address the safety performance of both roadway segments and at-grade intersections on these facility types. A prototype chapter on rural two-lane highways for use in HSM Part III has already been developed to illustrate the potential format and scope for such chapters. This report presents research results which document the development of a draft HSM chapter presenting a safety prediction methodology for urban and suburban arterials. This is the first safety prediction methodology developed specifically for the HSM. This report presents the results of the literature review, the survey of potential HSM users, the recommended structure of the safety prediction methodology, and the recommended work plan for the methodology development. Chapter 1 of this report provides an introduction to the report. Chapter 2 presents information related to the safety performance of urban and suburban arterials, including the results of the literature review and an HSM user survey. Chapter 3 summarizes the recommended structure for the safety prediction methodology. Chapter 4 presents the development of the project database. Chapter 5 documents the development of the base models and adjustment factors used in the HSM methodology, while Chapter 6 documents the accident modification factors (AMFs) used in the methodology. The HSM methodology is summarized in Chapter 7. Chapter 8 presents the results of a validation study in which the safety prediction methodology was applied to sites in jurisdictions other than those used in its development. Chapter 9 presents the conclusions and recommendations of the research. Appendix A presents the results of the survey of state and local highway agencies, MPOs, and TRB Task Force members. Appendix B presents a draft of HSM Chapter 10 which incorporates the safety prediction methodology.