National Academies Press: OpenBook

Guide for Quantitative Approaches to Systemic Safety Analysis (2020)

Chapter: Section 1 - Introduction

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Suggested Citation:"Section 1 - Introduction." National Academies of Sciences, Engineering, and Medicine. 2020. Guide for Quantitative Approaches to Systemic Safety Analysis. Washington, DC: The National Academies Press. doi: 10.17226/26032.
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Suggested Citation:"Section 1 - Introduction." National Academies of Sciences, Engineering, and Medicine. 2020. Guide for Quantitative Approaches to Systemic Safety Analysis. Washington, DC: The National Academies Press. doi: 10.17226/26032.
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Page 5
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Suggested Citation:"Section 1 - Introduction." National Academies of Sciences, Engineering, and Medicine. 2020. Guide for Quantitative Approaches to Systemic Safety Analysis. Washington, DC: The National Academies Press. doi: 10.17226/26032.
×
Page 6
Page 7
Suggested Citation:"Section 1 - Introduction." National Academies of Sciences, Engineering, and Medicine. 2020. Guide for Quantitative Approaches to Systemic Safety Analysis. Washington, DC: The National Academies Press. doi: 10.17226/26032.
×
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Page 8
Suggested Citation:"Section 1 - Introduction." National Academies of Sciences, Engineering, and Medicine. 2020. Guide for Quantitative Approaches to Systemic Safety Analysis. Washington, DC: The National Academies Press. doi: 10.17226/26032.
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4 Introduction 1.1 Background Highway agencies have traditionally managed their highway safety improvement process by identifying and correcting high-crash locations (“hot spots”) where concentrations of crashes and/or patterns of crashes were found. While this crash-history-based safety management approach can identify locations in need of improvement, highway safety managers have found that the search for high-crash locations often focuses safety investments at urban locations where multiple crashes in a short period occurred due to random chance. Many such short- term crash patterns would not recur, even if no improvement were made. Also, a crash-history- based safety management approach is reactive in nature as individual sites are identified for potential safety improvement only after having a documented crash history. Recently, as a complement to the crash-history-based safety management approach, highway agencies have incorporated a systemic safety management approach within their Highway Safety Improvement Program (HSIP) and other safety management programs. The systemic safety management approach utilizes either crash prediction models or rating systems to prioritize opportunities to reduce crashes. The systemic safety management approach is proactive in nature as sites can be identified for safety improvements even if they do not have a history of crashes. When applying systemic safety management procedures, agencies typically focus on reducing fatal and serious-injury crashes, consistent with U.S. national goals. Because systemic safety management procedures are newer compared to crash-history-based procedures, some agencies have experienced challenges implementing this approach within their HSIP. For example, some agencies have found it difficult to convince upper management of the potential benefits of making safety improvements to sites that do not have a documented crash history. For similar reasons, agencies have experienced challenges gaining support from the general public and stakeholders when discussing safety improvement projects programmed using a systemic safety management approach. Other challenges agencies have experienced when trying to implement systemic safety management approaches include: • Lack of software to support quantitative systemic safety analyses, • Lack of knowledge on how to best evaluate and quantify the benefits of programming safety improvements using a systemic safety management approach, and • Lack of knowledge on how best to allocate funding to support both crash-history-based and systemic safety management approaches. 1.2 Purpose and Scope of Guidance Document The purpose of this document is to help safety engineers and managers program safety improvement projects using systemic safety management approaches. Since systemic safety S E C T I O N 1

Introduction 5 management procedures are newer, many safety engineers and managers are not familiar with the concepts. In addition, systemic safety management concepts have become incorporated into more traditional roadway safety management processes so the distinction between systemic safety management approaches and more traditional approaches to roadway safety management is unclear. This document is intended to help safety engineers and managers better understand systemic safety management concepts to apply them in practice, as well as to help them better explain systemic safety management-based decisions to stakeholders. The guidance provided in this document: • Defines and distinguishes the differences between the three primary safety management approaches that highway agencies use for programming safety improvements: – Crash-history-based (i.e., hot-spot) safety management approach. – Systemic safety management approach. – Policy-based safety management approach. • Provides detailed information on existing methods and tools to conduct quantitative approaches to systemic safety analysis, focusing on three primary resources: the FHWA Systemic Safety Project Selection Tool (Preston et al., 2013) (herein referred to as the Systemic Tool), U.S. Road Assessment Program (usRAP), and Safety Analyst. • Specifies and defines appropriate applications for conducting quantitative approaches to systemic safety and provides guidance on which available software tools would be most appropriate for the applications. • Presents data needs to successfully implement quantitative approaches to systemic safety analysis and the data needs of the software tools available for conducting systemic safety analysis. • Presents current best practices of agencies implementing quantitative approaches to systemic safety analysis and their lessons learned. • Presents available resources that agencies may find useful when implementing systemic safety analyses. This guide was developed based on a review of the literature regarding safety management, conversations with highway agencies currently implementing systemic safety management approaches, the results of a recent domestic scan of state agencies using the Highway Safety Manual (HSM) for systemic safety analysis (Milton et al., 2018), and information about the Systemic Tool, usRAP, and Safety Analyst. 1.3 Relationship to Other Resources This guidance document is not meant to be all inclusive in regard to planning and imple- menting a systemic safety management approach within an agency’s HSIP and other safety management programs. The purpose of this document is to help safety engineers and managers program safety improvement projects using a systemic safety management approach. Other documents and resources include pertinent information that safety engineers and managers should have knowledge of and reference when implementing a systemic safety management approach. Several key documents and resources related to systemic safety management should be used in conjunction with this guidance document including, but not limited to, the following: • Systemic Related – The FHWA’s Systemic Safety Project Selection Tool (Preston et al., 2013) is a document that describes a process for implementing a systemic safety management approach. This resource provides step-by-step details on how to conduct systemic safety analysis and is intended for use by transportation safety practitioners at state, county, and local govern- ment agencies to plan, implement, and evaluate systemic safety improvement programs

6 Guide for Quantitative Approaches to Systemic Safety Analysis and projects that best meet their capabilities and needs. The Systemic Safety Project Selection Tool is a key resource that transportation safety practitioners should reference to better understand step-by-step details on how to conduct systemic safety analysis. – Reliability of Safety Management Methods: Systemic Safety Programs (Gross et al., 2016) describes the state-of-the-practice and latest tools to support systemic safety analysis. The objectives of this document are to: 1) raise awareness of the systemic safety management approach, 2) characterize typical projects identified and implemented through a compre- hensive safety management program, 3) demonstrate the value of integrating a systemic safety management approach into a comprehensive safety management program, and 4) provide information for allocating funds to systemic projects within a comprehensive safety management program. – NCHRP Research Report 893: Systemic Pedestrian Safety Analysis (Thomas et al., 2018) dis- cusses the use of a systemic safety management approach specifically to address pedestrian crashes. The report describes a seven-step process that includes compiling data, determin- ing contributing factors, identifying treatment sites and countermeasures, and evaluating project impacts. The report references and builds from the process described in the FHWA Systemic Tool but includes additional steps unique to pedestrian crashes. The report also describes several case studies from highway agencies using a systemic safety approach to reduce pedestrian crashes. • General Safety – The Highway Safety Manual (HSM) (AASHTO, 2010) presents procedures and informa- tion useful for implementing the six steps of the roadway safety management process. Much of the information presented in the HSM is applicable to systemic safety analysis, but the HSM does not directly distinguish systemic safety management procedures from other safety management approaches. – FHWA’s Integrating Safety in the Rural Transportation Planning Process (Waldheim et al., 2014) provides guidance to regional planning organizations (RPOs) to incorporate safety into each step of their existing planning process and to help agencies address multi- modal safety needs. Among other things, systemic safety analyses can be integrated into RPOs’ efforts to include safety considerations in the prioritization and programming processes of Transportation Improvement Programs and establish processes for prioritizing HSIP funds. • Diagnosis and Countermeasure Selection – The Contributing Factors for Focus Crash Types and Facility Types: Quick Reference Guide (Porter et al., forthcoming) assists state and local agencies interested in applying the systemic safety management approach by providing common target crash types, their associated facility types, and contributing factors for use in a systemic safety analysis. It also provides information about specific countermeasures that can be used to address the contributing factors for specific crash types on specific facility types. The target crash types, facility types, and contributing factors presented in the guide were identified from an analysis of national and state data. This guide can help agencies during the counter- measure identification and project prioritization steps of the systemic safety management approach. – FHWA’s Manual for Selecting Safety Improvements on High Risk Rural Roads (Atkinson et al., 2014) provides information on the costs and benefits of safety treatments on high risk rural roads. Agencies can use this manual to determine the safety benefits, cost effec- tiveness, applicability, and maintenance costs associated with a range of countermeasures. In addition, this manual provides information on the decision-making process necessary to identify treatments. – NCHRP Report 500: Guidance for Implementation of the AASHTO Strategic Highway Safety Plan (TRB, 2003–2009) is a compilation of 22 separate guidebooks, each focused on a

Introduction 7 specific crash type, driver behavior or demographic, or vehicle type/mode. The report series helps safety staff identify crash contributing factors and appropriate countermeasures for a given safety issue or focus crash type. – The NHTSA’s Countermeasures That Work: A Highway Safety Countermeasure Guide For State Highway Safety Offices, Ninth Edition, 2017 (Richard et al., 2018) is a resource to assist state highway safety offices (SHSOs) in selecting effective, science-based traffic safety countermeasures for major highway safety problem areas. The guide describes major strategies and countermeasures relevant to SHSOs; summarizes their uses, effectiveness, costs, and implementation time; and references the most important research summaries and individual studies. Safety strategies and countermeasures are provided to address the following issues: alcohol- and drug-impaired driving, seat belts and child restraints, speeding and speed management, distracted and drowsy driving, motorcycle safety, young drivers, older drivers, pedestrian safety, and bicycle safety. • Internet Resources – The FHWA Roadway Safety Data Program (FHWA, 2019C) provides links to resources that can help a highway agency build or strengthen an existing roadway safety data program. It is a web-based repository of safety data and analysis tools. The goal is to help agencies expand their capabilities for conducting safety analysis and evaluation. (https://safety.fhwa. dot.gov/rsdp/) – The FHWA Crash Modification Factors (CMF) Clearinghouse (FHWA, 2019A) provides a constantly updated, web-based repository of CMFs and serves as a reference for safety professionals conducting safety analyses. CMFs help safety professionals estimate the expected benefits of a given treatment on their roadway network. The repository provides the latest CMFs coming out of the research community for thousands of treatments and provides information about the study design and the reliability of the results, so practi- tioners and researchers can determine whether the CMF is applicable to their own imple- mentation of the treatment. (http://www.cmfclearinghouse.org/) – The ViDA website provides access to the usRAP ViDA software and provides general information about the various road assessment programs around the world. The website provides background information, information on how to get started with the software, training, resource documents, contract information, etc. (https://vida.irap.org) – The Safety Analyst website provides background information on the software. The web- site also provides information on data requirements, how to get started with the software, licensing details, etc. (http://www.safetyanalyst.org/) – The National Center for Rural Road Safety website provides access to the Data-Driven Safety Analysis (DDSA) Crash Tree Tool. This tool allows users to generate crash tree diagrams based on NHTSA’s Fatality Analysis Reporting System (FARS) or other crash datasets. Crash tree diagrams can be used as part of the systemic safety analysis process to help identify and select the facility types where the focus crash types most frequently occur. The crash tree can have a number of different formats, depending on agency capabilities and data availability. The Systemic Tool includes additional information about the systemic safety analysis process, including examples of crash tree diagrams. (https:// ruralsafetycenter.org/) 1.4 Outline of Guidance Document The remainder of this guidance document is organized into five additional sections and two appendices, each providing information for practitioners interested in adopting a systemic safety management approach. Section 2. Approaches to Programming Safety Improvement Projects presents the six-step safety management process described in the HSM to illustrate the three primary approaches

8 Guide for Quantitative Approaches to Systemic Safety Analysis to programming safety projects: the crash-history-based safety management approach, the systemic safety management approach, and the policy-based safety management approach. For each approach, advantages and disadvantages are discussed. Section 3. Overview of Systemic Safety Management Approaches provides a description of three general implementation approaches for systemic safety management: the use of the FHWA Systemic Tool, the use of SPFs, and the use of the usRAP methodology. In addition to describing the implementation approaches, the software tools available for systemic safety program implementation are discussed. This section also discusses the data needs for each approach; how each approach handles the steps of the safety management process; and the inputs, outputs, strengths, and limitations associated with the software tools. Section 4. Selecting the Appropriate Systemic Safety Management Approach and Software Tool provides guidance for choosing the appropriate implementation approach and software tool to implement a systemic safety management approach within an agency’s overall safety management program. The section provides a series of questions and responses to help suggest the best applications and software tools for systemic safety implementation. Section 5. Best Practices highlights the best practices of several state and local highway agencies in the form of case studies related to three main topic areas: systemic safety imple- mentation approaches, application of systemic safety by local agencies, and evaluation of systemic safety programs. This section draws on information gathered from several state and local agencies who have implemented a systemic safety program and gives further guidance on the scenarios in which systemic safety might be an appropriate approach to use as well as lessons learned from agencies who have implemented such a program. Section 6. Summary of the Systemic Safety Management Approach highlights the types of target crashes, facility types, and countermeasures that have been addressed through systemic safety management and use of three approaches to implementing systemic safety management: application of the FHWA Systemic Tool methodology, application of SPFs, and application of the usRAP methodology using the associated ViDA software. Bibliography provides citations for the resources referenced in this guide. Appendix A is a two-page flyer intended to serve as marketing material to promote the implementation of systemic safety management approaches. The flyer explains the concept of systemic safety analysis, tools and resources available to implement systemic safety, and the benefits of systemic safety analysis. Appendix B is a two-page document intended to highlight the benefits of systemic safety analysis to decision makers. Safety engineers and program managers will be able to use this resource to promote systemic safety management approaches to decision makers.

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Traditional approaches to safety have focused on identifying high-crash locations and implementing projects to address predominant concerns at these locations. The systemic approach to safety is a method of safety management that typically involves lower unit cost safety improvements that are widely implemented based on high risk factors.

The TRB National Cooperative Highway Research Program's NCHRP Research Report 955: Guide for Quantitative Approaches to Systemic Safety Analysis provides guidance to state departments of transportation (DOTs) and other transportation agencies on how to apply a systemic safety management approach for identifying safety improvement projects.

Material associated with the report includes NCHRP Web-Only Document 285: Developing a Guide for Quantitative Approaches to Systemic Safety Analysis and a PowerPoint of the summary of project findings and future research needs.

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