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2020 N A T I O N A L C O O P E R A T I V E H I G H W A Y R E S E A R C H P R O G R A M NCHRP RESEARCH REPORT 955 Guide for Quantitative Approaches to Systemic Safety Analysis Darren J. Torbic Jessica M. Hutton MRIGlobal Kansas City, MO Kim Kolody Silverman Jacobs Chicago, IL Douglas W. Harwood HaRwood Road safety, llc Leawood, KS Subscriber Categories Highways â¢ Safety and Human Factors Research sponsored by the American Association of State Highway and Transportation Officials in cooperation with the Federal Highway Administration
NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM Systematic, well-designed, and implementable research is the most effective way to solve many problems facing state departments of transportation (DOTs) administrators and engineers. Often, highway problems are of local or regional interest and can best be studied by state DOTs individually or in cooperation with their state universities and others. However, the accelerating growth of highway transporta- tion results in increasingly complex problems of wide interest to high- way authorities. These problems are best studied through a coordinated program of cooperative research. Recognizing this need, the leadership of the American Association of State Highway and Transportation Officials (AASHTO) in 1962 ini- tiated an objective national highway research program using modern scientific techniquesâthe National Cooperative Highway Research Program (NCHRP). NCHRP is supported on a continuing basis by funds from participating member states of AASHTO and receives the full cooperation and support of the Federal Highway Administration (FHWA), United States Department of Transportation, under Agree- ment No. 693JJ31950003. The Transportation Research Board (TRB) of the National Academies of Sciences, Engineering, and Medicine was requested by AASHTO to administer the research program because of TRBâs recognized objectivity and understanding of modern research practices. TRB is uniquely suited for this purpose for many reasons: TRB maintains an extensive com- mittee structure from which authorities on any highway transportation subject may be drawn; TRB possesses avenues of communications and cooperation with federal, state, and local governmental agencies, univer- sities, and industry; TRBâs relationship to the National Academies is an insurance of objectivity; and TRB maintains a full-time staff of special- ists in highway transportation matters to bring the findings of research directly to those in a position to use them. The program is developed on the basis of research needs iden- tified by chief administrators and other staff of the highway and transportation departments, by committees of AASHTO, and by the FHWA. Topics of the highest merit are selected by the AASHTO Special Committee on Research and Innovation (R&I), and each year R&Iâs recommendations are proposed to the AASHTO Board of Direc- tors and the National Academies. Research projects to address these topics are defined by NCHRP, and qualified research agencies are selected from submitted proposals. Administration and surveillance of research contracts are the responsibilities of the National Academies and TRB. The needs for highway research are many, and NCHRP can make significant contributions to solving highway transportation problems of mutual concern to many responsible groups. The program, however, is intended to complement, rather than to substitute for or duplicate, other highway research programs. Published research reports of the NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM are available from Transportation Research Board Business Office 500 Fifth Street, NW Washington, DC 20001 and can be ordered through the Internet by going to https://www.nationalacademies.org and then searching for TRB Printed in the United States of America NCHRP RESEARCH REPORT 955 Project 17-77 ISSN 2572-3766 (Print) ISSN 2572-3774 (Online) ISBN 978-0-309-67355-6 Library of Congress Control Number 2020947798 Â© 2020 National Academy of Sciences. All rights reserved. COPYRIGHT INFORMATION Authors herein are responsible for the authenticity of their materials and for obtaining written permissions from publishers or persons who own the copyright to any previously published or copyrighted material used herein. Cooperative Research Programs (CRP) grants permission to reproduce material in this publication for classroom and not-for-profit purposes. Permission is given with the understanding that none of the material will be used to imply TRB, AASHTO, FAA, FHWA, FTA, GHSA, NHTSA, or TDC endorsement of a particular product, method, or practice. It is expected that those reproducing the material in this document for educational and not-for-profit uses will give appropriate acknowledgment of the source of any reprinted or reproduced material. For other uses of the material, request permission from CRP. NOTICE The research report was reviewed by the technical panel and accepted for publication according to procedures established and overseen by the Transportation Research Board and approved by the National Academies of Sciences, Engineering, and Medicine. The opinions and conclusions expressed or implied in this report are those of the researchers who performed the research and are not necessarily those of the Transportation Research Board; the National Academies of Sciences, Engineering, and Medicine; the FHWA; or the program sponsors. The Transportation Research Board; the National Academies of Sciences, Engineering, and Medicine; and the sponsors of the National Cooperative Highway Research Program do not endorse products or manufacturers. Trade or manufacturersâ names appear herein solely because they are considered essential to the object of the report.
The National Academy of Sciences was established in 1863 by an Act of Congress, signed by President Lincoln, as a private, non- governmental institution to advise the nation on issues related to science and technology. Members are elected by their peers for outstanding contributions to research. Dr. Marcia McNutt is president. The National Academy of Engineering was established in 1964 under the charter of the National Academy of Sciences to bring the practices of engineering to advising the nation. Members are elected by their peers for extraordinary contributions to engineering. Dr. John L. Anderson is president. The National Academy of Medicine (formerly the Institute of Medicine) was established in 1970 under the charter of the National Academy of Sciences to advise the nation on medical and health issues. Members are elected by their peers for distinguished contributions to medicine and health. Dr. Victor J. Dzau is president. The three Academies work together as the National Academies of Sciences, Engineering, and Medicine to provide independent, objective analysis and advice to the nation and conduct other activities to solve complex problems and inform public policy decisions. The National Academies also encourage education and research, recognize outstanding contributions to knowledge, and increase public understanding in matters of science, engineering, and medicine. Learn more about the National Academies of Sciences, Engineering, and Medicine at www.nationalacademies.org. The Transportation Research Board is one of seven major programs of the National Academies of Sciences, Engineering, and Medicine. The mission of the Transportation Research Board is to provide leadership in transportation improvements and innovation through trusted, timely, impartial, and evidence-based information exchange, research, and advice regarding all modes of transportation. The Boardâs varied activities annually engage about 8,000 engineers, scientists, and other transportation researchers and practitioners from the public and private sectors and academia, all of whom contribute their expertise in the public interest. The program is supported by state transportation departments, federal agencies including the component administrations of the U.S. Department of Transportation, and other organizations and individuals interested in the development of transportation. Learn more about the Transportation Research Board at www.TRB.org.
C O O P E R A T I V E R E S E A R C H P R O G R A M S AUTHOR ACKNOWLEDGMENTS Development of this guidance document was performed under National Cooperative Highway Research Program (NCHRP) Project 17â77, âGuide for Quantitative Approaches to Systemic Safety Analysis.â This guidance document was prepared by Dr. Darren J. Torbic and Ms. Jessica M. Hutton of MRIGlobal, Ms. Kimberly Kolody Silverman of Jacobs, and Mr. Douglas W. Harwood of Harwood Road Safety, LLC. For additional details on the research that went into the development of this guidance document, refer to NCHRP Web-Only Document 285: Developing a Guide for Quantitative Approaches to Systemic Safety Analysis. The authors wish to thank the following highway agencies for their assistance in this research: State Agencies: Local/County Agencies: â¢ Kentucky â¢ Thurston County (WA) â¢ Maine â¢ Marion County (OR) â¢ Minnesota â¢ City of Salem (OR) â¢ Oregon â¢ Rhode Island â¢ Texas â¢ Utah â¢ Washington CRP STAFF FOR NCHRP RESEARCH REPORT 955 Christopher J. Hedges, Director, Cooperative Research Programs Lori L. Sundstrom, Deputy Director, Cooperative Research Programs Dianne S. Schwager, Senior Program Officer Jarrel McAfee, Senior Program Assistant Eileen P. Delaney, Director of Publications Natalie Barnes, Associate Director of Publications NCHRP PROJECT 17-77 PANEL Field of TrafficâArea of Safety Matthew T. Enders, Washington State Department of Transportation, Olympia, WA (Chair) Andrew Hershel Ceifetz, WSP, Detroit, MI Tracy A. Lovell, Kentucky Transportation Cabinet, Frankfort, KY Darren V. McDaniel, Texas Department of Transportation, Austin, TX Kelvin Saldanha, WSP UK Ltd, Inc., Birmingham, UK Erin Schoon, Wisconsin Department of Transportation, Milwaukee, WI Timothy J. Sheehan, Illinois Department of Transportation (Retired), Springfield, IL Xiaoduan Sun, University of Louisiana at Lafayette, Lafayette, LA Giri Venkiteela, New Jersey Department of Transportation, Trenton, NJ Karen Scurry, FHWA Liaison Kelly K. Hardy, AASHTO Liaison Bernardo B. Kleiner, TRB Liaison
NCHRP Research Report 955 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. The report focuses on crash types that occur with high frequency across the roadway network but are not concentrated at individual locations, which tend to be overlooked when ranking sites using a traditional crash-history-based safety management approach. The guide and training materials will be of immediate use to safety practitioners in state DOTs, Metropolitan Planning Orga- nizations, and local agencies. Traditional approaches to safety have focused on identifying high-crash locations and constructing 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. While there is considerable interest from practitioners for quantitative approaches to systemic safety analysis, to date there is limited knowledge about the methods and tools available to agencies seeking to implement quantitative approaches to systemic safety analysis to make data-driven decisions. The systemic approach was not included in the first edition of the Highway Safety Manual. Therefore, to be consistent with methods that are capable of adequately considering safety performance and risk factors (e.g., crash frequency and exposure), this research addressed a need for guidance and recommendations to integrate quantitative systemic safety analysis methods and tools into existing safety management processes. Under NCHRP Project 17â77, âGuide for Quantitative Approaches to Systemic Safety Analysis,â MRIGlobal was asked to develop a guide and training materials for safety prac- titioners to better understand, use, and implement quantitative approaches to systemic safety analysis. In addition to NCHRP Research Report 955: Guide for Quantitative Approaches to Systemic Safety Analysis, this research produced (1) Web-Only Document 285: Developing a Guide for Quantitative Approaches to Systemic Safety Analysis and (2) a PowerPoint presentation titled, âSummary of Project Findings and Recommendations for Future Research.â These additional resources are available from the TRB website (TRB.org) by searching for âNCHRP Research Report 955.â F O R E W O R D By Dianne S. Schwager Staff Officer Transportation Research Board
1 Summary 4 Section 1 Introduction 4 1.1 Background 4 1.2 Purpose and Scope of Guidance Document 5 1.3 Relationship to Other Resources 7 1.4 Outline of Guidance Document 9 Section 2 Approaches to Programming Safety Improvement Projects 9 2.1 Six-Step Approach to Roadway Safety Management 13 2.2 Crash-History-Based Safety Management Approach 14 2.3 Systemic Safety Management Approach 17 2.4 Policy-Based Safety Management Approach 18 2.5 Summary 20 Section 3 Overview of Systemic Safety Management Approaches 20 3.1 Application of the FHWA Systemic Safety Project Selection Tool Methodology 30 3.2 Application of Safety Performance Functions (SPFs) for Systemic Safety Management 46 3.3 Application of U.S. Road Assessment Program (usRAP) Methodology and ViDA Software 52 3.4 Summary 54 Section 4 Selecting the Appropriate Systemic Safety Management Approach and Software Tool 61 Section 5 Best Practices 61 5.1 Applications of the Three Primary Systemic Safety Program Implementation Approaches 76 5.2 Local Applications of Systemic Safety 81 5.3 Evaluation of Systemic Safety Management Programs 88 Section 6 Summary of the Systemic Safety Management Approach 91 Bibliography A-1 Appendix A Flyer to Promote the Implementation of Systemic Safety Analysis B-1 Appendix B Document Highlighting Benefits of Systemic Safety Analysis to Decision Makers C O N T E N T S Note: Photographs, figures, and tables in this report may have been converted from color to grayscale for printing. The electronic version of the report (posted on the web at www.trb.org) retains the color versions.