Diagnostic Assessment and Countermeasure Selection: A Toolbox for Traffic Safety Practitioners (2024)
Chapter: Front Matter
Diagnostic Assessment and
Countermeasure Selection
A TOOLBOX FOR TRAFFIC SAFETY PRACTITIONERS
TRANSPORTATION RESEARCH BOARD 2024 EXECUTIVE COMMITTEE*
OFFICERS
CHAIR: Carol A. Lewis, Professor, Transportation Studies, Texas Southern University, Houston
VICE CHAIR: Leslie S. Richards, General Manager, Southeastern Pennsylvania Transportation Authority (SEPTA), Philadelphia
EXECUTIVE DIRECTOR: Victoria Sheehan, Transportation Research Board, Washington, DC
MEMBERS
Michael F. Ableson, CEO, Arrival Automotive–North America, Detroit, MI
James F. Albaugh, President and CEO, The Boeing Company (retired), Scottsdale, AZ
Carlos M. Braceras, Executive Director, Utah Department of Transportation, Salt Lake City
Douglas C. Ceva, Vice President, Customer Lead Solutions, Prologis, Inc., Jupiter, FL
Nancy Daubenberger, Commissioner of Transportation, Minnesota Department of Transportation, St. Paul
Marie Therese Dominguez, Commissioner, New York State Department of Transportation, Albany
Garrett Eucalitto, Commissioner, Connecticut Department of Transportation, Newington
Chris T. Hendrickson, Hamerschlag University Professor of Engineering Emeritus, Carnegie Mellon University, Pittsburgh, PA
Randell Iwasaki, President and CEO, Iwasaki Consulting Services, Walnut Creek, CA
Ashby Johnson, Executive Director, Capital Area Metropolitan Planning Organization (CAMPO), Austin, TX
Joel M. Jundt, Secretary of Transportation, South Dakota Department of Transportation, Pierre
Hani S. Mahmassani, W.A. Patterson Distinguished Chair in Transportation; Director, Transportation Center, Northwestern University, Evanston, IL
Scott C. Marler, Director, Iowa Department of Transportation, Ames
Ricardo Martinez, Adjunct Professor of Emergency Medicine, Emory University School of Medicine, Decatur, GA
Michael R. McClellan, Vice President, Strategic Planning, Norfolk Southern Corporation, Norfolk, VA
Russell McMurry, Commissioner, Georgia Department of Transportation, Atlanta
Craig E. Philip, Research Professor and Director, VECTOR, Department of Civil and Environmental Engineering, Vanderbilt University, Nashville, TN
Steward T.A. Pickett, Distinguished Senior Scientist, Cary Institute of Ecosystem Studies, Millbrook, NY
Susan A. Shaheen, Professor and Co-director, Transportation Sustainability Research Center, University of California, Berkeley
Marc Williams, Executive Director, Texas Department of Transportation, Austin
EX OFFICIO MEMBERS
Michael R. Berube, Deputy Assistant Secretary for Sustainable Transportation, U.S. Department of Energy, Washington, DC
Shailen Bhatt, Administrator, Federal Highway Administration, U.S. Department of Transportation, Washington, DC
Amit Bose, Administrator, Federal Railroad Administration, Washington, DC
Tristan Brown, Deputy Administrator, Pipeline and Hazardous Materials Safety Administration, U.S. Department of Transportation, Washington, DC
Steven Cliff, Executive Officer, California Air Resources Board, Sacramento
Rand Ghayad, Senior Vice President, Association of American Railroads, Washington, DC
LeRoy Gishi, Chief, Division of Transportation, Bureau of Indian Affairs, U.S. Department of the Interior, Germantown, MD
William H. Graham, Jr. (Major General, U.S. Army), Deputy Commanding General for Civil and Emergency Operations, U.S. Army Corps of Engineers, Washington, DC
Robert C. Hampshire, Deputy Assistant Secretary for Research and Technology, U.S. Department of Transportation, Washington, DC
Sue Lawless, Acting Deputy Administrator, Federal Motor Carrier Safety Administration, Washington, DC
Niloo Parvashtiani, Engineer, Mobility Consultant Solutions, Iteris Inc., Fairfax, VA, and Chair, TRB Young Members Coordinating Council
Sophie Shulman, Acting Administrator, National Highway Traffic Safety Administration, Washington, DC
Karl Simon, Director, Transportation and Climate Division, U.S. Environmental Protection Agency, Washington, DC
Paul P. Skoutelas, President and CEO, American Public Transportation Association, Washington, DC
Polly Trottenberg, Deputy Secretary of Transportation and Acting Administrator, Federal Aviation Administration, U.S. Department of Transportation, Washington, DC
Jim Tymon, Executive Director, American Association of State Highway and Transportation Officials, Washington, DC
Veronica Vanterpool, Acting Administrator, Federal Transit Administration, Washington, DC
__________________
* Membership as of May 2024.
NATIONAL COOPERATIVE RESEARCH PROGRAM
NCHRP RESEARCH REPORT 1111
BEHAVIORAL TRAFFIC SAFETY COOPERATIVE RESEARCH PROGRAM
BTSCRP RESEARCH REPORT 12
Diagnostic Assessment and
Countermeasure Selection
A TOOLBOX FOR TRAFFIC SAFETY PRACTITIONERS
John L. Campbell
Liberty Hoekstra-Atwood
EXPONENT
Bellevue, WA
Chris Monk
EXPONENT
Washington, DC
Audra K. Fraser
EXPONENT
Irvine, CA
Darren J. Torbic
Ingrid B. Potts
TEXAS A&M UNIVERSITY
TEXAS TRANSPORTATION INSTITUTE
College Station, TX
Subscriber Categories
Highways • Operations and Traffic Management • Safety and Human Factors
Research sponsored by the American Association of State Highway and Transportation Officials
in cooperation with the Federal Highway Administration and under the direction and
oversight of the Governors Highway Safety Association
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 transportation results in increasingly complex problems of wide interest to highway 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 initiated an objective national highway research program using modern scientific techniques—the 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 Agreement 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 TRB’s recognized objectivity and understanding of modern research practices. TRB is uniquely suited for this purpose for many reasons: TRB maintains an extensive committee 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, universities, and industry; TRB’s relationship to the National Academies is an insurance of objectivity; and TRB maintains a full-time staff of specialists 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 identified 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&I’s recommendations are proposed to the AASHTO Board of Directors 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.
NCHRP RESEARCH REPORT 1111
Project 22-45
ISSN 2572-3766 (Print)
ISSN 2572-3774 (Online)
ISBN 978-0-309-70997-2
Library of Congress Control Number 2024940434
© 2024 by the National Academy of Sciences. National Academies of Sciences, Engineering, and Medicine and the graphical logo are trademarks of the 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, APTA, FAA, FHWA, FTA, GHSA, or NHTSA 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 does not develop, issue, or publish standards or specifications. The Transportation Research Board manages applied research projects which provide the scientific foundation that may be used by Transportation Research Board sponsors, industry associations, or other organizations as the basis for revised practices, procedures, or specifications.
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 manufacturers’ names or logos appear herein solely because they are considered essential to the object of the report.
Published research reports of the
NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM
are available from
National Academies Press
500 Fifth Street, NW, Keck 360
Washington, DC 20001
(800) 624-6242
and can be ordered through the Internet by going to
https://nap.nationalacademies.org
Printed in the United States of America
BEHAVIORAL TRAFFIC SAFETY COOPERATIVE RESEARCH PROGRAM
Since the widespread introduction of motor vehicles more than a century ago, crashes involving their operation remain a significant public health concern. While there have been enormous improvements in highway design and construction, as well as motor vehicle safety, which have been instrumental in lowering the rate of crashes per million miles in the United States, more than 35,000 people die every year in motor vehicle crashes. In far too many cases, the root causes of the crashes are the unsafe behaviors of motor vehicle operators, cyclists, and pedestrians. Understanding human behaviors and developing effective countermeasures to unsafe ones is difficult and remains a major weakness in our traffic safety efforts.
The Behavioral Traffic Safety Cooperative Research Program (BTSCRP) develops practical solutions to save lives, prevent injuries, and reduce costs of road traffic crashes associated with unsafe behaviors. BTSCRP is a forum for coordinated and collaborative research efforts. It is managed by the Transportation Research Board (TRB) under the direction and oversight of the Governors Highway Safety Association (GHSA) with funding provided by the National Highway Traffic Safety Administration (NHTSA). Funding for the program was originally established in Moving Ahead for Progress in the 21st Century (MAP-21), Subsection 402(c), which created the National Cooperative Research and Evaluation Program (NCREP). Fixing America’s Surface Transportation (FAST) Act continued the program. In 2017, GHSA entered into an agreement with TRB to manage the research activities, with the program name changed to Behavioral Traffic Safety Cooperative Research Program. The GHSA Executive Board serves as the governing board for the BTSCRP. The Board consists of officers, representatives of the 10 NHTSA regions, and committee and task force chairs. The Research Committee Chair appoints committee members who recommend projects for funding and provide oversight for the activities of BTSCRP. Its ultimate goal is to oversee a quality research program that is committed to addressing research issues facing State Highway Safety Offices. The Executive Board meets annually to approve research projects. Each selected project is assigned to a panel, appointed by TRB, which provides technical guidance and counsel throughout the life of the project. The majority of panel members represent the intended users of the research projects and have an important role in helping to implement the results. BTSCRP produces a series of research reports and other products such as guidebooks for practitioners. Primary emphasis is placed on disseminating BTSCRP results to the intended users of the research: State Highway Safety Offices and their constituents.
BTSCRP RESEARCH REPORT 12
Project BTS-14
ISSN 2766-5976 (Print)
ISSN 2766-5984 (Online)
ISBN 978-0-309-70997-2
Library of Congress Control Number 2024940434
© 2024 by the National Academy of Sciences. National Academies of Sciences, Engineering, and Medicine and the graphical logo are trademarks of the 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, APTA, FAA, FHWA, FTA, GHSA, or NHTSA 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; or the program sponsors.
The Transportation Research Board does not develop, issue, or publish standards or specifications. The Transportation Research Board manages applied research projects which provide the scientific foundation that may be used by Transportation Research Board sponsors, industry associations, or other organizations as the basis for revised practices, procedures, or specifications.
The Transportation Research Board; the National Academies of Sciences, Engineering, and Medicine; and the sponsors of the Behavioral Traffic Safety Cooperative Research Program do not endorse products or manufacturers. Trade or manufacturers’ names or logos appear herein solely because they are considered essential to the object of the report.
Published research reports of the
BEHAVIORAL TRAFFIC SAFETY COOPERATIVE RESEARCH PROGRAM
are available from
National Academies Press
500 Fifth Street, NW, Keck 360
Washington, DC 20001
(800) 624-6242
and can be ordered through the Internet by going to
https://nap.nationalacademies.org
Printed in the United States of America
This page intentionally left blank.
The National Academy of Sciences was established in 1863 by an Act of Congress, signed by President Lincoln, as a private, nongovernmental 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 program divisions of the National Academies of Sciences, Engineering, and Medicine. The mission of the Transportation Research Board is to mobilize expertise, experience, and knowledge to anticipate and solve complex transportation-related challenges. The Board’s varied activities annually engage about 8,500 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.
COOPERATIVE RESEARCH PROGRAMS
CRP STAFF FOR NCHRP RESEARCH REPORT 1111/BTSCRP RESEARCH REPORT 12
Waseem Dekelbab, Deputy Director, Cooperative Research Programs, and Manager, National Cooperative Highway Research Program
Richard A. Retting, Senior Program Officer
Dajaih Bias-Johnson, Senior Program Assistant
Natalie Barnes, Director of Publications
Heather DiAngelis, Associate Director of Publications
NCHRP PROJECT 22-45/BTSCRP PROJECT BTS-14 PANEL
Field of Design—Area of Vehicle Barrier Systems
Priyanka Alluri, Florida International University, Miami, FL
John C. Milton, Washington State Department of Transportation, Olympia, WA
Sung Yoon Park, Maryland State Highway Administration, Hanover, MD
Bernadette Estioko Phelan, Phelan International LLC, Scottsdale, AZ
Robert A. Skehan, Maine Department of Transportation, Augusta, ME
John S. Tomlinson, Idaho Transportation Department, Boise, ID
Christopher J. Turner, Kansas Third District Judicial Court, Topeka, KS
Dustin R. Witt, South Dakota Department of Transportation, Pierre, SD
Jonathan S. Wood, Iowa State University, Ames, IA
Karen Scurry, FHWA Liaison
Derek A. Troyer, FHWA Liaison
Kelly K. Hardy, AASHTO Liaison
Bernardo B. Kleiner, TRB Liaison
AUTHOR ACKNOWLEDGMENTS
The research reported herein was performed under NCHRP Project 22-45/BTSCRP Project BTS-14 by Exponent, with the Texas Transportation Institute (TTI) of Texas A&M University serving as a research partner.
FOREWORD
By Richard A. Retting
Staff Officer
Transportation Research Board
NCHRP Research Report 1111/BTSCRP Research Report 12 presents a toolbox to help highway safety practitioners diagnose contributing factors leading to crashes for use in selecting appropriate countermeasures. To develop this toolbox, the research team conducted a systematic literature review; developed comprehensive evaluation and analysis procedures, methods, and tools; and conducted a workshop to demonstrate the use of the draft toolbox to receive feedback from practitioners. This publication will be of interest to state departments of transportation and other stakeholders concerned with diagnosing contributing factors leading to crashes for use in selecting appropriate countermeasures.
Successful safety management practices require a thorough understanding of factors contributing to motor vehicle crashes. Continuous advancements in data-driven safety analysis, as well as the countermeasures and technologies available to address crashes, create challenges in maintaining a safety workforce proficient in the state of the practice. In many cases, agencies continue to use approaches such as descriptive statistics and anecdotal information to perform the diagnostic assessment without a thorough understanding of the expectations for a given context or road type. Additionally, choosing an effective countermeasure requires an examination of the human factors, behavioral factors, future development, prevailing or predicted crash types, and mix of road users to determine the most appropriate treatments to apply. Doing so allows the selected countermeasure to reduce crashes to the greatest extent possible. However, in many cases, practitioners have limited understanding of the potential for a treatment selection to affect other road users. A better understanding of these relationships and trade-offs could inform design choices and ultimately result in safer roadways for all road users.
Under NCHRP Project 22-45/BTSCRP Project BTS-14, Exponent was asked to develop a toolbox for diagnosing contributing factors leading to crashes that will aid practitioners in selecting appropriate countermeasures in modally diverse contexts. The research team (1) performed a detailed review and assessment of the research literature related to crash diagnosis, factors leading to crashes, and countermeasure selection; (2) developed comprehensive evaluation and analysis procedures, methods, and tools to support understanding and analysis of crash contributing factors; (3) conducted a workshop to demonstrate the use of the new and/or enhanced methods and tools, and to receive feedback from practitioners; and (4) developed a toolbox to help highway safety practitioners diagnose contributing factors leading to crashes for use in selecting appropriate countermeasures.
In addition to this report, the following deliverables are available on the National Academies Press website (nap.nationalacademies.org) by searching for NCHRP Research Report 1111/BTSCRP Research Report 12:
- A technical memorandum on implementation of research findings and products,
- A PowerPoint presentation, and
- A conduct of research report.
CONTENTS
1.4 Evaluation as a Key Element of Diagnostic Assessment and Countermeasure Selection
1.5 Trade-offs in a Multimodal Transportation Network
1.6 Summary of the Remainder of This Toolbox
Chapter 2 What Causes Roadway Crashes?
2.3 Key Concepts: Contributing Factors to Roadway Crashes
2.4 Diagnostic Questions Related to the Contributing Factors to Roadway Crashes
Chapter 3 Diagnostic Assessment in the Safe System>
3.3 Key Concepts: A Safe System Approach to Diagnostic Assessment
3.4 A General Tool and Process for Diagnostic Assessment
Chapter 4 Distinguishing Between Human Factors Issues and Aberrant Driver Behaviors
Chapter 5 Perception-Response Time as a Contributing Factor to Crashes
5.3 Key Concepts: How PRT Can Impact Safety Performance
5.4 Diagnostic Questions Related to PRT
Chapter 7 The Role of Visibility in Road User Behavior
7.3 Key Concepts: What Are the Relationships Between Visibility, Vision, and Attention?
7.4 Example of How Visibility Can Impact Driver Performance
7.5 Diagnostic Questions Related to Visibility
Chapter 8 Task Demand as a Contributing Factor to Crashes
8.2 Background and Key Concepts
8.3 Diagnostic Questions Regarding Demand and Workload
Chapter 9 Linking Contributing Factors to Countermeasures
Chapter 10 Decision Trees to Support Countermeasure Selection
10.4 Rural Multilane Undivided Segments
10.5 Rural Multilane Divided Segments
10.7 Urban Multilane Undivided Segments
10.8 Urban Multilane Divided Segments
10.9 Rural and Urban Signalized Intersections
10.10 Rural and Urban Unsignalized Intersections
Chapter 11 Procedures for Assessing Road User Demands
11.1 Quantifying Workload in Driving Tasks
11.3 Methods for Assessing Driver Workload
11.4 Working Example of Approach 2: Analytical Inventory of Demands based on Roadway Features
Chapter 12 Blank Templates and Worksheets
Appendix Summary of Current Diagnostic Assessment and Countermeasure Selection Tools for Crashes
