TRANSPORTATION RESEARCH BOARD 2025 EXECUTIVE COMMITTEE*

OFFICERS

CHAIR: Leslie S. Richards, Professor of Practice, University of Pennsylvania, Philadelphia

VICE CHAIR: Joel M. Jundt, Secretary of Transportation, South Dakota Department of Transportation, Pierre

EXECUTIVE DIRECTOR: Victoria Sheehan, Transportation Research Board, Washington, DC

MEMBERS

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

Andrew Fremier, Executive Director, Metropolitan Transportation Commission, San Francisco, CA

Martha Grabowski, Professor Emerita, Information Systems, Le Moyne College, Madden College of Business & Economics, Cazenovia, NY

Randell Iwasaki, President and CEO, Iwasaki Consulting Services, Walnut Creek, CA

Carol A. Lewis, Professor, Transportation Studies, Texas Southern University, Houston

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

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

Steven G. Bradbury, Deputy Secretary, U.S. Department of Transportation, Washington, DC

Steven Cliff, Executive Officer, California Air Resources Board, Sacramento

LeRoy Gishi, Chief, Division of Transportation, Bureau of Indian Affairs, U.S. Department of the Interior, Germantown, MD

Firas Ibrahim, Director, Office of Research, Development, and Technology, Office of the Assistant Secretary for Research and Technology (OST-R), Washington, DC

Jason Kelly, Deputy Commanding General for Civil Works and Emergency Operations, U.S. Army Corps of Engineers, Washington, DC

Sandra Knight, President, WaterWonks, LLC, Washington, DC

Ben Kochman, Acting Administrator, Pipeline and Hazardous Materials Safety Administration, Washington, DC

Zahra “Niloo” Parvinashtiani, Engineer, Mobility Consultant Solutions, Iteris Inc., Fairfax, VA, and Chair, TRB Young Members Coordinating Council

Chris Rocheleau, Acting Administrator, Federal Aviation Administration, Washington, DC

Gloria Shepherd, Acting Deputy Administrator, Federal Highway 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

Jim Tymon, Executive Director, American Association of State Highway and Transportation Officials, Washington, DC

___________________

^* Membership as of May 2025.

NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM

A Guide to Applying the Safe System Approach to Transportation Planning, Design, and Operations

Seth LaJeunesse
Daniel Gelinne
Wesley Kumfer
Katherine Harmon
Laura Sandt
Jonathon Weisenfeld
THE UNIVERSITY OF NORTH CAROLINA HIGHWAY SAFETY RESEARCH CENTER
UNIVERSITY OF NORTH CAROLINA AT CHAPEL HILL
Chapel Hill, NC

Tabitha Combs
DEPARTMENT OF CITY AND REGIONAL PLANNING,
UNIVERSITY OF NORTH CAROLINA AT CHAPEL HILL
Chapel Hill, NC

Kendra Schenk
Jeremy VanVleet
BURGESS & NIPLE
Columbus, OH

Nick Falbo
Narayan Donaldson
MOBYCON
Ottawa, ON, Canada

Timothy E. Barnett
Brundidge, AL

Alan Dellapenna
Wake Forest, NC

Subscriber Categories
Operations and Traffic Management • Policy • 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 department of transportation (DOT) 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.

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, the FHWA, 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 oversight of research contracts are the responsibilities of NCHRP.

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 1135

Project 17-101
ISSN 2572-3766 (Print)
ISSN 2572-3774 (Online)
ISBN 978-0-309-99350-0
Library of Congress Control Number 2025941355
Digital Object Identifier: 10.17226/29147

© 2025 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 originality and accuracy 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.

The National Academy of Sciences (NAS) grants permission to reproduce written material in this publication for classroom and non-commercial purposes subject to the rights of any third parties and appropriate attribution. Permission is given with the understanding that none of the material will be used to imply NAS, TRB, AASHTO, APTA, FAA, FHWA, FTA, GHSA, or NHTSA endorsement of a particular product, method, or practice. For other uses of the written material, users must request permission from the National Academies Press.

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.

This material is based upon work supported by the FHWA under Agreement No. 693JJ32350025. Any opinions, findings, and conclusions or recommendations expressed or implied in this document 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

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. Tsu-Jae Liu 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 departments of transportation, 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 1135

Monique R. Evans, Director, Cooperative Research Programs

Waseem Dekelbab, Deputy Director, Cooperative Research Programs, and Manager, National Cooperative Highway Research Program

David M. Jared, Senior Program Officer

Dajaih Bias-Johnson, Senior Program Assistant

Natalie Barnes, Director of Publications

Heather DiAngelis, Associate Director of Publications

Kristin C. Sawyer, Editor

NCHRP PROJECT 17-101 PANEL
Field of Traffic—Area of Safety

Bonnie S. Polin, Massachusetts Department of Transportation, Boston, MA (Chair)

Angshuman Guin, Georgia Institute of Technology, Atlanta, GA

Susan B. Herbel, SBH Consult, Fort Meyers, FL

Margaret Mary Herrera, Maricopa Association of Governments, Phoenix, AZ

Ken Johnson, Minnesota Department of Transportation, Roseville, MN

Daniel J. Magri, Buchart Horn, Inc., Baton Rouge, LA

Mark A. Doctor, FHWA Liaison

Kelly K. Hardy, AASHTO Liaison

Bernardo B. Kleiner, TRB Liaison

AUTHOR ACKNOWLEDGMENTS

The authors acknowledge the respondents to the research team’s practitioner survey and the focus group participants. The insights provided by the survey respondents and focus group participants rendered the guidance provided herein far more practical and useful than had they not contributed to this effort.

FOREWORD

By David M. Jared
Staff Officer
Transportation Research Board

NCHRP Research Report 1135: A Guide to Applying the Safe System Approach to Transportation Planning, Design, and Operations presents information for applying the Safe System approach among state departments of transportation (DOTs) and other transportation agencies. Based on extensive stakeholder outreach, including practitioner focus groups, the guide covers six domains of practice in transportation safety that users can draw from based on their organizational interests, competencies, and safety-oriented goals. This guide should be of particular use to state DOTs and any other transportation agency seeking to provide resources for transportation planners, designers, and operations managers to implement Safe System principles and make the systems under their jurisdictions safer.

The Safe System approach is a holistic approach that provides a framework for making the national transportation system safer. It is based on building and reinforcing multiple layers of protection to prevent crashes from happening and minimize the harm caused when crashes occur. This safety approach differs from conventional ones because it focuses on human vulnerability and creates a system with many redundancies to protect all transportation users. Despite increased interest in the Safe System approach, few guidelines exist for transportation planners, designers, and operations managers for implementing a safe system. To fully implement a Safe System approach, infrastructure design, vehicle design, policies and law, recognition of shared safety responsibility, road-user behavior, and public culture—all of which will require some degree of change—must be addressed. Research was needed to begin providing resources for transportation planners, designers, and operations managers to consult during safety problem identification, project development, and countermeasure selection.

Under NCHRP Project 17-101, “Applying the Safe System Approach to Transportation Planning, Design, and Operations in the United States,” the University of North Carolina at Chapel Hill was asked to develop materials that would enable a range of professionals and organizations to adopt and implement the Safe System approach in their work. Using extensive outreach to a variety of safety stakeholders, the research team identified strategies, practices, and policies for implementing the Safe System approach in the United States then modularized them using six domains of practice integral to implementation. The resultant guide provides safety teams with the foregoing resources and a Safe System Strategy Implementation Self-Assessment designed to offer insight into teams’ progress in implementing Safe System–aligned strategies across domains of practice.

In addition to NCHRP Research Report 1135, the following three deliverables can be found on the National Academies Press website (nap.nationalacademies.org) by searching for NCHRP Research Report 1135: A Guide to Applying the Safe System Approach to Transportation Planning, Design, and Operations:

• A conduct of research report summarizing the entire effort, available as NCHRP Web-Only Document 413: Applying the Safe System Approach to Transportation Planning, Design, and Operations
• A plan that identifies mechanisms and channels for communicating and implementing this research
• A PowerPoint presentation introducing NCHRP Research Report 1135

CONTENTS

Summary

Chapter 1 Background of the Safe System

1.1 Safe System Principles

1.2 Organizational Principles

1.3 Safe System Strategies and Practices

Chapter 2 Safe System Policy

2.1 Key Policy-Related Strategies

2.2 Study-Identified Policy Practices

Chapter 3 Safe System Planning

3.1 Key Planning Strategies

3.2 Study-Identified Planning Practices

Chapter 4 Safe System Design

4.1 Key Design Strategies

4.2 Study-Identified Design Practices

Chapter 5 Safe System Operations and Maintenance

5.1 Key Operations and Maintenance Strategies

5.2 Study-Identified Operations and Maintenance Practices

Chapter 6 Safe System Law Enforcement

6.1 Key Law Enforcement Strategies

6.2 Study-Identified Law Enforcement Practices

Chapter 7 Safe System Post-Crash Response

7.1 Key Post-Crash Response Strategies

7.2 Study-Identified Post-Crash Response Practices

Acronyms and Abbreviations

References

Appendix A Safe System Policy Practices

Appendix B Safe System Planning Practices

Appendix C Safe System Design Practices

Appendix D Safe System Operations and Maintenance Practices

Appendix E Safe System Law Enforcement Practices

Appendix F Safe System Post-Crash Response Practices

Appendix G Safe System Strategy Implementation Self-Assessment