Evaluating the Safety Effects of Automated Traffic Signal Performance Measures (2026)
Chapter: Front Matter
TRANSPORTATION RESEARCH BOARD 2026 EXECUTIVE COMMITTEE*
OFFICERS
Chair: Joel M. Jundt, Secretary of Transportation, South Dakota Department of Transportation, Pierre
Vice Chair: Randell Iwasaki, President and CEO, Iwasaki Consulting Services, Walnut Creek, CA
Executive Director: Victoria Sheehan, Transportation Research Board, Washington, DC
MEMBERS
James F. Albaugh,President and CEO, The Boeing Company (retired), Scottsdale, AZ
Marsha Anderson Bomar,Strategic Transportation Advisor, GHD, Duluth, GA
Douglas C. Ceva,Vice President, Customer Lead Solutions, Prologis, Inc., Jupiter, FL
Nancy Daubenberger,Commissioner of Transportation, Minnesota Department of Transportation, St. Paul
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 and Economics, Cazenovia, NY
Edward Hassinger,Director, Missouri Department of Transportation, Jefferson City
Shante Hastings,Cabinet Secretary, Delaware Department of Transportation, Dover
Carol A. Lewis,Professor, Transportation Studies, Texas Southern University, Houston
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
Leslie S. Richards,Professor of Practice, University of Pennsylvania, Philadelphia
Tracy Larkin Thomason,Director, Nevada Department of Transportation, Carson City
Marc Williams,Executive Director, Texas Department of Transportation, Austin
EX OFFICIO MEMBERS
Derek Barrs,Administrator, Federal Motor Carrier Safety Administration, Washington, DC
Steven G. Bradbury,Deputy Secretary, U.S. Department of Transportation, Washington, DC
Stephen Carmel,Administrator, U.S. Maritime Administration, Washington, DC
Tara Cavalline,Professor, University of North Carolina, Charlotte, and Chair, TRB Technical Activities Council
David Fink,Administrator, Federal Railroad Administration, Washington, DC
Firas Ibrahim,Director, Office of Research, Development, and Technology, Office of the Assistant Secretary for Research and Technology, 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, and Chair, TRB Marine Board
Sean McMaster,Administrator, Federal Highway Administration, Washington, DC
Marcus J. Molinaro,Administrator, Federal Transit Administration, Washington, DC
Jonathan Morrison,Administrator, National Highway Traffic Safety Administration, Washington, DC
Seval Oz,Senior Advisor, Office of the Assistant Secretary for Research and Technology, Washington, DC
Niloo Parvinashtiani,Engineer, Mobility Consultant Solutions, Iteris Inc., Fairfax, VA, and Chair, TRB Young Participants Council
Paul Roberti,Administrator, Pipeline and Hazardous Materials Safety Administration, 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 February 2026.
NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM
NCHRP RESEARCH REPORT 1170
Evaluating the Safety Effects of Automated Traffic Signal Performance Measures
Burak Cesme
James Bonneson
Bastian J. Schroeder
Nemanja Dobrota
Laura Zhao
Shannon Warchol
Kittelson & Associates Inc.
Boston, MA
Christopher Day
Jonathan Wood
Anuj Sharma
Iowa State University
Ames, IA
Tingting Huang
Etalyc
Ames, IA
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
2026
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 TRBʼs 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; TRBʼs 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&Iʼs 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 1170
Project 17-109
ISSN 2572-3766 (Print)
ISSN 2572-3774 (Online)
ISBN 978-0-309-60309-6
Library of Congress Control Number 2026934235
© 2026 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 manufacturersʼ 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
Washington, DC 20001
(800) 624-6242
and can be ordered through the internet by going to
nationalacademies.org/publications
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 four centers 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 Boardʼs varied activities annually engage more than 5,500 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 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 1170
Monique R. Evans,Director, Cooperative Research Programs
Waseem Dekelbab,Deputy Director, Cooperative Research Programs, and Manager, National Cooperative Highway Research Program
Patrick Zelinski,Senior Program Officer
Kevin Padilla,Senior Program Assistant
Natalie Barnes,Director of Publications
Brian Haefs,Associate Director of Publications
Brendan Foht,Senior Editor
NCHRP PROJECT 17-109 PANEL
Field of Traffic—Area of Safety
Mark Don Taylor,Utah Department of Transportation, Salt Lake City, UT (Chair)
Jay Grossman,Valparaiso University, Valparaiso, IN
Khalid Jamil,Texas Department of Transportation, Austin, TX
Venkat Nallamothu,Mead & Hunt, Inc., Columbia, MD
Stacie Phillips,Kimley-Horn and Associates, Inc., Raleigh, NC
Sunil Taori,Virginia Department of Transportation, Fairfax, VA
Di Zhu,Tennessee Department of Transportation, Nashville, TN
Woon Kim,FHWA Liaison
Kelly K. Hardy,AASHTO Liaison
FOREWORD
By Patrick Zelinski
Staff Officer
Transportation Research Board
NCHRP Research Report 1170: Evaluating the Safety Effects of Automated Traffic Signal Performance Measures presents two methods for using crash modification factors (CMFs) to evaluate the safety effects of automated traffic signal performance measures (ATSPMs) based on changes in signal timing or operation. The first method produces an estimate of the change in crash frequency and crash cost associated with implementing an ATSPM-based approach to signal timing and operations within a signal system. The second method uses CMFs to quantify the change in crash frequency and severity associated with a specific ATSPM-based change to signal timing or operation at one or more signalized intersections (e.g., the safety effect of reducing red light running). The methods were developed based on data from arterials and signalized intersections in several states over multiple years. This report will be of interest to state departments of transportation, local transportation agencies, and consultants involved in planning, managing, maintaining, or operating traffic signals utilizing ATSPMs.
ATSPMs offer an alternative approach to traditional signal timing. ATSPMs have been shown to help transportation agencies improve operations at signalized intersections through reduced split failures, arrivals on red, red light running, and delays. The right-of-way time allocated to different modes and movements can significantly impact behavior—drivers willing to take smaller gaps, pedestrians waiting for the walk signal, or bicyclists clearing an intersection. While not a true adaptive solution, ATSPMs allow agencies to make near real-time adjustments based on field data. Research was needed to help transportation agencies quantify the changes in crash frequency and severity resulting from the deployment of ATSPM signal timing and developing CMFs.
Under NCHRP Project 17-109, “Crash Modification Factors for Automated Traffic Signal Performance Measures,” Kittelson & Associates, Inc., was asked to develop CMFs for ATSPM signal timing for all modes and various conflict types and severity. The research included a review and prioritization of ATSPMs having an association with safety, a before-and-after study based on data for six arterial street study sites across three states (two arterial streets from three different states), and a cross-sectional study that examined data from three different states that included 109 intersection legs at 42 signalized intersections where ATSPMs were already in operation.
In addition to NCHRP Research Report 1170, the following materials can be found at nationalacademies.org/publications by searching for NCHRP Research Report 1170:
Evaluating the Safety Effects of Automated Traffic Signal Performance Measures:
- ATSPM Safety Evaluation Tool (Excel spreadsheet), which automates the CMF calculations described in this report.
- A technical brief summarizing the research results.
- NCHRP Web-Only Document 442: Crash Modification Factors for Automated Traffic Signal Performance Measures, which documents the research effort and includes an implementation plan and implementation roadmap.
This page intentionally left blank.
