Incorporating Uncertainty into Long-Range Transportation Planning: A Guide (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 1168
Incorporating Uncertainty into Long-Range Transportation Planning
A GUIDE
Naomi Stein
Allison Van Twisk
Hajra Shahab
Kyle Schroeckenthaler
Adam Schmidt
Daniel Mascoop
EBP US, Inc.
Boston, MA
Peter Hylton
Bryce Miller
Alice Beattie
High Street Consulting Group
Pittsburgh, PA
Adiele Nwankwo
Cincar Consulting (C2G)
Atlanta, GA
Colleen Turner
Michael Baker International
Baltimore, MD
Larry Redd
Redd Engineering
Fort Collins, CO
Subscriber Categories
Administration and Management • Planning and Forecasting • Policy
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 1168
Project 08-154
ISSN 2572-3766 (Print)
ISSN 2572-3774 (Online)
ISBN 978-0-309-60313-3
Library of Congress Control Number 2026934400
© 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.
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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 Board’s 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 1168
Monique R. Evans, Director, Cooperative Research Programs
Waseem Dekelbab, Deputy Director, Cooperative Research Programs, and Manager, National Cooperative Highway Research Program
Trey Joseph Wadsworth, Senior Program Officer
Tijhuana Stapleton, Senior Program Assistant
Natalie Barnes, Director of Publications
Brian Haefs, Associate Director of Publications
Alison Shapiro, Editor
NCHRP PROJECT 08-154 PANEL
Field of Transportation Planning—Area of Planning Methods and Processes
Jennifer Z. Carver, Florida Department of Transportation, Tallahassee, FL (Chair)
Elizabeth G. D. Alden, Tampa, FL
Baloka Belezamo, Arizona Department of Transportation, Phoenix, AZ
Ryan Granger, HNTB, Austin, TX
Benjamin Neal Williams Muller, Massachusetts Department of Transportation, Boston, MA
Bradley M. Sharlow, Michigan Department of Transportation, Lansing, MI
John Spruijt Sr., XTNT, Rijswijk, the Netherlands
Flavia Tsang, Metropolitan Transportation Commission, San Francisco, CA
Carole Turley Voulgaris, Harvard University, Cambridge, MA
Chandra Inglis-Smith, FHWA Liaison
John Dean, AASHTO Liaison
FOREWORD
By Trey Joseph Wadsworth
Staff Officer
Transportation Research Board
NCHRP Research Report 1168: Incorporating Uncertainty into Long-Range Transportation Planning: A Guide presents strategies to assist state departments of transportation (DOTs) with incorporating uncertainty into their long-range transportation planning processes. The guide provides suggestions on plan scoping, development, implementation, and capacity building. It was developed based on an extensive review of literature and practice and documents sources of uncertainty, decision-making frameworks, data and methods, and the regulatory context. The information contained in the guide will be of immediate interest to transportation planners and decision-makers. The findings will serve as a valuable resource for state DOTs and other public transportation agencies.
For decades, state DOTs and metropolitan planning organizations (MPOs) have developed long-range transportation and capital investment plans as required by federal law to ensure the plans meet future and forecasted needs. These plans have anticipated trends and considered uncertainty, however, state DOTs and MPOs are facing new and compounding uncertainties that are difficult to consider, forecast, or fully understand. These challenges, coupled with additional regulatory requirements, have resulted in transportation planning and programming becoming more complex inside more constrained processes. With limited tools at their disposal to help understand uncertainty, including how to utilize methods such as scenario planning, robust decision-making, and risk analysis tools, research was needed to identify points in processes where flexibility exists and how state DOTs and MPOs can better consider uncertainty.
Under NCHRP Project 08-154, “Guidance for Agencies to Incorporate Uncertainty into Long-Range Transportation Planning,” EBP US, Inc. was asked to develop a guide that identifies how, when, where, and why uncertainty should be considered in state DOT and MPO planning and programming processes, with strategies to adapt plans and communicate with stakeholders and decision-makers. The research included a literature review and scan of practice, outreach to the community of practice, case example development, and a peer exchange.
In addition to the guide published as NCHRP Research Report 1168, the following materials are available on the National Academies Press website (nationalacademies.org/publications) by searching for NCHRP Research Report 1168: Incorporating Uncertainty into Long-Range Transportation Planning: A Guide.
- A summary handout.
- An implementation memo.
- A summary presentation.
- A self-evaluation worksheet.
NCHRP Web-Only Document 440, which documents the development of the guide and entire research effort, accompanies this publication and can be found by searching the National Academies Press website (nationalacademies.org/publications) for NCHRP Web-Only Document 440: Developing a Guide for Incorporating Uncertainty into Long-Range Transportation Planning.
CONTENTS
Chapter 1 Introduction: How and Why to Use This Guide
1.3 Success Factors for Managing Uncertainty
2.2 Guided Self-Evaluation and Reflection: Sources of Uncertainty
2.3 Regulatory Context and Requirements
Chapter 3 Long-Range Plan Development
3.2 Forecasting and Needs Estimation
3.3 Methods for Analyzing Uncertainty
4.1 Prioritization to Account for Uncertainty
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