Census Data Field Guide for Transportation Applications (2025)
Chapter: Front Matter
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
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
Bryan Bedford, Administrator, Federal Aviation Administration, Washington, DC
Michael R. Berube, Deputy Assistant Secretary for Sustainable Transportation, U.S. Department of Energy, Washington, DC
Tariq Bokhari, Acting Administrator, Federal Transit Administration, Washington, DC
Steven G. Bradbury, Deputy Secretary, U.S. Department of Transportation, Washington, DC
Steven Cliff, Executive Officer, California Air Resources Board, Sacramento
Drew Feeley, Acting Administrator, Federal Railroad Administration, Washington, DC
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
Niloo Parvinashtiani, Engineer, Mobility Consultant Solutions, Iteris Inc., Fairfax, VA, and Chair, TRB Young Members Coordinating Council
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
Sang Yi, Acting Administrator, U.S. Maritime Administration, Washington, DC
__________________
* Membership as of August 2025.
NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM
NCHRP RESEARCH REPORT 1108
Census Data Field Guide for Transportation Applications
Cambridge Systematics, Inc.
Tallahassee, FL
University of Central Florida
Orlando, FL
Birdʼs Hill Research
Needham, MA
Ed Christopher
Berwyn, IL
Subscriber Categories
Data and Information Technology • Planning and Forecasting • Safety and Human Factors
Research sponsored by the American Association of State Highway and Transportation Officials in cooperation with the Federal Highway Administration
2025
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 1108
Project 08-123
ISSN 2572-3766 (Print)
ISSN 2572-3774 (Online)
ISBN 978-0-309-73399-1
Library of Congress Control Number 2025930875
© 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 manufacturersʼ names or logos appear herein solely because they are considered essential to the object of the report.
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NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM
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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.
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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 Boardʼs 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 1108
Monique R. Evans, Director, Cooperative Research Programs
Waseem Dekelbab, Deputy Director, Cooperative Research Programs, and Manager, National Cooperative Highway Research Program
Christopher T. McKenney, Senior Program Officer
Sheila A. Moore, Program Associate
Natalie Barnes, Director of Publications
Ellen M. Chafee, Senior Editor
NCHRP PROJECT 08-123 PANEL
Field of Transportation Planning—Area of Planning Methods and Processes
Guy Rousseau, Atlanta Regional Commission, Atlanta, GA (Chair)
Ken Chambers, Nevada Department of Transportation, Carson City, NV
Thomas W. Hill, Florida Department of Transportation, Tallahassee, FL
Habte Kassa, Georgia Department of Transportation, Atlanta, GA
Kimberly L. Korejko, Delaware Valley Regional Planning Commission, Philadelphia, PA
Catherine T. Lawson, SUNY Albany, Albany, NY
James T. Meyer, Arizona Department of Transportation, Phoenix, AZ
Quinn N. Molloy, Massachusetts Department of Transportation, Boston, MA
William Morgan, Illinois Department of Transportation, Springfield, IL
Joseph Jay Hausman, FHWA Liaison
Penelope Z. Weinberger, AASHTO Liaison
FOREWORD
By Christopher T. McKenney
Staff Officer
Transportation Research Board
NCHRP Research Report 1108: Census Data Field Guide for Transportation Applications presents a comprehensive field guide for transportation practitioners on how to effectively utilize census data to support transportation analyses. The field guide is based on scenarios that illustrate various uses of census data to address transportation issues. This field guide will be of immediate interest to transportation planners, metropolitan planning organizations (MPOs), and transit operators.
The Census Transportation Planning Products (CTPP) datasets and the American Community Survey (ACS) are critical data elements that support the analysis of transportation plans, policies, programs, and project selection. Changes in the data products over the last 10 years and ongoing staff turnover have left a void of expertise in effectively using these data to support transportation planning. Additionally, there is no centralized resource location where one can go to learn how to use the data for real world applications. This results in wasted time and questionable analysis.
When the ACS was introduced by the Census Bureau as the replacement to the long form, it brought with it a change in how the data were collected and packaged for public release. This, in turn, introduced a whole new set of data issues for transportation analysts. Margins of error, privacy protection rules and procedures, imputation, rounding, data suppression, changes to the survey instrument and variables, and period estimates all have stretched the learning curve for the user of census data. Staff from the states, MPOs, and transit operators have struggled with the use and application of the ACS and data products derived from it like the CTPP and Public Use Microdata Sample/Public Use Microdata Area (PUMS/PUMA).The need to improve road safety performance for all users is important for state departments of transportation and other transportation agencies. At the same time, the optimization of investments by these agencies to save lives and reduce injuries takes on even greater importance when financial resources are constrained. The use of sensors, available data, software applications, and innovative safety performance analyses can help agencies achieve safer roads for all users through targeted investments.
Under NCHRP Project 08-123, “Census Transportation Data Field Guide for Transportation Applications,” Cambridge Systematics was asked to develop a field guide for the transportation community on how to best use census data, including the ACS, CTPP, Longitudinal Employer-Household Dynamics program, and PUMS/PUMA, to address transportation issues. A spreadsheet and multiple files developed by the research team to support use of the field guide can be found on the National Academies Press website (nap.nationalacademies.org) by searching for NCHRP Research Report 1108: Census Data Field Guide for Transportation Applications and then navigating to “Resources.”
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CONTENTS
1.2 History of Transportation in the Census
Chapter 2 American Community Survey
2.1 How ACS Data Are Collected
2.3 Understanding and Using ACS Single-Year and Multiyear Estimates
2.4 Understanding Error and Determining Statistical Significance
Chapter 3 AASHTO Census Transportation Solutions
3.1 History of the CTPP Program
3.2 The Disclosure Review Board
3.4 CTPP Workplace Allocation Issues
Chapter 4 Public Use Microdata Sample
Chapter 5 Longitudinal Employer-Household Dynamics
Chapter 6 National Household Travel Survey and American Time Use Survey
Chapter 7 Differential Privacy
7.1 Issues with Differential Privacy
7.2 Implications of Differential Privacy for Transportation Modelers and Planners
Chapter 11 Field Guide Organization
Chapter 12 Scenario: Travel Survey Weighting
Chapter 13 Scenario: Understanding the Crucial-to-Identify Gaps in Transit
Chapter 14 Scenario: Understanding Nationwide Demographic Trends
Chapter 15 Scenario: Statewide Snapshot of Mean Travel Times
Chapter 16 Scenario: Data Preparation for Travel Demand Model Validation
Chapter 17 Scenario: County Level Employment (Number of Jobs) in the United States
Chapter 19 Resources and Guidelines for Practitioners
19.1 Comparison of Statistical Calculators
19.2 Approximating Standard Errors (and MOEs) for Multiple Estimates
