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TRANSPORTAT ION RESEARCH BOARD WASHINGTON, D.C. 2007 www.TRB.org N A T I O N A L C O O P E R A T I V E H I G H W A Y R E S E A R C H P R O G R A M NCHRP REPORT 588 Subject Areas Planning and Administration â¢ Operations and Safety â¢ Aviation â¢ Public Transit Rail â¢ Freight Transportation â¢ Marine Transportation A Guidebook for Using American Community Survey Data for Transportation Planning Cambridge Systematics, Inc. Cambridge, MA NuStats Austin, TX Nancy McGuckin Washington, DC Earl Ruiter Franklin, NH 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 research provides the most effective approach to the solution of many problems facing highway administrators and engineers. Often, highway problems are of local interest and can best be studied by highway departments individually or in cooperation with their state universities and others. However, the accelerating growth of highway transportation develops increasingly complex problems of wide interest to highway authorities. These problems are best studied through a coordinated program of cooperative research. In recognition of these needs, the highway administrators of the American Association of State Highway and Transportation Officials initiated in 1962 an objective national highway research program employing modern scientific techniques. This program is supported on a continuing basis by funds from participating member states of the Association and it receives the full cooperation and support of the Federal Highway Administration, United States Department of Transportation. The Transportation Research Board of the National Academies was requested by the Association to administer the research program because of the Boardâs recognized objectivity and understanding of modern research practices. The Board is uniquely suited for this purpose as it maintains an extensive committee structure from which authorities on any highway transportation subject may be drawn; it possesses avenues of communications and cooperation with federal, state and local governmental agencies, universities, and industry; its relationship to the National Research Council is an insurance of objectivity; it maintains a full-time research correlation staff of specialists in highway transportation matters to bring the findings of research directly to those who are in a position to use them. The program is developed on the basis of research needs identified by chief administrators of the highway and transportation departments and by committees of AASHTO. Each year, specific areas of research needs to be included in the program are proposed to the National Research Council and the Board by the American Association of State Highway and Transportation Officials. Research projects to fulfill these needs are defined by the Board, and qualified research agencies are selected from those that have submitted proposals. Administration and surveillance of research contracts are the responsibilities of the National Research Council and the Transportation Research Board. The needs for highway research are many, and the National Cooperative Highway Research Program can make significant contributions to the solution of 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. Published reports of the NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM are available from: Transportation Research Board Business Office 500 Fifth Street, NW Washington, DC 20001 and can be ordered through the Internet at: http://www.national-academies.org/trb/bookstore Printed in the United States of America NCHRP REPORT 588 Project 8-48 ISSN 0077-5614 ISBN: 978-0-309-09911-0 Library of Congress Control Number 2007908482 Â© 2007 Transportation Research Board COPYRIGHT PERMISSION 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, FAA, FHWA, FMCSA, FTA, or Transit Development Corporation 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 project that is the subject of this report was a part of the National Cooperative Highway Research Program conducted by the Transportation Research Board with the approval of the Governing Board of the National Research Council. Such approval reflects the Governing Boardâs judgment that the program concerned is of national importance and appropriate with respect to both the purposes and resources of the National Research Council. The members of the technical committee selected to monitor this project and to review this report were chosen for recognized scholarly competence and with due consideration for the balance of disciplines appropriate to the project. The opinions and conclusions expressed or implied are those of the research agency that performed the research, and, while they have been accepted as appropriate by the technical committee, they are not necessarily those of the Transportation Research Board, the National Research Council, the American Association of State Highway and Transportation Officials, or the Federal Highway Administration, U.S. Department of Transportation. Each report is reviewed and accepted for publication by the technical committee according to procedures established and monitored by the Transportation Research Board Executive Committee and the Governing Board of the National Research Council. The Transportation Research Board of the National Academies, the National Research Council, the Federal Highway Administration, the American Association of State Highway and Transportation Officials, and the individual states participating in the National Cooperative Highway Research Program do not endorse products or manufacturers. Trade or manufacturersâ names appear herein solely because they are considered essential to the object of this report.
CRP STAFF FOR NCHRP REPORT 588 Christopher W. Jenks, Director, Cooperative Research Programs Crawford F. Jencks, Deputy Director, Cooperative Research Programs Ronald D. McCready, Senior Program Officer Eileen P. Delaney, Director of Publications NCHRP PROJECT 8-48 PANEL Field of Transportation PlanningâArea of Forecasting Alan E. Pisarski, Falls Church, VA (Chair) Cheryl R. Ball, Missouri DOT Ed J. Christopher, Federal Highway Administration Nathan S. Erlbaum, New York State DOT Kara M. Kockelman, University of TexasâAustin Jonette R. Kreideweis, Minnesota DOT Emily Parkany, Mitretek Systems, Inc., Washington, DC Charles L. Purvis, Metropolitan Transportation CommissionâOakland, CA Robert Sicko, Mirai Associates, Kirkland, WA Alice T. Wiggins-Tolbert, Parsons Brinckerhoff, Los Angeles, CA Elaine R. Murakami, FHWA Liaison David H. Clawson, AASHTO Liaison Lynn Weidman, U.S. Census Bureau Liaison Pheny Weidman, RITA Liaison Kimberly Fisher, TRB Liaison Tom Palmerlee, TRB Liaison C O O P E R A T I V E R E S E A R C H P R O G R A M S
Census data have long played a central role in transportation planning and analyses. In particular, the planning community has made extensive use of the Census Long Form. Begin- ning with this decade, the Census Bureauâs American Community Survey (ACS) will replace the Census Long Form. This practitionerâs guidebook focuses on incorporating ACS data into the transportation planning processes at national, state, metropolitan, and local levels. The guidebook evaluates ACS data and products and demonstrates their uses within a wide range of transportation planning applications. Transportation planners, travel demand fore- casters, and others that conduct population and demographic analyses will find this report of significant use. As these transportation professionals struggle to use the limited local data and changing national data as the basis for transportation plans, the report will provide meth- ods and tools to improve the connection between planning and programming. Transportation planners have relied heavily on the decennial Census âlong formâ data because these data provided detailed demographic characteristics along with journey-to- work data for small units of geography such as census tracts or traffic analysis zones (TAZs). It is the long form that provided data for the Census Transportation Planning Package (CTPP), the mostly widely used database for transportation planning. The U.S. Census Bureau is replacing the long form with a continuous data collection program called the American Community Survey (ACS). The transportation planning community needs to know how to use this new source of data in applications such as long-range planning and forecasting, environmental and project analysis, and descriptive statistics. The ACS differs from the decennial Census in many ways, especially as it represents a change from data col- lected at a single point-in-time (April 1, 2000) to data collected continuously throughout the year and summarized annually for large geographic units. Data for TAZs or tracts will be available based on a moving average of data accumulated over a 5-year period. The ACS provides new opportunities and challenges for assessing transportation trends. Guidance is needed on the application, interpretation, and presentation of these new data for transportation planning practitioners and policymakers. This guidebook identifies the key issues that will face transportation planners as they use ACS data to complete analyses that have historically been performed with the decennial Census Long Form data and out- lines potential new transportation planning analyses that transportation planners may conduct with the ACS. This research effort was conducted by Cambridge Systematics, Inc. along with NuStats, Nancy McGuckin, and Earl Ruiter under NCHRP Project 8-48. F O R E W O R D By Kimberly M. Fisher Staff Officer Transportation Research Board
1 Chapter 1 Introduction 1 1.1 Overview of the American Community Survey 2 1.2 Some Important Implications of ACS for Data Users 3 1.3 Purpose and Organization of this Guidebook 4 1.4 Additional Information Sources for an Introduction to ACS 6 Chapter 2 American Community Survey 6 2.1 ACS Implementation 18 2.2 Additional Information Sources on ACS Implementation 22 Chapter 3 Obtaining ACS Data 22 3.1 ACS Data Products 30 3.2 Additional Information Sources for Obtaining ACS Data 31 Chapter 4 Using ACS Data 31 4.1 Accuracy of ACS Data 37 4.2 Data Accumulation over Time and Geography 44 4.3 Data Disclosure Limitations 48 4.4 Understanding, Working with, and Reporting Sample Data 53 4.5 Comparison of ACS Estimates to Census 65 4.6 Implications of ACS Data Release Frequency 73 Chapter 5 Policy Planning and Other Descriptive Analyses Using ACS Data 73 5.1 Descriptive Analyses 76 5.2 Benefits and Limitations of ACS for Descriptive Analyses 76 5.3 Descriptive Analysis Case Studies 101 5.4 Other Specific Uses of Census Data for Descriptive Analyses 102 Chapter 6 Trend Analyses Using ACS Data 102 6.1 Trend Analysis 104 6.2 Benefits and Limitations of ACS for Trend Analysis 104 6.3 Trend Analysis Case Study 111 6.4 Conclusions from the Case Study 114 6.5 Specific Uses of Census Data for Trend Analyses 117 Chapter 7 Transportation Market Analyses Using ACS Data 117 7.1 Transportation Market Analysis 119 7.2 Benefits and Limitations of ACS for Transportation Market Analysis 119 7.3 Transportation Market Analysis: Environmental Justice Case Study 126 7.4 Conclusions from the Case Study 127 7.5 Specific Uses of Census Data for Market Analyses C O N T E N T S
131 Chapter 8 Survey Development and Analysis Using ACS Data 131 8.1 Survey Development and Analysis 132 8.2 Benefits and Limitations of ACS for Survey Development and Analysis 133 8.3 Case Study 141 Chapter 9 Travel Demand Modeling Analyses Using ACS Data 141 9.1 Travel Demand Modeling 144 9.2 Benefits and Limitations of ACS for Travel Demand Modeling 144 9.3 Travel Demand Modeling Case Studies 149 9.4 Specific Uses of Census Data for Travel Demand Modeling 151 Appendix A Housing and Population Questions from ACS and Census Long Form 162 Appendix B ACS Base Tables 185 Appendix C ACS Data Profiles 207 Appendix D ACS Multiyear Profiles 227 Appendix E ACS Ranking Tables 234 Appendix F ACS Thematic Maps 236 Appendix G ACS Subject Tables 246 Appendix H ACS Selected Population Profiles 253 Appendix I Comparison of ACS and Decennial Census Transportation Planning Estimates 263 Appendix J Seasonality Analyses Using ACS