SPECIAL REPORT 288

METROPOLITAN TRAVEL FORECASTING

Current Practice and Future Direction

Committee for Determination of the State of the Practice in Metropolitan Area Travel Forecasting

TRANSPORTATION RESEARCH BOARD OF THE NATIONAL ACADEMIES

Transportation Research Board

Washington, D.C.

2007
www.TRB.org



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SPECIAL REPORT 288 METROPOLITAN TRAVEL FORECASTING Current Practice and Future Direction Committee for Determination of the State of the Practice in Metropolitan Area Travel Forecasting Transportation Research Board Washington, D.C. 2007 www.TRB.org

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Transportation Research Board Special Report 288 Subscriber Category IA planning and administration Transportation Research Board publications are available by ordering individual publica- tions directly from the TRB Business Office, through the Internet at www.TRB.org or national-academies.org/trb, or by annual subscription through organizational or individual affiliation with TRB. Affiliates and library subscribers are eligible for substantial discounts. For further information, contact the Transportation Research Board Business Office, 500 Fifth Street, NW, Washington, DC 20001 (telephone 202-334-3213; fax 202-334-2519; or e-mail TRBsales@nas.edu). Copyright 2007 by the National Academy of Sciences. All rights reserved. Printed in the United States of America. NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competencies and with regard for appropriate balance. This report has been reviewed by a group of individuals other than the authors accord- ing to the procedures approved by a Report Review Committee consisting of members of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. This report was sponsored by the Federal Highway Administration, the Federal Transit Administration, and the Office of the Secretary of Transportation of the U.S. Department of Transportation, and the Transportation Research Board. Cover and design by Tony Olivis, Studio 2. Library of Congress Cataloging-in-Publication Data Metropolitan travel forecasting : current practice and future direction / Committee for Determination of the State of the Practice in Metropolitan Area Travel Forecasting. p. cm.—(Transportation Research Board special report ; 288) 1. Urban transportation—United States—Planning. 2. Traffic estimation—United States. 3. Urban transportation policy—United States. I. National Research Council (U.S.). Committee for Determination of the State of the Practice in Metropolitan Area Travel Forecasting. HE308.M48 2007 388.4011′2—dc22 2007036812 ISBN 978-0-309-10417-3

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The National Academy of Sciences is a private, nonprofit, self-perpetuating society of dis- tinguished scholars engaged in scientific and engineering research, dedicated to the further- ance of science and technology and to their use for the general welfare. On the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Ralph J. Cicerone is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. Charles M. Vest is president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of pol- icy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, on its own initiative, to identify issues of medical care, research, and education. Dr. Harvey V. Fineberg is president of the Institute of Medicine. The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy’s pur- poses of furthering knowledge and advising the federal government. Functioning in accor- dance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the sci- entific and engineering communities. The Council is administered jointly by both the Academies and the Institute of Medicine. Dr. Ralph J. Cicerone and Dr. Charles M. Vest are chair and vice chair, respectively, of the National Research Council. The Transportation Research Board is one of six major divisions of the National Research Council. The mission of the Transportation Research Board is to provide leader- ship in transportation innovation and progress through research and information ex- change, conducted within a setting that is objective, interdisciplinary, and multimodal. The Board’s varied activities annually engage about 7,000 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 transportation departments, federal agencies including the component administra- tions of the U.S. Department of Transportation, and other organizations and individuals interested in the development of transportation. www.TRB.org www.national-academies.org

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Committee for Determination of the State of the Practice in Metropolitan Area Travel Forecasting Martin Wachs, RAND Corporation, Santa Monica, California, Chair Laura L. Cove, Town of Cary, North Carolina Thomas B. Deen, Consultant, Stevensville, Maryland George B. Dresser, Texas Transportation Institute, College Station Ronald W. Eash, Northwestern University, Evanston, Illinois Robert A. Johnston, University of California, Davis Eric J. Miller, University of Toronto, Canada Michael R. Morris, North Central Texas Council of Governments, Dallas Richard H. Pratt, Richard H. Pratt, Consultant, Inc. Charles L. Purvis, Oakland Metropolitan Transportation Commission, California Guy Rousseau, Atlanta Regional Commission, Georgia Mary Lynn Tischer, Virginia Department of Transportation, Richmond Richard E. Walker, Metro Portland, Portland, Oregon Transportation Research Board Staff Jon M. Williams, Study Director

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Preface M etropolitan planning organizations (MPOs) develop regional transportation plans and programs to accommodate mobility needs within their regions. This process is commonly performed with the assistance of computerized travel demand models that provide information on current and future transportation system operations. In 2003, the Transportation Research Board (TRB) of the National Research Council (NRC) conducted a peer review of the travel demand mod- eling of the Metropolitan Washington Council of Governments’ (MWCOG) Transportation Planning Board (TPB), the MPO for Washington, D.C. In the course of this review, it became apparent that little information is available to practitioners to assist them in making judgments about state-of-the-practice techniques for model development and application. Although the NRC com- mittee that conducted the review was charged with assessing whether the mod- eling of the MWCOG TPB was state of the practice, the committee had to rely on its judgment in making this assessment, rather than on detailed infor- mation about how key technical issues are treated by the MPO’s peers. In this context, the Federal Highway Administration (FHWA), the Federal Transit Administration (FTA), and the Office of the Secretary of Transportation (OST) and TRB funded a new TRB study to gather infor- mation needed to determine the national state of practice in metropolitan area travel demand forecasting by MPOs and state departments of trans- portation (DOTs). The statement of task for this study comprised three main elements: (a) description of the current state of practice in metro- politan travel forecasting; (b) evaluation of the current state of practice, including any deficiencies; and (c) recommendations for improvement. This main report responds to each of these elements, although it empha- sizes the latter two. In addition, a companion technical report commis- sioned for this study provides supporting detail on current MPO modeling practice, although the reader should not need to consult that v

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METROPOLITAN TRAVEL FORECASTING Current Practice and Future Direction vi report for a broad understanding of the committee’s findings and recom- mendations. The detailed charge to the committee may be found in the appendix to this report. To conduct this study, TRB formed a committee chaired by Martin Wachs, then director of the Institute of Transportation Studies at the University of California, Berkeley, and currently director of the RAND Corporation’s Transportation, Space, and Technology Program. The 12 committee members brought to the study expertise in four broad areas: the relationship of travel forecasting to public policy and planning, the devel- opment of applied travel forecasting models, the application of travel fore- casting models, and independent academic research on travel forecasting. In addition, committee members were expert in key areas of interest, includ- ing land use planning and modeling, air quality emissions estimates, transit modeling, and data collection and analysis. The committee supplemented its own expertise by seeking technical guidance from three corporations that were responsible for much of the model development in U.S. metropolitan areas: PB Consult, Inc., Cambridge Systematics, Inc., and AECOM. To gather the detailed information on travel modeling practice needed to respond to its charge, the committee employed a consulting firm, BMI- SG, Inc. (subsequently VHB, Inc.). The consultant conducted a web-based survey of modeling practice among all MPOs. Responding to this survey were 60 percent of all MPOs and 84 percent of those with a population exceeding 1 million. The consultant also conducted an extensive literature review, as well as in-depth interviews at 16 MPOs or state DOTs that per- form modeling for MPOs in their state. To be further advised on topics relating to the study, the committee requested and received at its meetings presentations from staff of FHWA, FTA, OST, the U.S. Environmental Protection Agency, the Association of Metropolitan Planning Organizations (AMPO), the American Association of State Highway and Transportation Officials’ (AASHTO’s) Standing Committee on Planning, Environmental Defense, and the TRB Committee on Transportation Planning Applications. Particular topics on which the committee asked to be briefed were FTA’s New Starts program, FHWA’s TRANSIMS modeling initiative, and FHWA’s Freight Models Improve- ment Program. In addition, the committee held a joint meeting with the AMPO Travel Models Working Group to discuss the initial findings of the above web-based survey of MPO modeling practice.

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Preface vii The committee deliberated carefully as to the intended audience for its report. It concluded that the primary audience for this main report, with its findings and recommendations, should be those with a broad interest in metropolitan transportation planning, programming, and policy making, such as MPO policy board members. The committee was well aware that travel forecasting is a complex topic, with specialized concepts and language that may not be accessible to that primary audience. It therefore attempted to ensure that this main report would be largely nontechnical; where tech- nical modeling terms are used, they are explained. This report has been reviewed in draft form by individuals chosen for their diverse perspectives and technical expertise, in accordance with proce- dures approved by NRC’s Report Review Committee. The purpose of this independent review is to provide candid and critical comments that assist the authors and NRC in making the published report as sound as possible and to ensure that the report meets institutional standards for objectivity, evidence, and responsiveness to the study charge. The contents of the review comments and draft manuscript remain confidential to protect the integrity of the deliberative process. The committee thanks the following individuals for their participation in the review of this report: Elizabeth A. Deakin, University of California, Berkeley; Mark E. Hallenbeck, University of Washington, Seattle; Lester A. Hoel, University of Virginia; Charles E. Howard, Jr., Puget Sound Regional Council; Keith L. Killough, Southern California Association of Governments; Ronald F. Kirby, MWCOG; Frank S. Koppelman, Northwestern University; and T. Keith Lawton, Keith Lawton Consulting, Inc. Although the reviewers listed above provided many constructive com- ments and suggestions, they were not asked to endorse the committee’s conclusions or recommendations, nor did they see the final draft of the report before its release. The review of this report was overseen by Adib K. Kanafani, University of California, Berkeley, and C. Michael Walton, University of Texas at Austin. Appointed by NRC, they were responsible for making certain that an independent examination of the report was carried out in accordance with institutional procedures and that all re- view comments were carefully considered. Responsibility for the final content of this report rests entirely with the authoring committee and the institution. Jon M. Williams of TRB managed the study and drafted the final report under the guidance of the committee and the supervision of Stephen R.

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METROPOLITAN TRAVEL FORECASTING Current Practice and Future Direction viii Godwin, Director of Studies and Special Programs at TRB. Suzanne Schneider, Associate Executive Director of TRB, managed the report review process. Frances Holland and Amelia Mathis assisted with meeting arrange- ments and communications with committee members. Rona Briere edited the report, and Alisa Decatur prepared the edited manuscript. From the TRB Publications Office staff, Norman Solomon, Senior Editor; Jennifer J. Weeks, Editorial Services Specialist; and Juanita Green, Production Manager, assisted with the final report publication, under the supervision of Javy Awan, Director of Publications. ACKNOWLEDGMENTS The committee particularly acknowledges the contribution of Frank Spielberg, who, as principal investigator from VHB, led the gathering and interpretation of technical information, attended all committee meetings, and greatly helped the committee in shaping its findings and recommenda- tions, with the assistance of Phillip Shapiro, the VHB co–principal investi- gator. Ramanujan Jagannathan and Srividya Vadlamani made substantial contributions to surveys of MPOs. David Anspacher and Richard Roisman contributed to data analysis and fact checking. Principals from three national consulting firms provided the committee with valuable information on current technical practice. They were William Davidson of PB Consult, Inc., Thomas Rossi of Cambridge Systematics, Inc., and William Woodford of AECOM. The committee supplemented its expertise with briefings at its meet- ings from federal, state, and local government officials and practitioners; public interest groups; and other interested parties. The committee thanks Edward Weiner, OST; Cynthia Burbank, Gloria Shepherd, Rolf Schmitt, Fred Ducca, Bruce Spear, and Brian Gardner, FHWA; Ron Fisher and Eric Pihl, FTA; John Davies, U.S. Environmental Protection Agency; Michelle Pourciau, D.C. Department of Transportation; Ron Milone, MWCOG; Jerry Faris, Chair of the TRB Committee on Transportation Planning Applications; Michael Replogle, Environmental Defense; Jennifer John, Metro Portland; Felix Nwoko, Durham–Chapel Hill–Carrboro MPO; and Mark Wilkes, Metro Planning Commission, Savannah, Georgia.

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Preface ix A number of associations were especially helpful to the committee in its information gathering and deliberations. In particular, the committee thanks the Honorable Rae Rupp Srch, President, DeLania Hardy, Executive Director, and Rich Denbow, Director of Technical Programs, AMPO; the Honorable James L. Kennedy, President, and Peggy Tadej, Director of Research, National Association of Regional Councils; and Debra L. Miller, Chair, AASHTO Standing Committee on Planning.

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Contents SUMMARY FINDINGS AND RECOMMENDATIONS. . . . . . 1 Study Charge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Findings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Overview of Travel Forecasting . . . . . . . . . . . . . . . . . . . . . . . . . 15 Report Organization and Approach . . . . . . . . . . . . . . . . . . . . . . 17 2 FORECASTING METROPOLITAN TRAVEL . . . . . . . . . . . . 19 Historical Context . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 MPO Planning and Travel Demand Forecasting Models. . . . . . 23 Expanded Requirements for Metropolitan Travel Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 Summary Findings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 3 INSTITUTIONAL FRAMEWORK FOR TRAVEL DEMAND MODELING. . . . . . . . . . . . . . . . . . . . . . 35 Federal Government . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 State Transportation Agencies . . . . . . . . . . . . . . . . . . . . . . . . . . 38 Combined Efforts of STAs and MPOs . . . . . . . . . . . . . . . . . . . 39 Summary Findings and Recommendations . . . . . . . . . . . . . . . . 43

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4 CURRENT STATE OF THE PRACTICE . . . . . . . . . . . . . . . . 46 Web-Based Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 MPO Interviews. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 Matching the Model to the Context . . . . . . . . . . . . . . . . . . . . . 59 Summary Findings and Recommendations . . . . . . . . . . . . . . . . 61 5 SHORTCOMINGS OF CURRENT FORECASTING PROCESSES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 Inherent Weaknesses of Current Models . . . . . . . . . . . . . . . . . . 67 Errors Introduced by Modeling Practice . . . . . . . . . . . . . . . . . . 72 Lack or Questionable Reliability of Data . . . . . . . . . . . . . . . . . . 75 Biases Arising from the Institutional Climate. . . . . . . . . . . . . . . 81 Summary Findings and Recommendations . . . . . . . . . . . . . . . . 84 6 ADVANCING THE STATE OF THE PRACTICE . . . . . . . . . 90 Improvements in Four-Step Trip-Based Modeling. . . . . . . . . . . 90 Advanced Modeling Practices. . . . . . . . . . . . . . . . . . . . . . . . . . . 92 TRANSIMS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 Experience with Advanced Practice . . . . . . . . . . . . . . . . . . . . . 100 Obstacles to Model Improvements. . . . . . . . . . . . . . . . . . . . . . 104 Model Research, Development, and Implementation. . . . . . . . 107 Summary Findings and Recommendations . . . . . . . . . . . . . . . 114 7 THE PACE OF CHANGE AND INNOVATION . . . . . . . . . 122 APPENDIX: COMMITTEE STATEMENT OF TASK . . . . . 125 STUDY COMMITTEE BIOGRAPHICAL INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127