JOURNAL OF TRANSPORTATION AND STATISTICS Volume 6 Number 1, 2003 ISSN 1094-8848 BUREAU OF TRANSPORTATION STATISTICS UNITED STATES DEPARTMENT OF TRANSPORTATION Vo JOURNAL OF TRANSPORTATION lume 6 Number 1, 2003 AND STATISTICS Volume 6 Number 1, 2003 ISSN 1094-8848 CONTENTS DONALD C SHOUP [ with discussion by Carl H Buttke and Eugene D Arnold, Jr ] Truth in Transportation Planning HARIKESH S NAIR + CHANDRA R BHAT Modeling Trip Duration for Mobile Source Emissions Forecasting SHAW-PIN MIAOU, JOON JIN SONG + BANI K MALLICK Roadway Traffic Crash Mapping: A Space-Time Modeling Approach BUREAU OF TRANSPORTATION STATISTICS UNITED STATES DEPARTMENT OF TRANSPORTATION SARAH T BOWLING + LISA AULTMAN-HALL Development of a Random Sampling Procedure for Local Road Traffic Count Locations JOURNAL OF TRANSPORTATION PIYUSH TIWARI, HIDEKAZU ITOH + MASAYUKI DOI Containerized AND STATISTICS Cargo Shipper’s Behavior in China: A Discrete Choice Analysis JOURNAL OF TRANSPORTATION AND STATISTICS JOHN V. WELLS Editor-in-Chief PEG YOUNG Associate Editor MARSHA FENN Managing Editor JENNIFER BRADY Assistant to the Editor-in-Chief DORINDA EDMONDSON Desktop Publisher ALPHA GLASS Editorial Assistant LORISA SMITH Desktop Publisher MARTHA COURTNEY Editor DARCY HERMAN Editor EDITORIAL BOARD KENNETH BUTTON George Mason University TIMOTHY COBURN Abilene Christian University STEPHEN FIENBERG Carnegie Mellon University GENEVIEVE GIULIANO University of Southern California JOSE GOMEZ-IBANEZ Harvard University DAVID GREENE Oak Ridge National Laboratory KINGSLEY HAYNES George Mason University DAVID HENSHER University of Sydney PATRICIA HU Oak Ridge National Laboratory RICHARD JOHN Volpe National Transportation Systems Center, USDOT T.R. LAKSHMANAN Boston University TIMOTHY LOMAX Texas Transportation Institute PETER NIJKAMP Free University KEITH ORD Georgetown University ALAN PISARSKI Consultant ROBERT RAESIDE Napier University JEROME SACKS National Institute of Statistical Sciences TERRY SHELTON U.S. Department of Transportation KUMARES SINHA Purdue University ROBERT SKINNER Transportation Research Board CLIFFORD SPIEGELMAN Texas A&M University DARREN TIMOTHY U.S. Department of Transportation PIYUSHIMITA (VONU) THAKURIAH University of Illinois at Chicago MARTIN WACHS University of California at Berkeley C. MICHAEL WALTON The University of Texas at Austin The views presented in the articles in this journal are those of the authors and not necessarily the views of the Bureau of Transportation Statistics. All material contained in this journal is in the public domain and may be used and reprinted without special permission; citation as to source is required. JOURNAL OF TRANSPORTATION AND STATISTICS Volume 6 Number 1, 2003 ISSN 1094-8848 BUREAU OF TRANSPORTATION STATISTICS UNITED STATES DEPARTMENT OF TRANSPORTATION U.S. DEPARTMENT OF The Journal of Transportation and Statistics releases TRANSPORTATION three numbered issues a year and is published by the NORMAN Y. MINETA Bureau of Transportation Statistics Secretary U.S. Department of Transportation Room 7412 BUREAU OF TRANSPORTATION 400 7th Street SW STATISTICS Washington, DC 20590 USA RICK KOWALEWSKI [email protected] Deputy Director WILLIAM J. CHANG Associate Director for Information Systems Subscription information To receive a complimentary subscription JOHN V. WELLS or a BTS Product Catalog: Chief Economist mail Product Orders JEREMY WU Bureau of Transportation Statistics Acting Chief Statistician U.S. Department of Transportation Room 7412 400 7th Street SW Washington, DC 20590 USA phone 202.366.DATA Bureau of Transportation Statistics fax 202.366.3197 internet www.bts.gov Our mission: To lead in developing transportation data and information of high quality and to Information Service advance their effective use in both public and email [email protected] private transportation decisionmaking. phone 800.853.1351 Our vision for the future: Data and information of high quality supporting every significant Cover and text design Susan JZ Hoffmeyer transportation policy decision, thus advancing Cover photo © 2003/Getty Images the quality of life and the economic well-being of all Americans. The Secretary of Transportation has determined that the publication of this periodical is necessary in the transaction of the public business required by law of this Department. ii JOURNAL OF TRANSPORTATION AND STATISTICS Volume 6 Number 1 2003 Contents Papers in This Issue Truth in Transportation Planning Donald C. Shoup . 1 Discussion Carl H. Buttke and Eugene D. Arnold, Jr. 13 Rejoinder Donald C. Shoup . 15 Modeling Trip Duration for Mobile Source Emissions Forecasting Harikesh S. Nair and Chandra R. Bhat . 17 Roadway Traffic Crash Mapping: A Space-Time Modeling Approach Shaw-Pin Miaou, Joon Jin Song, and Bani K. Mallick . 33 Development of a Random Sampling Procedure for Local Road Traffic Count Locations Sarah T. Bowling and Lisa Aultman-Hall . 59 Containerized Cargo Shipper’s Behavior in China: A Discrete Choice Analysis Piyush Tiwari, Hidekazu Itoh, and Masayuki Doi . 71 Guidelines for Manuscript Submission . 87 iii Truth in Transportation Planning DONALD C. SHOUP University of California, Los Angeles ABSTRACT Transportation engineers and urban planners often report uncertain estimates as precise numbers, and unwarranted trust in the accuracy of these precise numbers can lead to bad transportation and land- use policies. This paper presents data on parking and trip generation rates to illustrate the misuse of precise numbers to report statistically insignificant estimates. Beyond the problem of statistical insignif- icance, parking and trip generation rates typically report the parking demand and vehicle trips observed at suburban sites with ample free parking and no public transit. When decisionmakers use these parking and trip generation rates for city plan- ning, they create a city where everyone drives to their destinations and parks free when they get there. Beware of certainty where none exists. DANIEL PATRICK MOYNIHAN INTRODUCTION How far is it from San Diego to San Francisco? An estimate of 632.125 miles is precise but not accu- rate. An estimate of somewhere between 400 and 500 miles is less precise but more accurate, because KEYWORDS: parking, regression analysis, urban planning. 1 the correct answer is 460 miles.1 Nevertheless, if lected at suburban localities with little or no transit service, nearby pedestrian amenities, or you did not know the distance from San Diego to travel demand management programs. San Francisco, whom would you believe: someone ITE says nothing about the price of parking at the who confidently says 632.125 miles or someone study sites, but since parking is free for 99% of who tentatively says somewhere between 400 and vehicle trips in the United States, most of the study 500 miles? You would probably believe the one sites probably offer free parking.2 Trip Generation who says 632.125 miles, because precision creates uses these 3,750 studies to estimate 1,515 trip gen- the impression of accuracy. eration rates, one for each type of land use. Half the Although reporting estimates with extreme preci- 1,515 reported trip generation rates are based on sion suggests confidence in their accuracy, transpor- five or fewer studies, and 23% are based on a single tation engineers and urban planners often use study.3 The trip generation rates thus typically mea- precise numbers to report uncertain estimates. As sure the number of vehicle trips observed at a few examples of this practice, I will use two manuals suburban sites with free parking but little or no pub- published by the Institute of Transportation Engi- lic transit service, pedestrian amenities, or travel neers (ITE): Parking Generation (ITE 1987a) and demand management (TDM) programs. Urban Trip Generation (ITE 1987b, 1991, 1997). These planners who rely on these trip generation rates as manuals have enormous practical consequences for guides to design the transportation system are there- transportation and land use. Urban planners rely on fore planning an automobile-dependent city. parking generation rates to establish off-street park- Figure 1 shows a typical page from the fourth ing requirements, and transportation planners rely edition of Trip Generation (ITE 1987b).4 It reports on trip generation rates to predict the traffic impacts the number of vehicle trips to and from fast food of development proposals. Yet a close look at the restaurants on a weekday. Each point in the figure parking and trip generation data shows that placing represents one of the eight studies and shows the unwarranted trust in these precise but uncertain number of vehicle trips per day and the floor area at estimates of travel behavior leads to bad transporta- a restaurant. Dividing the number of vehicle trips by tion and land-use policies. the floor area at that restaurant gives the trip genera- tion rate at that restaurant. A glance at the figure TRIP GENERATION suggests that vehicle trips are unrelated to floor area 2 Trip Generation reports the number of vehicle in this sample. The extremely low R of 0.069 for trips as a function of land use. Transportation the fitted curve (regression) equation confirms this engineers survey the number of vehicle trips to and 2 from a variety of locations, and for each land use The U.S. Department of Transportation’s 1990 Nation- wide Personal Transportation Survey (NPTS) asked the ITE reports a trip generation rate that relates respondents, “Did you pay for parking during any part of the number of vehicle trips to a characteristic of this trip?” for all automobile trips made on the previous the land use, such as the floor area or number of day. Of the responses to this question, 99% were “no.” The NPTS asked the “did you pay for parking” question employees at a site. The sixth (and most recent) for all vehicle trips except trips that ended at the respon- edition of Trip Generation (ITE 1997, vol. 3, pp. dents’ homes, thus free parking at home does not explain ix and 1) describes the data used to estimate trip this high percentage. 3 generation rates as follows: This refers to the sixth edition of Trip Generation (ITE 1997). The ITE Trip Generation Handbook (ITE 2001, p.