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11 The purpose of this introduction is to set the context and provide background for the remaining chapters of the Guidebook. This chapter also provides a brief overview of Guidebook contents. The research team worked closely with the project panel to outline the contents and organization of the Guidebook on rural and long-distance parameter transferability. The Guidebook is largely organized around the four steps of the modeling process, long-distance and rural trip purposes, different geographies, model applications, and some combination thereof. Additional background information was provided in the Summary and will not be repeated in ensuing chapters of the Guidebook. 1.1 Background The identification of gaps in available data on long-distance and rural travel parameters resulted from a Statewide Model Peer Exchange sponsored by the National Academy of Sciences (NAS) Transportation Research Board (TRB) and held in Longboat Key, Florida, on Septem- ber 23â24, 2004. The resulting Transportation Research Circular (Cambridge Systematics, Inc., 2005) from the peer exchange identifies rural area trip-making characteristics/parameters as the number one ranked research problem statement while long-distance travel data collection ranked number four. Since that time, a final report has been published for NCHRP Project 08-36B, Task 91, Validation and Sensitivity Considerations for Statewide Models (Cambridge Systemat- ics, Inc., 2010d). This report includes the analysis of 30 different statewide models, documenting parameters such as average trip lengths and auto occupancy rates by trip purpose, including a number of long-distance trip purposes unique to particular statewide models. Elsewhere, on the topic of long-distance travel, a scoping project for a national model (Cambridge Systematics, Inc., 2007) was funded through NCHRP. This scoping project laid the groundwork for subsequent phases of developing a national model focused on long-distance travel. This scoping project was followed by initiation of the American Long-Distance Personal Travel (LDPT) Data and Modeling Program (Oak Ridge National Laboratories, 2010). This new program looks to update the 1995 American Travel Survey (ATS), perhaps on a more regular basis, and begin the process of developing a behaviorally based national passenger demand model with multimodal modeling capabilities. At the same time, FHWA recently started work on developing a synthetic national origin-destination (O/D) matrix. A variety of statistics, such as the number of travelers, person-miles traveled, and total travel receipts, indicate that travel and tourism are growing and are becoming increasingly important to the U.S. economy, notwithstanding the recent economic downturn. However, because the data used have not provided a uniform, standardized measure of long-distance travel, data often lack C h a p t e r 1 Introduction
12 Long-Distance and rural travel transferable parameters for Statewide travel Forecasting Models credibility. Small samples and demographic or economic models do not provide the statistical strength to make judgments about capital investment priorities or to understand travelersâ deci- sions based on various price points. 1.2 Research Approach and Work Plan The audience for NCHRP Project 08-84 consists of travel demand modelers with experience in the development and application of statewide and multistate models. Some of the recommen- dations from this study are also relevant to regional travel demand models, particularly those covering significant rural territory and areas with substantial tourist activity. The study will also be useful to researchers who wish to know more about rural and long-distance travel patterns in the United States. Transportation planners involved in policy decision-making about rural and intercity transportation and development patterns will also appreciate much of the information contained in this Guidebook. NCHRP Project 08-84 has focused in part on readily available data and model parameters on long-distance travel. Although the 1995 ATS represents the largest survey conducted on long- distance travel to date, the most recent national source of long-distance passenger travel behavior is the 2001 National Household Travel Survey (NHTS), which defined long-distance trips as those that are 50 miles or more from home. Rural travel parameters can be derived from the more recent 2009 NHTS. Varying length-based definitions (100 miles, 75 miles, and 50 miles from home) are difficult for respondents to conceptualize, leading to many trips reported as âlong-distanceâ being shorter than typically defined trip lengths for these trips. This report uses statistics at different mileage thresholds. New approaches are described to analyze longer-distance travel. Of particular interest is travel between city (or regional) pairs. Even at the statewide modeling level, data on external and rural travel is poor or nonexistent. The research conducted under this study was dually focused on synthesizing information from various models and an original contribution to transferable parameters. In addition to a synthesis of available models and documents, this Guidebook describes analysis of data from available surveys such as the NHTS and ATS, as well as surveys previously completed by team members and state DOTs, in order to develop original source material on transferable parameters. 1.3 Guidebook Organization Chapter 2 of this Guidebook is focused on providing recommendations on the best stratifica- tions for long-distance and rural trip-making based on statistical analyses for this project as well as coordination with other research efforts such as NCHRP Project 25-36 (Department of City and Regional Planning Center for Urban and Regional Studies University of North Carolina at Chapel Hill, 2011); national household-based surveys of long-distance travel, such as the ATS and NHTS; and statewide and regional travel surveys that address long-distance and rural travel markets. The latter includes statewide DOT surveys and NHTS Add-On surveys sponsored by state DOTs. Chapter 3 of this report provides guidance on when to, versus when not to, transfer param- eters, depending on available data sources and other considerations, expanding on discussions on this topic found in the Summary.
Introduction 13 Chapters 4 through 6 focus on transferable model parameters and benchmarks for each step in the traditional four-step modeling process. Chapter 4 focuses on trip generation, Chapter 5 on trip distributions, and Chapter 6 on auto occupancy and mode choice. The report concludes with Chapter 7, which provides a summary of comparisons and conclusions. As part of a project funded by FHWA, Oak Ridge National Laboratory (ORNL) (Oak Ridge National Laboratory, 2010), with support from University of Maryland (UMD) researchers, completed a comprehensive review of existing multimodal large-scale travel demand models to identify data sources and modeling options for long-distance travel and rural travel, including other national and multinational models. The age, objective, methodology, and data sources of selected long-distance and rural travel models from that review have been summarized in tabular form for reference in Appendix A of this report. Appendix B is a discussion of household surveys from Canada and other countries that include information on rural and long-distance travel. This is followed by a discussion of modal-based information on long-distance travel, including passenger air, intercity bus, and intercity rail as provided in Appendix C. Appendix D is a synopsis of other demographic and O/D survey data, including new technologies used to identify travel patterns without direct interview of travelers. Appendix E focuses on a discussion of freight and nonfreight trucks because commercial traffic must be combined with passenger trips in order to get the full picture on rural and long-distance travel for statewide models. Appendix F provides background information on some of the state- wide models reviewed for this Guidebook. Appendixes G through I are not contained in this report but are available by searching for the report title on the TRB website. Appendix G presents a series of rural typology variables considered in stratifying model parameters and benchmarks and identifies the statistical significance of each. Appendix H contains rural trip production rates for several different cross-classification schemes and the trip rates associated with each. Finally, Appendix I provides additional infor- mation on auto occupancy rates.
