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Suggested Citation:"T56712 Text_09." National Academies of Sciences, Engineering, and Medicine. 2008. Innovations in Travel Demand Modeling, Volume 1: Session Summaries. Washington, DC: The National Academies Press. doi: 10.17226/13676.
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9PLENARY SESSION Moving Innovative Models into Practice Martin Wachs, RAND Corporation Keith Lawton, Keith Lawton Consulting Edward Granzow, CH2M Hill Brian Gardner, Federal Highway Administration TRAVEL DEMAND FORECASTING MODELS: RAISING SOME ISSUES Martin Wachs A lot has been accomplished since the previous Travel Model Improvement Program (TMIP) conference on travel demand modeling. There is still a great deal to be done, however, to advance the state of the practice in travel demand forecasting. The TRB study, Determination of the State of the Prac- tice in Travel Forecasting, mentioned by previous speakers is under way and the report should be available in 2007.* I have the privilege of chairing the study committee. The study identified areas in which progress has been made in the application of more advanced travel forecasting mod- els, as well as areas in which little headway has been made. It is important to acknowledge that there is a consensus that there is a need for improvement in travel demand modeling. There is also a feeling that progress is being made at many metropolitan planning organizations (MPOs). The study results also give rise to some concerns. The findings are still preliminary at this point. The TRB Committee on State of the Practice con- ducted a web- based survey of MPOs and states. A total of 228 responses were received from MPOs. The survey results are available on line at www.trb.org/ITPC/ Page01.asp. In addition, in- depth follow- up interviews were conducted with personnel at 13 more innovative MPOs. A total of six interviews were conducted in per- son and the others were completed by telephone. The survey was conducted in detail by Frank Spielberg and members of the committee. Frank deserves a lot of credit for his work. The committee discussion of the survey has been completed and the draft of the final report is in progress. The comments in this presentation are my own, but they are influenced by the survey results and the work of the committee. In 1993, Greg Harvey and Betty Deakin wrote that the state of the practice was not up to the tasks that were being asked of forecasters. At that time, we were begin- ning to discuss issues related to the growing importance of goods movement and pricing. There have been changes since 1993, including greater use of geographic information systems, improved algorithms, more feed- back loops, and increases in the number of zones used in most study areas. The basic model strategies have not improved, however, and these models are being asked to address even more complex tasks. Data inputs remain a problem in most areas. Many jurisdictions reported in the survey that population and economic activity forecasts are negotiated in political processes. Many areas use simple allocation processes to divide forecasts from larger jurisdictions, which is a highly inadequate method of forecasting. Small survey sample sizes and outdated data are common problems in many areas. Given this situation, it might be wiser to allocate limited resources to improve data than to imple- ment advanced models. * Special Report 288, Metropolitan Travel Forecasting: Current Practice and Future Direction, was published by the Transportation Research Board of the National Academies, Washington, D.C., in October 2007 and is available at http://onlinepubs.trb.org/ onlinepubs/sr/sr288.pdf.

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TRB Conference Proceedings 42, Innovations in Travel Demand Modeling, Volume 1: Session Summaries summarizes the sessions of a May 21-23, 2006, conference that examined advances in travel demand modeling, explored the opportunities and the challenges associated with the implementation of advanced travel models, and reviewed the skills and training necessary to apply new modeling techniques.

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