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