This paper presents the results of a design process for new integrated land use and transportation models recently completed for the Puget Sound Regional Council (PSRC). The design process began with an analysis of policy requirements and assessment of the current models in use at the PSRC and nationally, and used an iterative and participatory approach to ensure that model requirements were clearly identified and that the proposed model design would address these requirements. The development of the model requirements drew on a broad survey of the literature and of operational models, and the proposed model design offers a unique approach to the development of a new land use and travel model system that corresponds to a behavioral integration of the choice processes across relevant time frames.

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Washington State requires large employers in its nine most populous counties to encourage their employees to reduce commuting vehicle trips and to monitor progress by surveying employees. The monitoring requirement yields roughly 250,000 surveys every 2 years. Analysis of the survey results for 1999 and previous years estimated that the program removed an average of 18,500 vehicles from the road during the morning peak in 1999, with 12,600 of these in the Seattle metropolitan area. Information from the surveys was used to construct an origin-destination table for these trips, and the table was then used in a four-step modeling process to estimate the corridors and links that realized the greatest effect of the trip-reduction program. The modeling compared a baseline, which assumed effects of the trip-reduction program, with a case in which trips removed were added back into the trip tables. Results indicate that the trip-reduction program has measurable effects on traffic volumes and delay, both areawide and in specific corridors. The analysis is unique in having these types of data on which to draw for a metropolitan area whose modeling system can use them.

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