Twenty years ago the transportation profession was concerned about the quality of traffic forecasting data that are used as a basis for multi-million dollar investment decisions. As a result, a major research study was conducted by NCHRP entitled “Highway Traffic Data for Urbanized Area Project Planning and Design” (NCHRP Report 255). This paper, by an author of the original NCHRP Report, provides a review of lessons learned in the pursuit of the perfect traffic forecast. It revisits many of the key issues associated with trying to produce effective forecasts for both highway and transit planning. Among the topics that the paper addresses include the level of detail inherent in computer travel forecasts, the limitations of quality land-use forecasts, pitfalls in using forecasts for corridor and small-area planning, the wide variation in data available for model validation, and the lack of attention to post-processing of travel forecast output data. (Author/publisher) For the covering entry of this conference, please see ITRD abstract no. E213531.
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