Understanding Urban Travel Demand: Problems, Solutions, and the Role of Forecasting
Gary Barnes, Gary A Davis
Report no. CTS 99-02
This report is a general examination and critique of transportation policy making, focusing on the role of traffic and land use forecasting. There are four major components: 1. Current, historical, and projected travel behavior in the Twin Cities. 2. The standard travel forecasting model, and some of its shortcomings. 3. The potential application of integrated land use and transportation models. 4. Specific transportation problems and proposed policies in the Twin Cities. The most important result is that the standard traffic forecasting model in its current form is not well suited for evaluating many of the policies of greatest current interest, in particular, those that seek to reduce the overall amount of travel through changes in land use or travel behavior. This model was developed to predict road capacity needs, taking the quantity of travel as more or less uninfluenced by policy. However, currently available improvements, including integrated transportation and land use models, often add little value because they are not based on a well-established theoretical and empirical understanding of travel behavior. The most urgent need in forecasting is not for more complex models, but for a better understanding of the real world processes that the models are attempting to capture.