Trafic Forecasting for Small- to Medium-Sized Urban Areas

I nrecent years there has been a noticeable shift away from the application of computer-based transportation modeling methods in smallto medium-sized urban areas. In many cases, this shift has resulted from a disenchantment with the complex modeling methodologies used in the late 1960s and early 1970s. The expense of such methods, in terms of data collection and computational costs, was simply not worth the marginal improvement in forecasting accuracy over “quick-response” methods. Consequently, since the mid-1970s, agencies in smallto medium-sized urban areas have implemented relatively simplistic methods of forecasting traffic flows. Such forecasts have been used as a basis to justify transportation facility improvement projects that often entail hundreds of thousands of dollars of capital investment. Given the important role that traffic impact forecasting can play in the efficient allocation of transportation funds, it is clear that any improvements in “implementable” forecasting techniques could be of considerable value to transportation agencies. Recent efforts to improve implementable forecasting methods’ 2 have, however, achieved only mixed success’. This article describes a recently developed methodological package that can be readily applied to forecast the traffic-related impacts of a wide range of transportation-facility -related improvements. The package uses some of the most advanced transportation analysis techniques to predict traffic flows and measure the performance of specific highway links and the network as a whole. In addition, an attempt is made to keep data requirements to a minimum. Overview of the Methodological Approach