Transit Route Design Applications Using Geographic Information Systems

Abstract

The design of public transportation networks is made difficult by a multitude of conflicting objectives. For example, networks designed to minimize travel time cannot be expected to maximize coverage and accessibility. Two simple methods for designing and improving public transportation routes with the aid of TransCAD, a geographic information system, are presented. The first method involves a direct demand model that uses readily available socioeconomic and demographic variables to compute a generalized impedance function, which subsequently is used to determine the best alignment for transit routes. The second uses rider origin and destination data (addresses) and TransCAD's address-matching capabilities to improve transit coverage to specific heavy-traffic locations such as universities and hospitals. The first method is illustrated using data from Logan, Utah—a newly urbanized community with a population of approximately 33,000 people and home to Utah State University, which, beginning in 1994, has had an annual enrollment of more than 16,000 students. Two alignments were determined for the same origin-destination pair. The first alignment represents the route established with the sole criterion of minimizing travel distance, and the second represents the route established with the criterion of minimizing the generalized impedance function. When the alignments are compared, the second is found to increase route coverage significantly, but at the expense of a slight increase in travel time.