Transportation Activity Centers for Urban Transportation Analysis

Abstract

North American cities have been evolving from monocentric to polycentric metropolitan regions, with multiple concentrations of activities occurring outside of traditional urban cores. This new urban structure, with multiple urban “activity centers,” has profound influence on the functioning of cities, particularly transportation systems. This paper reviews the development of “activity center” definitions from various research fields, and concludes that the application of contemporary definitions to transportation analyses has significant weaknesses, particularly in analyzing suburban agglomerations of activities. An alternative method is suggested which incorporates not only the presence of concentrated employment, the traditional criteria, but also the trip-attracting strength of the employment types present in an activity center. The Philadelphia metropolitan area is analyzed using traditional definitions and the proposed methodology; several areas which would not be identified using traditional definitions meet the new criteria. The impact of these “transportation activity centers” on Philadelphia’s travel patterns is explored.