Examining Day-to-Day Dynamic Transit Accessibility Using Functional Data Analysis

Measurements of transit accessibility have been used to evaluate the interactions between transit networks and land use and, more recently, to identify marginalized neighborhoods in need of transportation services to support urban policymaking, transportation planning, and the evaluation of transit systems. Because transit systems are dynamic and their weekly use patterns have high temporal variation, their accessibility is also highly variable across days. In this study, we propose a set of dynamic transit accessibility measures that examine the temporal fluctuations of accessibility by public transit modes. To this end, we employ a novel approach of the functional data analysis that takes cross-area time-dependent curves fitted from the daily accessibility values. We examine Seoul’s intermodal integrated transit system to measure dynamic transit accessibilities to capture the heterogeneity of day-to-day fluctuations in accessibility over the course of a week across neighborhoods. The spatial representation of the dynamic transit accessibilities and the clusters based on the measures reveal an urban structure on which neighborhoods are differentiated by temporal fluctuations of accessibility, not just by a traditional concentric urban pattern of accessibility.