Accessibility Measurement in Transportation Networks and Application to the Seoul Bus System: Accessibility in Transportation Networks

This study presents an algorithm for measuring the time-distance accessibility based on the flow data of actual transportation networks and examines resulting accessibility distributions. Specifically, we construct an extended graph of the transportation network to take into account not only the average speed and transfer time extracted from the data set but also various possible trajectories taken via transfers. Employing the modified Floyd algorithm which finds the shortest time distance, we compute the time-distance accessibility of every bus stop in the Seoul bus system, which yields distinctive skew distributions. We then introduce a time-distance cutoff to focus on effective connections and probe the emergent spatial distributions as the cutoff is varied. Revealed are the characteristic scales as well as spatial structures of the system. It is suggested that the time-distance accessibility can serve as a significant measure to describe and predict the urban land use pattern.