Accessibility Analysis of East Asian Metro Systems

Abstract

Accessibility reflects the ease with which different individuals can overcome travel impedance to reach spatially distributed opportunities. Since accessibility of public transport networks is jointly determined by network topology and service attributes, this study applies access graphs derived from time-weighted L-space and frequency-weighted P-space graphs as the standardized framework. For previously underresearched East Asia region, a new dataset is compiled from open-source data for 61 systems and access graphs are constructed over increasing generalized travel-time budgets, and reachability and equity indicators at critical time points are benchmarked against systems in other world regions. Finally, based on the temporal evolution of average degree, East Asian and metro networks worldwide are classified into four clusters using k-means clustering. The findings show that East Asian metro systems vary widely in sizes. Influenced by the accessibility growth pattern, most medium- to mega-sized networks follow logistic (S-shaped) curves of degree growth consistent with a core–branch structure, whereas smaller or systems with degraded service have irregular degree growth curves. In terms of performance, large systems show greater spatial disparity and less uniform service quality, resulting in lower equity and reachability at 30 minutes. Regardless of size, East Asian metros tend to underperform in the medium and late stages of accessibility growth due to early decay in degree-growth rate and limited reachability at time of maximum degree growth rate. When controlling for size, East Asian metros remain less reachable than European systems and experience earlier growth-rate decay than both European and North American counterparts. Based on the timing of the peak and subsequent decay in degree growth rate, four distinctive accessibility growth patterns are identified across the worldwide systems. Clustering analysis further reveals that large East Asian networks experience an earlier decline in accessibility growth, similar to networks lacking direct cross-line connections, whereas most medium and small networks sustain growth longer on par with those in other regions. The presence of networks of similar size in different clusters suggests that improving service attributes can enhance overall accessibility performance.