Transit Ridership Evaluation Using Aggregate-Level Causal Analyses of Subway Mode Shares in Seoul, South Korea

Adequate evaluations of transit system efficiency in direct connection with environmental concerns and the economic aspects of the city are critical for development of a better system. This paper presents an evaluation framework by comparing the subway mode shares of 25 districts in Seoul, South Korea. In this effort, causal relationships between the inherent conditions of the district and the resultant mode shares were identified on the basis of regression models with independent variables indicating the system supply level. The expected mode shares from the regression model and the actual shares were then compared as a way to identify districts displaying relatively higher or lower subway mode shares. These processes revealed key influential factors affecting subway mode share and suggest that the system supply level is strongly related to mode share and that ridership increases may be achieved by providing convenient access to stations. The implications of this study are expected to shed light on potential policy actions to improve transit ridership, particularly for those districts with relatively lower levels of ridership.