Factors influencing bus-to-subway transfer duration at subway stations: Evidence from large-scale smart card data in Seoul

In numerous contemporary megacities and their peripheries, subways play an indispensable role within the public transportation system. These cities have established transit networks that revolve around each subway station by means of bus connections. To ensure the subway system's effectiveness, it is imperative for passengers to transfer seamlessly from buses without significant delays. This study utilized large-scale data collected from smart card tags, as well as other infrastructural statistics both within and in proximity to subway stations. We employed accelerated failure time-based multilevel duration modeling techniques to quantitatively examine the correlation between the built environment and transfer duration. Our analysis revealed that proximity to bus stations and access to a greater number of connectable bus routes were associated with reduced transfer durations, underscoring the significance of frequent and well-connected intermodal hubs around subway stations to facilitate rapid transfers. Furthermore, subway stations constructed underground tended to increase transfer durations due to the extended vertical and horizontal distances from adjacent bus stops. Additionally, a positive correlation was observed between roadway density and transfer duration, suggesting pedestrian congestion stemming from significant bus disembarkation on wider roads or delays on densely populated but narrow roadways. These findings offer valuable insights for the design and construction of subway stations, with the goal of providing swift access for passengers transferring from buses. This study contributes to the overall enhancement of the efficiency and serviceability of metropolitan transit systems. • Smart card data shows hierarchical structure, linking multiple bus stops to subway stations. • Having 10+ connectable bus routes reduced bus-to-subway transfer times by 2.7%. • Higher roadway density correlates with longer transfer durations due to pedestrian congestion. • Elevated stations are 12.3% quicker to access than underground ones.