Measuring dynamic accessibility by metro system under travel time uncertainty based on smart card data

Measuring dynamic accessibility in the metro system is important for improving operations and for allowing passengers to plan their trips in advance under different circumstances. Yet, due to the large amount of data required, most accessibility studies do not consider the impacts of travel time uncertainty and individual preferences. In metro systems, smart cards record accurate travel information of each passenger. Based on detailed smart card data, this study proposes a framework for measuring dynamic accessibility by the metro system under travel time uncertainty and individual differences. First, dynamic reliable space-time prisms, which consider the impacts of travel time budget, time-varied travel time uncertainty and dynamic individual risk attitude, are used to generate dynamic feasible destination sets. Then, a dynamic destination choice model is built based on the discrete choice model considering the dynamic attractiveness of metro stations and time-varied travel time uncertainty. Finally, this study integrates the two sub-models to measure dynamic accessibility. The dynamic accessibility measure provides a more comprehensive framework for understanding travel behavior by capturing both objective spatial-temporal constraints and individual differences in the dynamic metro environment. The methodology is calibrated and evaluated in the Guangzhou Metro system, where the smart card data is available. The results show that accessibility differs significantly over different time periods. Notably, passengers at late hours are more risk averse to travel time uncertainty. Without considering the dynamic travel time, accessibility will be over-estimated during peak hours on urban lines and during non-peak hours on suburban lines. Moreover, variations of dynamic accessibility of terminal stations in suburban lines are higher.