Abstract With the rapid emergence of e-payment methods, such as WeChat and Alipay, in China, more passengers choose mobile payment instead of traditional methods such as ticket counters at the station or travel cards when taking public rail transit systems. However, the mechanisms and key drivers of passengers' payment choices when purchasing tickets with new e-payment ticketing channels are significantly underdeveloped. In this paper, a combination of field and online surveys on the city metro system and its passengers was conducted in Xi'an, China, to collect socioeconomic characteristics, residence locations, travel frequency, mobile phone usage information, and payment choices. The Random Forest (RF) model and SHapley Additive exPlanations (SHAP) were used to explore the relationship between payment choices and those passenger-related attributes. The results reveal that travel card ownership, occupation, residence location, travel purpose, education level, and gender are important and influential factors that can effectively affect passengers' preferences regarding how they would like to pay. Subsequent discussions and implications concerning e-payment ticketing channels in rail transit systems were also put forward. This study offers new insights and evidence for a better understanding of the underlying mechanism of passengers' ticketing choice behaviors in this increasingly digitalized era.

Highlights • A thorough investigation of the mechanisms and key drivers of rail transit passengers' payment choices. • Heterogeneity can be found in passengers' payment choices. • Travel card ownership has the greatest influence on passengers' payment choices. • Implications are proposed for guiding future data-driven decision and policy-making.