Exploring non-linear built environment effects on the integration of free-floating bike-share and urban rail transport: A quantile regression approach

Bike-sharing offers a convenient feeder mode for connecting to public transport, which helps to address the last-mile problem. However, few studies have examined the nuanced relationship between the built environment and the integration of free-floating bike-sharing (FFBS) with urban rail transport (URT). Drawing on weekly records of 3.12 million trips of the FFBS system in Nanjing, China, we examined the nonlinear effects of the built environment on FFBS-URT integrated use. A quantile regression method is utilised to estimate the relationships for morning and evening peaks, respectively. The results demonstrate the existence of the nonlinearity of the relationships. The effects of the built environment show variations in the significance levels and magnitudes of coefficients, depending on the quantiles. For example, the length of minor roads in station areas is strongly related to the integrated use at low quantile stations, whereas this effect is not statistically significant at medium and high quantiles. We also find that bicycle infrastructure displays more salient nonlinear effects than land-use variables and external transport facilities. In addition, temporal differences in the relationships between the built environment and the integrated use are also unveiled. Our findings help to inform dedicated and effective built environment interventions which support the planning of seamless connections between bike-sharing and urban rail transport.