Dockless bike sharing alleviates road congestion by complementing subway travel: Evidence from Beijing

Dockless bike sharing provides a flexible transportation alternative, enriching the potential of both a feeder mode for subway access and a direct substitute for subway trips. This research evaluates the interaction between dockless shared bikes and Beijing's existing subway system. Based on 3.2 million geo-coded bike-sharing trips for two weeks of May 2017, we constructed an innovative framework to distinguish subway-complementing and subway-substituting trips. Employing a generalized Difference-in-Differences identification strategy, we find that subway lines with higher bike-sharing intensity showed an 8% larger growth rate in subway ridership compared to ones with lower intensity, while the substitution effect of bike sharing on subway trips was insignificant. The rush hour road congestion level around subway stations drops by 4% for those stations with bike-sharing trips in the highest quartile. This complementarity between two green travel modes is stronger on workdays, and its congestion alleviation effect is larger in urban areas with poorer access to the existing subway network, revealing its potential to solve the "last mile" problem in areas with inadequate public transit access. We demonstrate that the synergy between dockless bike sharing and the subway system outweighs substituting effects and can help achieve a greener and healthier city.