Does high-speed rail improve China's urban environmental efficiency? Empirical evidence from a quasi-natural experiment

Whether high-speed rail (HSR) can promote the coordination between the economy and environment is a critical issue that needs to be investigated. We used balanced panel data of 281 prefecture-level or above cities in China from 2005 to 2017 to consider the opening of HSR as a quasi-natural experiment. We integrated the difference-in-differences (DID) model, the spatial difference-in-differences (SDID) model, and social network analysis (SNA) to empirically investigate the impact of HSR on urban environmental efficiency (UEE). The results showed that HSR significantly improved UEE by 4.6% annually during the study period, although the effect of HSR on UEE exhibited a time lag and varied dramatically in different cities. An analysis of the mechanism showed that the effect of technological innovation and the structural effect brought by the opening of HSR were the main contributors to the improved UEE. Further analysis showed that HSR service centrality also significantly improved UEE and HSR opening and HSR service centrality both had positive spatial spillover effects on the UEE of neighboring cities. Several policy implications are proposed accordingly to make full use of the advantages of HSR to improve UEE for China.