Toward carbon neutrality: The impact of the opening of high-speed rail on urban green total factor energy efficiency in China

As a key low-carbon-oriented transport infrastructure, the opening of high-speed rail (HSR) has been widely recognized as a critical enabler to support China’s national carbon peaking and carbon neutrality strategic targets. This study employs the dynamic network slacks-based measure (DNSBM) framework to estimate urban green total factor energy efficiency (GTFEE), accounting for both internal production linkages and cross-period production inertia. Our causal identification based on the time-varying staggered difference-in-differences (DID) model revealed that HSR opening exerts a significant positive impact on urban GTFEE, and this core conclusion remained consistent across several robustness checks, including propensity score matching DID estimation, counterfactual placebo test, exclusion of concurrent policy shocks, and alternative measurement of core variables. Heterogeneity tests further indicated that the GTFEE improvement effect of HSR opening is particularly pronounced in three subgroups: smart-city pilot cities, high-innovation-level cities, and cities with advanced industrial structures. Mediating mechanism analysis verified that HSR opening promotes urban low-carbon transformation through three core transmission paths: stimulating economic agglomeration, driving industrial structure optimization, and enhancing green innovation capacity. Furthermore, the Goodman–Bacon decomposition test for heterogeneous treatment effects confirmed that the potential estimation bias of staggered DID is negligible in this study, further supporting the reliability of our baseline estimation results.