Reducing industrial pollution and inter-regional environmental inequality via the world's largest high-speed railway network.

Industrial pollution and the associated spatial environmental inequality increase health risks and hinder sustainable development, particularly in low- and middle-income countries. Large-scale public transportation infrastructure that connects developed and developing cities, exemplified by high-speed railway (HSR), has the potential to be an effective instrument. Here, we provide nationwide micro-level estimates for the overall and distributional environmental impacts of HSR in a middle-income context. Using over half-a-million emission records of industrial firms during the rapid expansion of Chinese HSR, the world's largest HSR program, we find significant reductions in firm emissions after HSR opening (by 5.11-13.80%). The contributions come via facilitating intercity element flows like (green) technologies and lowering emission intensities. At the aggregate level, the HSR-driven emission reductions account for 0.49-1.70% of the overall emissions during the study period. Last, we examine the geographical distributional impacts of HSR. Both our between-city and within-city analyses reveal that laggard areas benefit more from HSR connection, thereby contributing to inter-regional environmental equality.