Evaluating the Environmental Benefits of Public Transportation Development on Urban Air Quality in China: Evidence from a Quasi-Experimental Analysis

China's swift urbanization and motorization have profoundly affected urban air quality, with transportation accounting for a substantial portion of urban air pollution. This study examines the effect of enhancements in public transportation on air quality in Chinese cities, with a particular emphasis on PM2.5 concentrations as a critical metric. Employing a Difference-in-Differences (DiD) methodology, we examine data from cities that executed substantial public transport enhancements between 2000 and 2020, contrasting them with cities that did not implement analogous measures. Findings demonstrate that enhancements in public transportation correlate with substantial decreases in PM2.5 concentrations, especially in urban areas with elevated baseline pollution levels. The results underscore the significance of sustainable transportation strategies in alleviating air pollution and enhancing public health. This study enhances the literature by delivering a thorough empirical examination of the environmental effects of public transport investments in China and has practical implications for urban authorities.