Effects of bus station density on urban air pollution: An empirical analysis based on propensity score matching

Abstract

Previous studies on optimizing bus station layouts have primarily focused on objectives such as increasing accessibility and convenience, but overlooking the effects on urban air quality, especially the accumulation effect of multiple bus stations and the mutual influence between adjacent ones. This study contributes to both the literature and practical urban planning by investigating the effects of bus station density on traffic-related air pollutants in Tongzhou through an empirical analysis using the Propensity Score Matching (PSM) approach. The results indicate that adding bus stations in previously unserved urban areas can lower CO and NO₂ levels, but may increase PM10 and PM2.5 concentrations. To best reduce CO and NO₂ concentrations, the optimal distances between adjacent stations should be 1500 m and 1250 m, and the optimal densities are 5 stations within a 2000 m radius and 2 stations within a 1250 m radius, respectively. Besides, the highest increases in PM10 and PM2.5 concentrations occur where 3 stations are within a 2000 m radius, warranting attention. These results offer empirical support for urban planners to optimize bus station layouts while considering the improvement of urban air quality. Additionally, the methodological framework of this study has potential applications in exploring the environmental impacts of various transportation infrastructures.