Can urban rail transit systems alleviate air pollution? Empirical evidence from Beijing

Improving air quality across mainland China is an urgent policy challenge, while rapidly increasing use of vehicles poses a great menace to the urban population and air quality. Public transportation has received increasing attention as emissions- friendly transport options, but whether the urban rail transit system has a significant effect on curbing air pollution has been unclear, and there is a lack of explicit case studies in mainland China. Therefore, the effects of the opening of the Beijing Metro on air pollutants emissions in Beijing were quantified through a regression discontinuity design. Beijing has seen a brisk growth in its rail transit infrastructure and a downward trend of air pollution index since 2005. The regression results show that the operation of the rail transit system was observed to have a significant effect on reducing most of the air pollutants concentrations (PM2.5, PM10, SO2, NO2, and CO) but had little effect on ozone pollution. The results obtained were highly robust across a variety of tests. This study contributes to empirical evidence on the air pollutants associated with the opening of rail transit and traffic-related pollution control policy making in Beijing.