Can Green Traffic Policies Affect Air Quality? Evidence from A Difference-in-Difference Estimation in China

Air pollution has been a serious challenge for human sustainable development. Researches show that emissions from the transport sector have been found to be a main source of air pollution in cities. Governments have implemented numerous green traffic policies to mitigate harmful emissions. However, the problem as to whether the green traffic policies are effective, and the extent to which the policies affect air quality remain unknown. This paper is the first attempt to apply a difference-in-difference method to investigate how a specific green traffic policy (in our case, the green traffic pilot cities program) affects air quality. The estimates show that the pilot program is associated with consistent reductions in annual concentration of pollutants. In pilot cities of China, the annual concentration of SO2, NO2 and PM10 decrease by 10.71 percent, 11.26 percent and 9.85 percent, respectively, after the implementation of the green traffic pilot cities program. The results show that the green traffic pilot has a noticeable improvement on air quality of the pilot cities, implying that government intervention has a positive influence on pollution prevention in the transport sector. Moreover, the green traffic system construction can be popularized in other cities to mitigate air pollution.