资源环境科技发展态势分析平台

To analyze the impact of the increase of public transport on the urban air quality will contribute to the sustainable development of urbanization. But many existing studies have not paid attention to the potential endogeneity of estimation, which comes from the fact that the deterioration of air quality would in turn affect the policies of public transport investment. This paper attempts to control this endogeneity by introducing an instrument variable of the urban built-up area into the empirical models. Using city-level data from China, our study adopts 2SLS method and conducts a series of robustness tests to ensure the estimation results more convincing and robust. The results show that the urban air quality could be improved if the city provides more buses for public transport. Moreover, after controlling the endogeneity, the marginal improving effect of increasing the public transport on urban air quality could be larger from 0.082 to 0.678. This finding indicates that the endogeneity bias is likely to cause the underestimation of the improving effect, and may result in some errors of the policy decisions of urban investment.