Can public transportation development improve urban air quality? Evidence from China

Promoting public transportation development is a crucial strategy to improve urban air quality. China's "Transit Metropolis" construction demonstration project policy ("Transit Metropolis" policy) is an important initiative around public transportation development. This paper uses the differences-in-differences (DID) method to examine the improvement effect of China's "Transit Metropolis" policy on urban air quality. The study results find that the "Transit Metropolis" policy contributes to improved air quality and that this impact tends to increase over time. The mechanism analysis finds that the "Transit Metropolis" policy improves urban air quality by slowing down private car ownership and industrial structure upgrading. Additionally, this policy has promoted the growth of the taxi industry, while the growth of the taxi industry is not beneficial in improving urban air quality. The heterogeneity analysis finds that the "Transit Metropolis" policy can improve air quality more effectively when implemented in the eastern, high environmentalemphasis, and old industrial cities. This paper provides theoretical support for the development of public transportation and improvement of air quality.