Do driving restrictions improve air quality: Take Beijing-Tianjin for example?

To manage air quality, Tianjin introduced driving restriction (DR) in 2014 and new driving restriction (NDR) in 2018. Ever since February 22th, 2018, private cars that belong to Beijing have been treated equally as local cars of Tianjin. However, existing studies rarely compare the effects of driving restrictions in different cities. In this paper, using the regression discontinuity design (RDD) model and urban air quality monitoring data from Beijing and Tianjin during the period 2014 to 2018, we explore whether driving restriction policies can improve air quality in Beijing and Tianjin. The main results are as follows. (1) Our results of regression discontinuity design revealed that the DR had no obvious improvement in the air quality in Tianjin. Furthermore, the effect of the DR decreases along with its implementation. (2) The implementation of the DR in Tianjin had slight improvement in air quality in Beijing, which mainly reduced emissions from cars. In other words, the DR brought about weak externality. (3) We found that the effect of NDR on the air pollution was limited in both Tianjin and Beijing. To sum up, we compared the NDR with DR and found out that the DR was more effective in the short run, while the NDR could work well in the long term.