Abstract: Many cities in China have implemented to take traffic restrictions policy to alleviate road congestion and control vehicle pollution. However, there are few studies which focus on the effects of different kinds of restriction regulations on air pollution from the perspective of cities. In this paper, the policies are classified as general restriction and specialized restriction. Based on the Difference-in-Difference model using panel data of provincial capitals and municipality cities in China from 2001 to 2017, the effects of different traffic restrictive regulations on PM_2.5 emission are evaluated. The results presents as follows. Firstly, the vehicles have become one of the main sources of urban PM_2.5 emission, and vehicle restriction measures are increasingly used during the urban air pollution control. Secondly, both general restriction and specialized restriction can effectively reduce PM_2.5 emission, but the effect of specialized restriction policy is more significant. Thirdly, the intensity of traffic restrictions, like the factors of the restricted area and the restricted numbers of vehicle, can apparently influence the policy effects. Fourthly, according to the robustness test, the restrictive policy is still valid after removing the effect of sample "Beijing city" and all cities with "purchasing restrictive" policies. The impact of the vehicle restrictive regulation on mitigating PM_2.5 emission is demonstrated, and the findings can provide more efficient and reasonable policy supports for the decision-makers.

Key words: PM_2.5 emission, vehicle restrictive policy, Difference-in-Difference model, air pollution, traffic emission regulation