Urban traffic regulation and air pollution: A case study of urban motor vehicle restriction policy

Many local governments have taken various regulations to control heavy traffic and alleviate vehicle pollution emissions continuously. In practice, one of the most common and widely used regulations is the motor vehicle restriction policy (MVR policy). But it is unknown whether a motor vehicle restriction policy can effectively alleviate traffic pollution. Moreover, few studies considered the duration of the policy and distinct the effects of different types of MVR policies. In this paper, we first classify the MVR policies into consecutive and intermittent restrictions policies and analyze their different effects on air pollution based on the difference-in-differences method. Further, we take the Mediation Effect Model to verify the conduction mechanism of the impact. The result shows that both consecutive and intermittent policies can improve air quality, while the latter's effect is more significant. Moreover, as for the impact's conduction mechanism, we find that consecutive policies alleviate pollution by changing driving preference and vehicle purchase. Still, the intermittent policies alleviate pollution by promptly easing traffic jams and avoiding unnecessary vehicle emissions of the idling engine. This founding provides a decision-making basis to the government for more efficient and reasonable regulation policies.