License plate restriction refers to the policy controlling the increase of car licenses, so as to control the total number of motor vehicles for purpose of reducing traffic congestion and guaranteeing traffic efficiency. In China, the cities of Beijing, Guangzhou, Shanghai, Guiyang, Tianjin, Hangzhou, and Shenzhen, as well as Hainan Province, have already issued and implemented the policy of license plate restriction.By issuing a fixed number of licenses every month following the principle of either lottery or auction, the policy has played a crucial role in curtailing the growth of motor vehicles in these cities.