Facing rapid motorization, many Chinese municipalities are implementing policies that restrict car ownership or use. However, there is significant variation in terms of which cities adopt these policies and when. This research systematically investigates what factors prompt local governments in China to adopt these car restriction policies. We collect a database of car restriction policies as well as economic, demographic, land use, and transportation indicators for 287 Chinese municipalities from 2001 to 2014. We adopt a mixed methods approach that combines a qualitative investigation of stated objectives and legislative precedent within policy documents with a quantitative duration model of policy adoption. We find that the adoption of comprehensive car ownership and use restriction policies across Chinese cities primarily responds to local air pollution and secondarily to car ownership and congestion. Policy adoption additionally responds to local subway line constructions. Local economic power and population size do not effectively explain policy adoption. Idiosyncratic effects at provincial or city levels are important, although the underlying mechanisms by which these network effects manifest remain unclear. Broadly, our findings suggest that problem solving and network effects both contribute to the adoption of car restriction policies across China’s cities and that the legal policy documents reliably illustrate the motivations of these policies.