Shaanxi provincial government issued an emergency plan stipulating that 30 percent of official cars must be off the road during heavy pollution, China Daily learned on Monday.

According to the Contingency Plan for Heavy Urban Air Pollution Days, departments at all levels in the province are required to stop using at least 30 percent of their official cars during heavy pollution in urban areas.

And social vehicles should also be controlled by the even-odd license plate plan in the cities where conditions for the plan are ready.

Heavy pollution means that the air quality index reaches 301 to 499 or over.