Kindergartens, primary and high schools in Shanghai will suspend classes on heavily polluted days, the municipal government announced on Wednesday. According to a heavy air pollution emergency response plan issued on Wednesday by the municipal government, Shanghai will adopt a four-tier color alert system for air pollution. A red alert, the highest level, will be issued if the air quality index (AQI) exceeds 450 the next day. A level one emergency response will be initiated, the plan said. Under the level one emergency response, schools will suspend classes. Fifty percent of government cars that are not enforcing laws will not be allowed on the road. In addition, large-scale outdoor public activities will be suspended. High polluting industrial companies will be asked to halt production and construction sites to be closed temporarily, according to the plan. According to the Ministry of Environmental Protection, AQI of over 300 is defined as "serious pollution" and an AQI between 201 and 300 as "heavy pollution". Smog in Chinese cities this winter has come as a warning for the country to intensify its campaign against environmental damage and for local governments to take more effective measures to curb air pollution.