BEIJING -- The Beijing Municipal Government will soon issue an emergency response program requiring alternate driving days for cars with even- and odd-numbered license plates in case of lingering smog, Xinhua has learned.

When the city issues a red alert for air pollution, the system will be initiated to reduce pollution, according to the Beijing Municipal Heavy Air Pollution Emergency Response Program.

Moreover, 30 percent of government cars of various levels will be halted, and schools in kindergartens, primary and high schools will be suspended during such polluted days, under the program.

It was passed on Wednesday at the meeting of the Standing Committee of the Beijing Municipal Committee of the Communist Party of China, and will soon be released to the public by the Beijing Municipal Government.

If the ban under the red alert is initiated, 2 million more people are expected to rely on the capital's public transport system. In that case, the city will increase bus frequencies by 21,000 to 25,000 over all, and the subway operation time will be extended by half an hour in the evening, said Fang Li, deputy chief of the city's environmental protection bureau.

According to the emergency response program, the city will adopt a four-tier color alert system for air pollution. The red alert, the highest level, indicates serious air pollution for three consecutive days.

To prevent the most serious cases from happening, industrial plants will be ordered to halt or reduce production to curb emissions, and building construction, fireworks, and outdoor barbecues will be prohibited if an orange alert is issued.

An orange one, the second highest, means heavy or serious air pollution alternately for three consecutive days.

According to the Ministry of Environmental Protection, air with an Air Quality Index (AQI) of over 300 is defined as "serious pollution" and an AQI between 201 and 300 as "heavy pollution."

Vehicles in the city are considered a major contributor to Beijing's smoggy skies in recent years.

A report  by a research team from the Chinese Academy of Sciences revealed that vehicle exhaust fumes are among Beijing's top sources of air pollution, contributing 22.2 percent of PM 2.5 particles in the city, exceeding the figure for industrial emissions.