Exceptions to the restrictions will include taxis, buses and emergency vehicles, said a statement on the website (www.bjjtw.gov.cn) of the Beijing Municipal Committee of Communications.

The statement said the intention of the restrictions was to improve traffic flows and air quality during the Olympics and Paralympics, and to fulfill Beijing's commitment to host a "green Olympics".

In the statement, the municipal government said the measure would be enforced throughout the city until Aug.28, but only in areas within the Fifth Ring Road and three freeways connecting downtown Beijing to the airport, Badaling and Chengde from August 28to September 20.

The municipal government is also to ban all motor vehicles that fail to meet the European No.1 standard for exhaust emissions as well as trucks registered outside Beijing without special permits from July 1.

It is believed the temporary traffic controls will put 70 percent of cars owned by government departments and institutions in the city out of use.

To compensate motorists for the restrictions, all vehicle owners will be exempted from taxes and road maintenance fees for three months, costing the government 1.3 billion yuan (US$186 million).

During a test of the controls from Aug. 17 to 20 last year, about 1.3 million vehicles were taken off the city roads each day and the emissions discharged were cut by 5,815 tons, according to a report by the Beijing Municipal Bureau of Environmental Protection.