BEIJING -- Liu Jingmin, vice mayor of Beijing, said Thursday that the city is still considering when to keep some vehicles off the road according to their license plate numbers.

"One thing is certain, the practice will not be adopted too early," said Liu, a member of the11th National Committee of the Chinese People's Political Consultative Conference (CPPCC), which is convening its first annual session.

According to a traffic control scheme, odd and even numbered vehicles will be ordered to stay off the road in turn on some special occasions, in a bid to reduce pollution and congestion.

Liu denied the possibility that such a scheme would be carried out beginning May to avoid affecting the residents' life too much.

"Only when the Games is drawing near will we adopt the practice," Liu told journalists.

Last year, the Beijing Municipal People's Congress authorized the municipal government to adopt some "unconventional measures" in terms of social security, road traffic, workplace safety, environmental protection, food quality and advertisement administration in the run-up to and during the Beijing Olympic Games.

From August 17 to 20 last year, Beijing took a four-day test to see whether the exclusion of 1.3 million vehicles off the city's roads each day would be effective in reducing air pollution and traffic jam.

Motor vehicles with even or odd numbers of license plate took to the road by turns. However, taxis, buses and emergency vehicles were not restricted.

The air quality index in Beijing on August 17, 2007, stood at 91 (51 to 100 represents "fairly good" air quality), down from the previous day's figure of 115, which is classified as slightly polluted. In the meantime, many people found they were driving at faster speeds.

Beijing Olympic Games will be held from August 8 to 24.