The odd-even system based on licence plate numbers introduced since July 20 to keep vehicles off the road on alternate days has paid off, said an official in Beijing on Wednesday.

Traffic flows had improved remarkably, down by 21 percent on major avenues and average vehicle speeds up about 27 percent, said Li Jianguo, deputy director of the Beijing Municipal Committee of Communications at a press conference.

The measures, which would end on Sept. 20, were aimed at reducing the proportion of Beijing's 3.3 million vehicles on the roads to guarantee air quality and traffic movements.

Last week, Du Shaozhong, deputy director of the Beijing Municipal Bureau of Environmental Protection, said the major air pollutants, such as carbon monoxide, carbon dioxide and particulate matter from vehicles had dropped by 20 percent in Beijing from a year earlier.