Updated

Beijing is asking residents to leave their cars at home for one day a month to help improve air quality, the city environmental agency said Tuesday.

The voluntary campaign, targeting more than 200,000 members of Beijing's driving associations, aims to boost the number of days with 'fairly good' air quality in the capital to 238, five more than last year, said the statement from the Beijing Municipal Environmental Protection Bureau.

Beijing added new vehicles at the rate of about 1,000 a day last year, giving the city a total of 2.6 million vehicles, half of them private cars, officials with city transportation agencies said earlier this year.

Vehicle emissions are the leading cause of Beijing's air pollution, with vehicles spewing out 3,600 tons of pollution each day, it said.

Beijing launched a program to reduce air pollution in 1998, when the city had only 100 days with fairly good air quality each year, it said.

The president of the Friends of Nature environmental group, a co-sponsor of the initiative, told The Associated Press the request was symbolic but better than nothing.

"We don't keep so much hope on this," said Liang Congjie. "But we think it will make a little difference."