China plans to restrict purchases of vehicles in a bid to curb air pollution fueled by its congested roads.

Four cities, including Beijing and Shanghai, have already taken measures to rein in motor vehicle emissions by restricting purchases of cars through lotteries and auctions of a limited number of license plates.

The China Daily newspaper quoted Shi Jianhua, deputy secretary general of the government-backed China Association of Automobile Manufacturers, as saying that eight more cities are likely to announce similar policies.

The port city of Tianjin, near Beijing, Chongqing in the southwest and industrial powerhouse Shenzhen, are among those who are expected to follow suit.

The policies might cut vehicle sales by 400,000 units, or 2% of total domestic sales, and have a “certain impact” on the country’s economic growth, Shi said, according to China Daily.

Such restrictions were unlikely to have much effect on pollution because there are already too many cars on the roads, Zhao Jian, a transport expert at Beijing’s Jiaotong University’s School of Economics and Management.

“Even with proper enforcement, the policy still won’t solve the air pollution problem, neither will similar measures in other cities,” Zhao said.

Last year, around 13 million cars were sold in China – the biggest car market in the world, reports China Post.