The vice-mayor of Beijing in charge of traffic management has resigned and been sent to the far-western region of Xinjiang as officials take drastic steps to ease chronic gridlock in the Chinese capital.

Huang Wei's resignation and appointment as vice-chairman of Xinjiang were approved Thursday, the official Xinhua news agency said -- the same day Beijing announced plans to slash the number of new cars in the city next year.

Huang, who was appointed vice-mayor in 2008, appears to have paid the price for soaring vehicle demand that has seen the number of passenger cars on the streets of Beijing skyrocket nearly 85 percent in the past five years.

The number of registered cars in Beijing stood at 4.8 million on Thursday, with 750,000 new cars hitting the already congested streets this year -- an average of 2,000 every day -- officials said.

That compares with a total of 2.6 million cars in 2005, state media said.

Beijing's air is among the most polluted in the world and the problem is getting worse amid high demand for private vehicles from its increasingly affluent residents.

The Chinese capital and Mexico City have the worst traffic jams in the world, according to a survey released by IBM in June. The two cities scored 99 out of 100 in IBM's "commuter pain index".

Authorities said Thursday they would allow 240,000 passenger cars to be registered in Beijing next year through a licence plate lottery system -- about one-third of the number of new cars registered in the capital this year.

The new rules, which took effect Friday, will see nearly 90 percent of the new licence plates given to residents.

Expectations that the government was going to restrict the number of new number plates issued next year sparked a surge in sales this month, with more than 20,000 cars sold in the first week of December, state media said.

That was more than double the 9,000 cars sold in the same period last year.

On Thursday night, auto dealers around the city stayed open until midnight so residents could buy a car before the new rules took effect, the China Daily said.

Authorities admitted that the registration cap along with other measures such as higher parking fees in the city centre and stricter enforcement of traffic rules would not automatically ease the severe bottlenecks.

"It will be difficult to dramatically improve the traffic situation in a short time," said Li Shaoming, deputy director of the Beijing Traffic Management Bureau.

"But it can slow down the pace of worsening traffic congestion."

If the current pace of growth in new cars were to be maintained, the city would have seven million by 2015 on a road network that can handle 6.7 million, state media said.