Traffic restrictions came into affect in Beijing on Sunday in an attempt to improve the capital's air quality and traffic situation for next month's Olympics, the China Daily reported.
The Beijing authorities are likely to announce the special measures for the August 8-24 Games soon, the city's environment authority said.
Li Xin, a senior engineer who has drawn up the plan for the Beijing Environmental Protection Buearu, said: "We will implement an emergency plan 48 hours in advance if the air quality deteriorates during the August 8-24 Games."
Talking to China Daily over the phone, she said the environment authority would inform the public as early as possible about the details of the plan.
Zhu Tong, an environmentalist, has suggested keeping up to 90 percent private vehicles off the streets during the Games as part of the plan.
Only vehicles whose license plate ends with the last digit of the date should be allowed to hit the road, he said.
eijing began its biggest ever pollution-cleaning campaign on July 20, imposing the even-and-odd license number rule for vehicles. This means vehicles whose number plates end with an even number drive on one day, followed by those that end with an odd number. Only about half of the city's 3.3 million vehicles have hit the roads on any given day since then.
But the recent hot and sultry weather, with occasional breeze, and the still high emission level, have raised fresh concerns over the weather during the Games.