BEIJING'S plan to restrict car use to improve air quality for the Olympics kicked into high gear yesterday.

Traffic flowed smoothly in most areas, although skies were hazy, a sign that it could be several days before the impact of the measures - which also include constructions cutbacks and factory closures - is noticeable.

Under the two-month operation that began on Sunday, half of the capital's 3.3 million cars will be removed from city streets on alternate days depending on whether their license plates end in an odd or even number.

Sun Weide, spokesman for Beijing's Olympics organizing committee, said the plan should reduce vehicle emission by about 63 percent.

Sun said changes in air quality will be monitored by experts from the city's environment protection bureau.

Already "it can be easily felt that traffic is less heavy now and the number of vehicles on the road is clearly smaller," Sun said. "We predict that we could achieve our goal."

Yesterday, traffic moved at a steady pace along main thoroughfares and highways.

"Before, we would be at a dead standstill," said a taxi driver surnamed Zhang. "Now it's better."

Drivers with even-numbered plates were forced to take public transportation, where crowds remained surprisingly manageable.

"It seems that the subway isn't as busy as I expected. There are fans and air conditioning, so you don't feel very hot," said Chen Songde, who normally drives to work.

In addition to the traffic plan, chemical plants, power stations and foundries had to cut emissions by 30 percent from Sunday. Dusty, noisy construction in the capital had to stop entirely.

Those caught driving on days they shouldn't will be fined 100 yuan (US$14).

Some 300,000 heavily polluting vehicles - aging industrial trucks, many of which operate only at night - were banned from July 1.

The government has also improved public transportation options for the estimated 4 million extra people who will be off the roads because of the traffic plan, Xinhua news agency said.

Two new subway lines and an airport rail link were open over the weekend, with the number of passengers on the three routes expected to reach 1.1 million daily during the Olympics.

In all, eight lines will transport up to 5 million people daily during the Games, the company that runs the Beijing subway said.

The subway may not have been as crowded as originally expected because employers have been asked to stagger work schedules, and public institutions will open an hour later than normal.

The city also plans to add up to 3,000 more buses by the time the Games start.