BEIJING (AP)

With the Olympics less than three weeks away, Beijing began restricting car use and limiting factory emissions yesterday in a final drastic effort to clear its smog-choked skies.

Under the two-month plan, half of the capital's 3.3 million cars will be removed from city streets on alternate days, depending on whether the licence plate ends in an odd or even number.

Skies were relatively clear yesterday after some morning haze, and traffic was light for a weekend, flowing smoothly on highways and city streets. But the real test will come when the workweek begins.

In addition to the traffic plan, chemical plants, power stations and foundries had to cut emissions by 30 per cent beginning yesterday. Dust-spewing construction in the capital was to stop entirely.

While the government has said it hopes to reduce vehicle emissions, one of Beijing's chief sources of pollution, it is unclear how the effectiveness of the plan will be gauged. The government has not made public a specific target for emissions levels or said how it will measure air quality.

Despite architecturally adventurous venues and $40 billion spent on improving infrastructure, China's greatest challenge has been keeping the city's air clean for the world's greatest athletes participating in the August 8-24 games. Beijing's skyline is normally shrouded with a thick, grey haze.

Already, many competitors are choosing to train away from Beijing, and International Olympic Committee President Jacques Rogge has said outdoor endurance events lasting more than an hour will be postponed if air quality is poor.

The world's greatest distance runner, Haile Gebrselassie of Ethiopia, has decided not to run the marathon event because the city's pollution irritates his breathing. To further ease the gridlock, employers have been asked to stagger work schedules and public institutions will open an hour later than normal. And those driving on the wrong days will be fined $14, a pricey penalty for many in Beijing.