With less than three weeks before the Olympics begin, host city Beijing launched a traffic plan Sunday to cut its high levels of air pollution.

For the next two months, half of the Chinese capital's 3.3 million cars will be removed from the streets on alternate days.

The flow of cars was lighter than usual as motorists followed the rules on the first day of efforts to clear smog-choked skies for the Games, which begin Aug. 8.

Cars with licence plates ending in an even number took to Beijing's roads as the plan took effect. On Monday, even-numbered cars will be banned.

Other restrictions went into effect earlier in the week. Security checkpoints were set up at several roads leading into the city, causing major delays. All drivers with out-of-town registrations are being stopped and sniffer dogs are checking the contents of their vehicles.

One commuter told CBC News the extra time it takes to pass through security checkpoints is adding two to three hours to his drive into the city.

To further ease traffic, employers have been asked to stagger work schedules and public institutions will open an hour later than normal.

Two new subway lines and an airport rail link should also bring relief to clogged streets. All three lines opened Saturday, a month behind schedule.

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

With files from the Associated Press