Beijing is noticeably less congested following the four-day scheme that yanked 1.3 million private cars off the streets on Friday.

The aim of the scheme is to test whether or not a partial car ban could clear the health threatening smug during next year's Olympic Games.

Previously the Olympic chief Jacques Rogge had said that air pollution could lead to some events being postponed at the 2008 Beijing Games.

The test is a challenge for Beijing Olympic organizers and city authorities to see if they can reduce severe pollution without angering a growing middle class.

City residents, who are being forced to take public transport during the test period, generally appeared to support the project.

During the four-day test period, cars with registration plates ending in odd and even numbers will each be banned from the roads for two day.

A similar experiment was carried out last year during a forum for African leaders held in Beijing.

Beijing is one of the world's most polluted cities and poor air quality is partly blamed on the city's three million cars.

HE/KB