Beijing’s removal of up to 1.3m cars off the road in recent days in a test run of measures to ensure clean air at the 2008 Olympics was declared a success by city officials, who said major pollutants from autos dropped by up to 20 per cent.

The city reduced the number of cars on the road by about a third over four days starting last Friday, by designating alternate dates on which vehicles with odd-and-even number plates could be driven.