Verbruggen acknowledged the challenge that traffic and pollution pose for the city. Beijingers purchased about 1,000 new cars a day last year, giving the city 2.6 million vehicles, half of them private.

"Staggering figures like that give an idea of the problems they have to solve," Verbruggen said. "It's an uphill battle for them."

Beijing dropped from fourth to 15th place in a Chinese survey of livable cities this year, in part because of pollution and traffic. The city has 7,000 building sites, many of them being rushed to completion ahead of the Olympics. A relay marathon went ahead last month despite hazardous smog.

Beijing's mayor regularly cites air pollution, traffic and water shortages as among his gravest problems.

"You're lucky the air quality is good during your visit," Mayor Wang Qishan told visiting Chicago Mayor Richard M. Daley on Monday. When Daley handed Wang a photograph of the Chicago skyline with Lake Michigan in the foreground, Wang said, wistfully: "Look, the sky is blue, the water clean."

Beijing has a history of taking extreme measures during important public events. In 1993, during an unsuccessful bid for the 2000 Olympics, police drove beggars and the handicapped from the city before an IOC visit. For the 50th anniversary of the People's Republic in 1999, city residents were ordered to stay home while floats and military units moved through neighborhoods for a parade.

The IOC and Beijing organizers have said they are counting on the traditional hospitality of ordinary Chinese and their enthusiasm for the Olympics to make the 2008 Games a success. But the Olympic contingency plans are testing the tolerance of ordinary Chinese, who have grown more free and assertive after two decades of economic reforms.

Beijing Olympic organizers have said privately that city residents, if given vacations during the Games, might swarm the venues rather than leave the city on holiday. Excessive security that keeps Chinese away also could spark negative media reports and spoil the atmosphere.

"The temporary administrative measures we will take will be in line with international practices," Jiang said.