BEIJING - City officials yanked hundreds of thousands of cars off Beijing's streets Friday to test whether a partial car ban could clear health-threatening smog and ease gridlock during next year's Olympic Games.

The test is a challenge for Beijing Olympic organizers and city authorities to see if they can balance the need to dampen severe pollution without angering a growing middle class. Upwardly mobile Beijing residents have quickly grown used to the comforts of driving, as private car ownership exploded in the past five years.

"We just got used to driving and suddenly we're not allowed?" said Zhang Jie, a stock trader who bought her first car -- a Chinese-made Chery QQ subcompact -- last year.

"It's not good to forbid so many people from driving," said Zhang who planned to take a taxi to work. "I feel like the government should be able to come up with a better plan than this."

The four-day ban uses an odd-even license plate number system, so only vehicles with license plates ending in odd numbers were allowed on the roads Friday, the 17th of the month.

Sun Weide, deputy director of the Beijing Olympic organizing committee, said the system was intended to take 1.3 million cars off the road every day -- more than a third of the city's 3 million vehicles. The official Xinhua News Agency said the plan would remove 400,000 private cars daily.

The Beijing Traffic Police said they could not immediately confirm the figure.

Subway cars were tightly packed with commuters during the morning rush hour. Traffic on the main roads flowed at a brisker pace than normal, while police maintained a normally visible presence.

Traffic and air pollution have emerged as key logistical problems for the city as it gears up for the games. Beijing has been adding cars at the rate of about 1,000 new vehicles a day, a pace that is not expected to slacken over the next year. International Olympic Committee president Jacques Rogge warned last week that some events might have to be postponed if the city did not clean up the pollution.

To get drivers to heed the ban, the city was using a combination of penalties and persuasion. Violators were to be fined $13 if caught driving in the city and ordered to return home, a Beijing Traffic Police spokesman, who would only give his surname, Yan, said Thursday.

State-controlled media, including Beijing's popular traffic radio station, broadcast appeals all week, reminding drivers that by obeying they were participating in the Olympics.

Zhu Xiaobin, chairman of the 4,000-member Zhu Shanren car club, said his members understood the need for the restrictions and would follow them. But he suggested that people who abstained from driving during the games should be given a reduction of the road maintenance fees all car owners are required to pay.

Despite some grumbling, drivers mostly complied with the ban on Friday.

"It's for the Olympics so we've got to do it," said Li Hui, a consultant and car owner who added he would take a taxi to work. "This is a big thing for our country. Everyone should support it and put the greater good ahead of their own personal interests."