In one of its most expansive traffic campaigns ever, the city flooded state-controlled media with appeals not to drive, sent text messages on mobile phones, banned construction and ordered government agencies to halve car use, the officials from three city offices said.

The combination of control and persuasion proved remarkably effective, taking off the city's streets about 30 percent, or 800,000, of the capital's 2.8 million vehicles during six days of meetings between Chinese and African leaders that ended Monday, the officials said.

"People joked that it was impossible not to receive traffic information even if you didn't want to know about it," Zhang Jingchun, a spokesman for the Beijing police's traffic management bureau, said at a news conference to highlight the campaign's success.

While Beijing prepares to test the readiness of its Olympic sports facilities by holding sporting events in the coming months, the China-Africa summit served as a tryout for one of the thorniest logistical problems the city is facing for 2008,its often gridlocked traffic.

"Next year we will host a series of test events in the run-up to the Olympic Games as well as other major international conferences. The summit offers us very important experience in organizing such major events," Liu Xiaoming, spokesman for the city's Transportation Commission, said at a news conference.

The arrangements were not trouble-free. The Africa summit was the largest high-level diplomatic gathering Beijing has hosted, with presidents, dignitaries and entrepreneurs from 48 African countries shuttling around the capital. Police shut down roads to make way for the motorcades, forcing traffic on to smaller streets that then easily clogged.

But the generally positive result lends encouragement to a city of 13 million that is undergoing economic and building booms while trying to ramp up for the complex task of staging an Olympics. Soaring private car ownership and swelling fleets of official vehicles often leave the city choking in traffic and the health-threatening smog it generates.

Traffic and pollution routinely top the International Olympic Committee's list of concerns about 2008 and were raised at a meeting last month with Beijing Olympic organizers. Despite investing hundreds of millions of dollars on new roads and subway lines, city officials have acknowledged that special traffic and environmental controls would be needed for 2008.

In trying to allay concerns, officials with the Beijing Olympic committee have told recent visitors that the Africa summit would prove the city was up to the task.

"This has relieved me of a lot of the fears of how they're going to do this because they've given me a demonstration," said Steven Roush, a senior U.S. Olympic Committee official who was in Beijing last week to book housing and training facilities for the American team for 2008. "This is my tenth day here, and it's the best weather I've seen."

Beyond the summit, the measures taken to smooth traffic underscore how the communist government has had to adapt to international scrutiny and a society empowered by capitalist reforms.

Chinese leaders once governed by fiat, for example ordering people to stay home during a massive military parade to celebrate the 50th anniversary of communist rule in 1999.

Warned by the IOC that heavy-handed measures could tarnish China's reputation, Beijing organizers have promised that Olympic contingencies would be in line with international norms.

For the Africa summit, Liu, the transportation official, said no compulsory restrictions were issued to private car owners. Only government fleets were given orders, with city offices told to keep 80 percent of their cars off the streets and central government agencies 50 percent.

Rather, the city mobilized the media and environmental activists to appeal to Beijingers' sense of hospitality. People were advised to take public transport and informed of road-closings. The popular state-owned Beijing Traffic Radio ran public service announcements from Vice Mayor Ji Lin, who asked motorists to cooperate, saying the summit schedule was planned "down to the second."

Particularly targeted were the city's more than 400 auto clubs and their largely upwardly mobile membership of private car owners.

The city Environmental Protection Bureau called in executives with the car clubs, requesting they post notices on their Web sites and send mobile phone messages to their members, two car club officers said.

"People knew it was for the image of Beijing and the country," said Zhou Chunxing, office manager of the Target Action Car Club, which has 1,000 members. "This time, the government has set an example by keeping its cars off the road first, so people were willing to follow suit."