By Michael Bristow
BBC News, Beijing
A four-day scheme that took 1.3 million cars off Beijing's streets reduced air pollution by 15-20%, officials in the Chinese capital say.
Moving around the city was also easier during the test period, with the speed of vehicles up by more than 50%.
Beijing hopes to repeat the scheme next year to cut both pollution and traffic when the city hosts the Olympic Games.
But officials ducked questions over whether the air quality was good enough for athletes taking part in the games.
Speaking at a press conference to announce the results of the car ban, environmental official Du Shaozhong declared himself satisfied.
"I am sure we will be able to ensure good air quality during the Olympic Games," he said, although he admitted four days was not long enough to make a big difference to pollution levels.
Four types of pollutants, including carbon monoxide and small particles, were tested over the four-day period, which ended on Monday.
Mr Du, who bicycled to work during the car ban, could not say whether the improved air quality would have made the atmosphere good enough to run a marathon.
International Olympic Committee President Jacques Rogge recently said endurance events could be cancelled if the air quality is not up to scratch.
Mr Du would only say that if air quality met national standards it would be good enough for "all kinds of outdoor exercises".
Fewer private cars on the road meant more people used public transport. Passenger numbers were up by 15%, it was revealed.
This meant buses - there were 800 more of them on the roads - could travel at 20 km/h (12mph) instead of the usual 14 km/h (9mph).
Chinese officials also had a kind word for the 6,500 police officers on duty during the four days, many of whom had "overcome fatigue" to ensure the test went off smoothly.
During the test period, odd-numbered cars were banned on Saturday and Monday, while cars with even-numbered registrations had to stay off the roads on Friday and Sunday.