BEIJING &#8212 Despite a persistent gray haze, officials said Tuesday an exercise that removed over 1 million private vehicles from Beijing’s gridlocked streets was a success that could mean a clearer sky for next summer’s Olympics.

Humidity and wind conditions kept the pollution from dispersing, but the air during the four-day drill would have been much worse without the vehicle restrictions, said Du Shaozhong, the deputy director of Beijing’s Environmental Protection Bureau.

Air pollution has emerged as a key problem for Beijing as it gears up for the Olympics, to be held Aug. 8-24, 2008. Jammed traffic and the possibility of political protests are also concerns, although venue construction is firmly on schedule.

The traffic ban removed 1.3 million private vehicles from the capital’s perpetually gridlocked streets each day. Additional buses and subways were added as residents turned to public transportation, car pools and taxis.

Cars with even-numbered license plates were ordered off roads Friday and Sunday, and vehicles with odd-numbered plates were banned Saturday and Monday. Emergency vehicles, taxis, buses and other public-service vehicles were exempt.

Beijing had an air pollution index of between 93 and 95 during the test days, the city’s environmental protection bureau said on its Web site. According to the State Environmental Protection Agency, an index below 100 indicates excellent or good conditions.

“As the air quality during these four days reached the national standard, it was fit for all activities, including sports,” Du said.

The index hit 116 Tuesday after the test and was 115 on Aug. 16 – the day before the trial began, the Chinese statistics showed.

Chris Miller, director of the global warming campaign at Greenpeace, said the car ban was a step in the right direction for China, but he doubted whether it showed any real commitment to improving air quality.

“This is a short-term solution to what is a very acute and long-term problem. In some ways it just highlights how serious the problem really is,” he said.

Traffic controls are just one way Olympics organizers have tried to clear the skies. Officials have spent billions of dollars closing factories and moving others out of the city. Frenzied, around-the-clock construction to modernize Beijing will be curtailed ahead of the games next summer.