BEIJING, July 19 (Reuters) - Beijing opened three new subway lines on Saturday, delayed from a planned late-June start but just in time to carry passengers banned from their cars as the capital tries to clean up its skies before next month's Olympics.

The new lines, which will serve the international airport and the Olympic Green, will increase the city's subway lines to eight and expand their reach by 40 percent, to 200 km (125 miles), the official Xinhua news agency reported.

The 22.3 billion yuan ($3.3 billion) expansion project is part of the city's massive infrastructure plans to ensure ease of transport during the Games.

It will also boost transport options for Beijing's residents, whose rising wealth has triggered a boom in car ownership and severely worsened the city's chronic traffic congestion and air pollution.

The Beijing authorities, eager to improve air quality before the Games start on Aug. 8, will restrict vehicle use to alternate days for even- and odd-numbered licence plates starting on Sunday.

This will require an additional 4 million people to rely on the public transport system, Xinhua said.

The new trains will be able to carry 1,424 passengers each, nearly one-third more than existing lines, Xinhua quoted Zhou Zhengyu, deputy head of the Beijing Municipal Committee of Communications, as saying.

But at a news conference on Thursday, Zhou sidestepped a question about whether there would be enough time to iron out any kinks in the new lines before the Games kick off and did not say if there had been any problems with construction that might have delayed the opening, originally due by late June.

Beijing has largely avoided the problems the last Olympic host, Athens, encountered with delayed infrastructure projects, and has won praise from the International Olympic Committee for finishing venue construction work either on time or ahead of schedule.

The city has also upgraded trains on existing lines, the first of which dates from the 1960s, although some trains and stations will remain without air conditioning by the time the Olympics come in August, one of the hottest months of the year. ($1=6.816 Yuan) (Reporting by Beijing Newsroom; Writing by Edmund Klamann; Editing by Jeremy Laurence) (For more stories visit our multimedia website "Road to Beijing" at http://www.reuters.com/news/sports/2008olympics; and see our blog at http://blogs.reuters.com/china)

AlertNet news is provided by