[新闻背景]The British capital's famous underground train system, known as the Tube, is expected to play a crucial role in moving people around the city during the Summer Olympic Games. But the nearly 150-year-old system is already crowded and prone to mechanical failures and other delays. Workers are preparing for some of their most crowded 'rush hours' ever.

Massive overhaul

Head into the Tube and you never quite know what you might find. With 12 million passengers passing through every day - and three million more expected during the Olympics - the Tube is its own world. Trains run just minutes apart, sometimes at speeds approaching 100 kilometers per hour. The Tube even has its own cultural corners.

In recent years, The Tube has undergone a $10 billion renovation, upgrading stations and large segments of its 400 kilometers of tracks.

The official in charge of making sure it all runs smoothly during the Olympics, Mark Evers, says much of that work was focused on being ready for the Games.

"We've done everything that we possibly can do to ensure that we have a reliable system during the Games. But things can happen. But what we've done is to make sure that we have got staff on hand to deal with those incidents as quickly as possible," Evers explained. "If we did lose one of the lines serving the Olympic Park say, there are another 10 lines we can send people on. So we're confident that we will get people around.

Elaborate system

The Tube system is extensive, with 11 lines serving 270 stations, and it connects to dozens more lines of overground trains and inter-city services. It can be confusing, particularly for people who have never been here before and don't speak English, like many Olympics visitors.

Olympics organizing committee member Jonathan Edwards counsels planning, patience, and allowing extra time.

"Nobody thinks this is going to be easy. Nobody thinks there aren't going to be challenges. But we're working very hard to minimize those. And of course as always, we rely on the cooperation and the patience and good will of the public at large," he said.

The Olympic Park is at Stratford in East London, site of one of the Tube's most modern stations. It is a crossing point for five lines and these days it is adorned with signs pointing fans to the Games.

Tube officials have done what they can with signs, technology and staff training.

But the renovations and technology can't solve all the problems.

Minor delays are common, and there could well be a major breakdown, or a flood or electrical failure as happened in recent months.

And all the preparation in the world won't guarantee that everyone to makes their connections.