LONDON — Keep calm and queue up.

As Olympic spectators put the city’s transportation infrastructure to the ultimate test, that seems the unofficial motto of the London Games. Crowds have waited for London Underground trains at key stations linked to the Olympic Park and other venues. Transport for London warned commuters to avoid London Bridges station Monday, expecting a crush of 50,000 equestrian spectators headed to Greenwich Park. Meanwhile, signs at St. Pancras International Station directed passengers to a waiting area with a big screen broadcasting Olympic action, though there has been no need to line up yet.

With one of the world’s largest and oldest public transit systems, London knew transportation would be the greatest logistical challenge of the Games. Transportation officials anticipated one million extra trips per day during the Olympics, adding to the 3.5 million that regularly tax the capital’s road and rail networks. To handle the increased demand, London invested more than $9 billion in system upgrades, focusing on the lines and stations that lead to venues.

Still, there have been significant travel issues leading up to the Opening Ceremonies and during the early days of competition, highlighted by lengthy delays on the high-speed Javelin train designed to whisk spectators from St. Pancras International Station to the Olympic Park in just under seven minutes. On Tuesday afternoon in a packed Olympic Park, electronic signs alerted spectators to severe delays on the Javelin train and suggested alternate routes. On Sunday, hundreds of soccer fans headed to Manchester for matches found themselves stranded in London or forced to sit on train floors because of overcrowding. And after a fire alert on the Central Line Tuesday, underground train service was temporarily suspended on a key link to the Olympic Park.

With commuters back in the mix during the work week, transportation officials warned passengers “not to chance it” and expect a smooth-running system.

‘No city under normal circumstances ever tests itself like this.’

“No city under normal circumstances ever tests itself like this,” said Sebastian Coe, chair of the London Organizing Committee of the Olympic Games (LOCOG). “You have to see the complexity of the project, the ability to bring to the table 26 simultaneous world championships with all the operations and integration around it for competitors and people coming to London.”

Because so much is happening in so many places, transportation experiences often come down to timing and chance. Some spectators travel uneventfully to venues, while others face major service disruptions and congested trains. Despite near-constant travel alerts and status updates for every line, the London Underground, locally known as the Tube, is particularly unpredictable. With parts of the Tube dating to 1863, the system is notoriously cranky, and commutes rarely go smoothly under the best of conditions.

It appears many fans heeded the advice of transportation officials and added 90 minutes or more onto typical travel times on the Tube.

Traveling with his wife and son to table tennis at ExCel Arena, David Bisby of Biggleswade, England, said their ride to the venue had been “quite easy with no holdups,” but that they “allowed extra time to get there because when you come to London it’s always unpredictable.” Like others, Bisby did not want to miss any action after spending a lot for tickets. That said, some fans on the busiest train lines acknowledged leaving events early in hopes of avoiding trains slowed by a mass exodus. Many spectators also praised the work of the police and Transport for London workers who directed crowds through potential bottlenecks on the Tube.

“We went to Wembley Stadium on the Tube and it was totally fine,” said Ceylon Hickman of Flitwick, England. “The police were on horses and really organized. They stopped us when the station was overcrowded. They let the station clear out, then let us go through.”

To alleviate confusion and minimize man-made holdups, there is no shortage of assistance or signage for Olympic visitors. At Tube station entrances, representatives from Transport for London help passengers navigate the system. Upon exiting stations, Olympic volunteers are never far, ready to direct passengers to different venues.

On the streets, outfitted in bright purple and pink, 8,000 Team London Ambassadors patrol 43 visitor hot spots, also providing directions and transit advice. Armed with iPads and maps and dressed in bright pink vests, Transport for London Travel Ambassadors help visitors with everything from directions to renting bikes from public docking stations.

Additionally, London has made use of technology with daily updates and warnings on traffic at the “Get Ahead of the Games” website. “Traveling to the Olympic Park?” an alert asks. “Avoid the queues by taking the District Line to West Ham & walk along the Greenway.” Since the beginning of July and in conjunction with the website, Mayor Boris Johnson has warned Tube passengers about increased pressure on the system during the Olympics and advised, “Don’t get caught out.”

On Monday, the transit system faced its first true test as commuters joined the organized chaos. And, to the surprise of many, the morning and evening commutes went relatively smoothly. Although trains and buses were more crowded than usual, Londoners and visitors muddled through. The next big test comes Friday when the track and field competition starts with 80,000 fans expected to fill Olympic Stadium. Grumbling from Londoners that began well before the Opening Ceremonies may return at that point.

When Olympic transportation plans were announced, local workers thought their needs were ignored. “Everybody is angry,” said Javitha Mahendrarajah, who commutes from Bayswater to Kensington for her job as a cashier. She mentioned that her friends worried about penalties for arriving late to work on trains slowed by confused tourists. She also complained that the tourists were “renting all the Boris bikes,” the London equivalent of the Hubway bike sharing system, that commuters could have used as an alternative to the crowded Tube.

“A lot of people are getting even more angry because of more delays happening,” said Mahendrarajah. “Everyone wants to leave. I haven’t met anyone yet who’s like, ‘Yeah, Olympics!’ ”

Underscoring how completely the Games have disrupted regular life, an electric sign outside Regent’s Park reads: “Avoid driving Central London until 14 August.” Other electric signs flash alerts about when the “Games Lanes” are in full use. Running beside regular traffic lanes, 30 miles of “Games Lanes” are reserved for transporting VIPs, athletes, and media, further angering commuters and compounding traffic problems in the city. Particularly peeved about the lane restriction, London cabbies held a protest at Hyde Park Corner in central London hours before the Opening Ceremonies. All drivers face a $200 fine for improperly using the “Games Lanes,” even if unintentionally.

The International Olympic Committee has required host cities designate special “Games Lanes” in the wake of severe traffic problems at the 1996 Atlanta Olympics, where bus drivers got lost and athletes nearly missed competitions.

But even with special transportation, there are no guarantees of an easy time for athletes or other members of the “Olympic family.” Going from Heathrow Airport to the Athlete’s Village by special Olympic bus, US 400-meter hurdler Kerron Clement found himself traveling in circles. He first tweeted: “Um, so we’ve been lost on the road for 4hrs. Not a good first impression London.” He sounded a little more desperate in a second tweet when he tapped out: “Athletes are sleepy, hungry and need to pee. Could we get to the Olympic Village please.”

A group of Australians also got an unplanned 3½-hour tour of London when they arrived, driving past Buckingham Palace and the Houses of Parliament on the way to the Olympic Village with a lost driver who couldn’t operate the GPS navigation system on the bus.

Meanwhile, some athletes bravely ventured out on public transportation. Czech badminton player and flag bearer Petr Koukal complained about the 80-minute, one-way commute to his practice venue. But he didn’t mind a small misadventure while trying to find St. Pancras International Station.

“We got lost right now on the way back because I was distracted by a local woman who was hitting on me,” said Koukal. “I was following her. I thought she was going the right way, but it turns out she wanted to take me somewhere else. Probably. I wish. She was nice and point the way back and said, ‘I hope you won’t be distracted on the court.’ ”