Olympics: London 2012 kicks off with football
The first event of the Olympics is to kick off later, two days before the official opening ceremony.
The Team GB women's football side will get 18 days of sport under way at 16:00 BST (15:00 GMT) against New Zealand at Cardiff's Millennium Stadium.
There were hold-ups during the morning rush hour in London as designated Games Lanes began operating.
Ahead of a planned strike on Thursday, the government says immigration at Heathrow should still be fully staffed.
Culture Secretary Jeremy Hunt said a sufficient number of shifts had been confirmed that should "get people through in the shortest possible time", despite the strike by the Public and Commercial Services (PCS) union.
The government is also trying to get a court injunction to stop the strike by workers including immigration and passport staff at Heathrow and other airports.
In other Olympics news:
- The launch of Games Lanes in London has caused confusion , with some of the lanes still open to everyone, and signs on some stretches apparently offering conflicting advice to motorists
- The Olympic flame visits Wembley Stadium as it travels 30 miles through the London boroughs of Harrow, Brent, Barnet, Enfield and Haringey. Follow day 68 of the torch relay here , during which England's World Cup-winning goalkeeper Gordon Banks, Rupert Grint of the Harry Potter films, and decathlete gold medallist Daley Thompson will be among the torchbearers
- The final dress rehearsal for the opening ceremony is due to take place later at the Olympic Stadium, in Stratford, east London
Mr Hunt will join Welsh Secretary Cheryl Gillan in Cardiff for the first event of the 2012 Games.
Team GB coach Hope Powell said opening the Games was a "great honour" and would hopefully give people "a greater appreciation of how good women's football actually is".
And captain Casey Stoney said she hoped the fixture could "raise the profile of women's football".
She added: "Hopefully we can put on a good show - but we are just focused on getting the job done."
Cameroon and heavily-fancied Brazil meet at the stadium after the GB game, and four other matches in the same competition are also taking place at Hampden Park in Glasgow and the City of Coventry Stadium.
The Olympic Route Network (ORN), made up of 175 miles of roads connecting up the main Olympic venues across the country, comes into force on Wednesday.
It is designed to make it easier for athletes and officials to get around the Games and has seen junctions blocked off, bus stops moved and parking bays suspended.
As part of the ORN, the designated Games Lanes in London will be in operation between 06:00 BST (05:00 GMT) and midnight and only open to VIPs, athletes and accredited media.
Ordinary motorists going into the lanes face fines of £130.
But the Games Lanes are intended to be flexible to traffic needs, resulting in confusion among motorists on the A40 on Wednesday morning at electronic signs suggesting they could use the lane alongside fixed signs warning that the Games Lane was being enforced.
There were traffic jams and queues on several roads including the M4, A4, and the A40 in west London; the A12 at the Lea Interchange and A13 Canning Town Flyover in east London; Hyde Park Corner and Euston Road.
"There will be a lot of disruption and London is a congested city anyway," Transport Secretary Justine Greening told the BBC News channel.
Mark Evers, Transport for London's (TfL) director of Games transport, said commuters must leave more time for their journeys.
"The worst case scenario for us is that people try to chance it and, those first few days of the Games, that they try to do what they ordinarily do - and I can guarantee all people that travel around London, those first few days of the Games are going to be really busy," he said.
TfL commissioner Peter Hendy said the early signs were positive: "We've seen a marked reduction in road traffic in the last 10 days, which is along the lines of what we asked Londoners and people who work in London to do."
Meanwhile, government lawyers are due at the High Court, where they will argue that there was a "procedural error" in the ballot of its members by the PCS union.
The PCS said it was "confident" the strike was legal and would happen.
With thousands of spectators expected to arrive at Heathrow on Thursday, it was predicted to be the airport's busiest day ever, Mr Hunt said.
Speaking to BBC Radio 4's Today programme, he said: "We can be very confident in the contingency plans that we have in place.
"As of this morning, we need 500 people to maintain a full immigration desk policy at Heathrow - which means we can get people through in the shortest possible time - and we have 584 shifts now confirmed for Thursday despite the strike.
"I am very confident that we will get people through."
But he added: "For an immigration officer - and I'm sure the vast majority of immigration officers feel this way - Thursday is one of the biggest days in their professional career ...
"It's the day when the eyes of the world will be upon them and the welcome that we're giving to the rest of the world, and the vast majority of them will want to do a really good job and show what they're capable of.
"People have their grievances, but surely the day before the opening ceremony of the Olympics is not the right time to pursue them."
Mr Hendy said: "Nearly all the athletes are here and the Olympic family are largely here, so I would imagine that any disruption to them would be fairly limited."