Key rail links to London's Olympic Park suffered major disruption on Monday, raising fresh concerns about the British capital's creaking transport network just four days before the Games.
Traffic jams also built up on several main roads leading into London amid work to prepare them to be special link routes to the Games, which begin on Friday.
During the Monday morning rush hour delays hit two lines on the Underground subway system, the Jubilee and Central Lines, while a key overground rail link and the elevated Docklands light railway system also had problems.
All four lines go to Stratford, the station in east London where the Olympic Park is located and where hundreds of thousands of passengers will be disembarking in coming days.
"I think the Tube might struggle a bit during the Games to be honest," said Steve Claxton (55) a passenger at Liverpool Street rail station in central London, a key hub for lines heading to the Olympic Park.
"I've just flown in from Bangkok and the network there seems a lot more efficient. They have a train called a Sky Train from the airport to the centre and there are no delays on it," Claxton said.
A spokesman for Transport for London, the capital's public transport authority, said the capital had a "very robust transport network."
"Things happen on the Underground but there are always alternative options open to passengers," the spokesman said.
Drivers meanwhile faced delays of up to two hours on three major roads into London, including one, the A40, which links the capital to England's second biggest city Birmingham where a number of Olympics teams are staying.
Special lanes for Olympic traffic have already opened on the M4 motorway which leads from London's Heathrow Airport, the gateway airport to the Games, and will open on Wednesday on other routes.