Rail services to one of the key Olympic stations were delayed on Wednesday morning, while there were also hold-ups at another major London terminus.
Some passengers were stuck for around 30 minutes outside London Bridge station due to "operating problems".
The difficulty led to delays to services run by the Southern train company in and out of London Bridge in the morning rush-hour. A spokesman for Southern Railway said the delays were caused when a train was signalled into the wrong platform at the station. The 10-carriage train arrived at a platform intended for trains with eight carriages.
The spokesman said: "It meant the train had to be sent back along the track, which caused congestion."
Passengers faced delays of about 20 minutes before services returned to normal at 8.30am.
London Bridge is one of the major Olympic hub stations, dealing not only with arriving commuters in the morning but those leaving to go to Olympic events.
There were also problems at Cannon Street station where a signalling problem meant fewer trains to and from this main London terminus. This affected services run by the Southeastern train company.
There were also travel difficulties on the Tube, with a signal failure at Turnham Green in west London resulting in no District line services between Earls Court and Richmond/Ealing Broadway.
Meanwhile, a recorded message from London mayor Boris Johnson warning passengers of "huge pressure on the transport network" that was being played in London Underground stations and on buses has been discontinued. A Transport for London (TfL) spokesman said it was not part of a new strategy and it was planned that the message would only be played for a certain time.
TfL said that Tube passenger numbers were up by 7.5% on Monday compared with a normal Monday, with Docklands Light Railway up by a record 65%.