People travelling towards east London for the start of the Olympics suffered main line and Tube delays today.
One of the hold-ups was at North Greenwich where the Games' gymnastics and basketball is being held.
The North Greenwich problem was a signal failure on the Jubilee line - just two stops from the main Olympic station at Stratford.
Those heading to London from East Anglia were delayed by a broken-down train at Ingatestone in Essex.
This caused hold-ups for Greater Anglia train company services into London's Liverpool Street.
There were also delays into another major London terminus - Euston.
These were caused by a signalling problem at Bletchley in Buckinghamshire which affected passengers on London Midland, Southern, and Virgin Trains services.
Also, First Capital Connect and Southeastern train services were affected by a lineside fire at Herne Hill in south London.
Earlier, a train designated by Southeastern to mark the start of the official high-speed London to Stratford Javelin services left St Pancras station five minutes late.
Southeastern said the 7.04am had departed at 7.09am as the booked driver was ill and had to be replaced.
Network Rail (NR) and the Association of Train Operating Companies (Atoc) said a total of nearly 444,000 extra main line train seats were being provided today.
In all, four million seats were on offer, thanks to the running of extra services and longer trains.
NR and Atoc said that at noon, 92% of services were running to schedule across the network.
Late-night trains will run after tonight's opening ceremony. For example, the last train from London Paddington to Oxford leaves at 2.17am and the last from Euston to Manchester at 2.30am.
On the roads, there was congestion around the Thames bridges in London as the Olympic Torch Relay travelled down the river today.
There were also jams along some of the Olympic traffic-only Games Lanes, including the A40 in Ealing, west London.
Roads were also congested around St Pancras station and around St John's Wood in north-west London where the Olympic archery competition began at Lord's cricket ground today.
Traffic heading for London on the M1 was badly held up around mid-day after a multi-vehicle accident in Northamptonshire.
Three lanes northbound and two southbound were closed between junction 16 west of Northampton and junction 18 east of Rugby. The northbound section was only able to stay open through traffic using the hard shoulder to get past the accident scene.
A spokesman for traffic information company Inrix said: "These delays will impact traffic heading to London for the Games today.
"The advice is for traffic heading from the West Midlands or north-west England to take the M40 instead. For those travelling from Yorkshire or north-east England, we advise drivers to take the A1."
On the Tube there were minor delays on the Victoria line due to staff illness.
Some public transport routes today were far less busy than normal, with would-be travellers appearing to heed the advice of Transport for London (TfL) to avoid central London during the Games.
TfL said the area around Stratford has been busy from early today and that there had also been congestion at some Games lanes sites.
"Passenger and traffic levels today are about where we expected them to be," said a TfL spokesman.
He went on: "It will be busier tomorrow when there will be a number of events including cycling."