Millions have taken to roads and rail in what is expected to be one of the busiest travel days of the year as people gear up for Christmas.
The AA said it was expecting widespread congestion around shopping centres, football venues and ports.
It is also the last chance for people to get trains to or from London Paddington and Kings Cross, which are closed from Christmas Eve.
So far there does not appear to be any major disruption.
Earlier, there were small delays for people boarding ferries to France at the Port of Dover, but queues there have now cleared.
The AA has warned of the potential for “lengthy jams”, with some of the busiest areas on Saturday are expected to be around London’s Heathrow Airport, Manchester’s Trafford Centre and Avonmouth.
However, road congestion is likely to have peaked on Friday afternoon as drivers embarking on leisure trips competed for road space with commuters and business traffic.
“AA advice is to plan your journey and be prepared for delays,” a spokesman said.
The RAC has advised motorists to travel before 11:00 GMT or after 18:00 GMT if possible to reduce the chance of being stuck in long queues.
The British Retail Consortium said it expected high streets up and down the country to be very busy, with many people appearing to leave their Christmas shopping late this year.
On Saturday morning, the Port of Dover Travel had warned of 90-minute waits ahead of French border controls as passengers sought to get away for Christmas.
But by early-afternoon these had cleared with the port saying there was “no wait time”.
The port said there had been a surge in demand for ferries after the Channel Tunnel rail link was closed on Thursday due to unscheduled industrial action by French workers.
The Met Office has warned that poor weather conditions could also cause travel issues in parts of the UK over the weekend.
High winds are due to hit the north of Scotland and northern and central areas of England on Christmas Eve.
Two separate yellow wind warnings have been issued, saying people should expect travel disruption, damage to buildings and power cuts, while the rest of the country may see showers.
A yellow warning for rain covers much of Wales, with forecasters warning flooding and travel disruption is possible.
Widespread rain is expected throughout the UK on Christmas Day.