Millions took to roads and railways on what is expected to be one of the busiest travel days of the year as people prepare for Christmas.
The AA said it expected widespread congestion around shopping centres, football stadiums and ports.
So far there does not appear to be any major disturbance.
Earlier, there were minor delays for people boarding ferries to France at Dover Port, but the queues there have now been removed.
The AA warned of the potential for “prolonged bottlenecks”, with some of the busiest areas expected on Saturday to be around London Heathrow Airport, Manchester's Trafford Center and Avonmouth.
However, road congestion is likely to peak on Friday afternoon, as drivers escaping for Christmas compete for road space with commuters and commercial traffic.
A spokesperson said: “The AA's advice is to plan your journey and prepare for delays.”
The RAC 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 expects high streets across the country to be very busy, as many people appear to be leaving for their Christmas shopping late this year.
On Saturday morning, the Port of Dover warned Travel to wait 90 minutes before monitoring the French border.
But by the afternoon, it had been cleared, with the port saying there was “no waiting time.”
The port said there was a rise in demand for ferries after the Channel Tunnel railway line closed on Thursday due to an unscheduled industrial strike by French workers.
The Met Office warned that adverse weather conditions could also cause travel problems in parts of the UK over the weekend.
Strong winds are expected to hit northern Scotland and the northern and central regions of England on Christmas Eve.
Two separate yellow wind warnings were issued, saying people should expect travel disruption, building damage and power outages, while the rest of the country could see rain.
A yellow rain warning covers most parts of Wales, and meteorologists warn of the possibility of flooding and travel disruption.
Widespread rainfall is expected across the UK on Christmas Day.
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