Millions of people are expected to take to the roads on what is expected to be the busiest day of the Christmas getaway.
Airports and ports are also full of people travelling to spend the festive period overseas.
A spokesman for the AA said up to 18 million cars would be on the roads over the 24-hour period from Thursday night to Friday evening.
"There will be a delayed rush hour today," he said. "Rush hour won't start until 10am as people either go off to spend Christmas away from home or do Christmas shopping, so there will be a mixture of people travelling long and short distances."
Getaway traffic is likely to be heavy on major routes, including the M1 in Buckinghamshire and Bedfordshire, the M4 between London and Newbury in Berkshire, the M25 around London, and the M4 and M5 in the West Country.
The Highways Agency reported few problems. There are delays on the A27 westbound entry slip road from the A2030 near Portsmouth due to a lorry fire, and an accident has closed one lane of the A56 northbound in Lancashire.
It said 19 sets of roadworks and lane restrictions had been removed to ease congestion, and will not be put back until the new year.
A spokewoman for Gatwick Airport said Friday is expected to be its busiest day with 100,000 passengers travelling through. Of these 58,000 were departing the UK, with a total of 1.3 million passengers going through the airport during the Christmas period.
There were also big crowds at Heathrow Airport, with 35,000 flights scheduled to arrive at Terminal 5 alone.
Some train services were delayed, with disruption reported between Gloucester and Newport in South Wales due to signalling problems, and also between Liverpool Lime Street via Runcorn or Warrington.
