Drivers are being urged to avoid travelling on 'Frantic Friday' this week when the last of the year's commuter traffic will clash with the Christmas getaway.
Keiran Southern for MailOnline reports:
Leisure journeys will peak at 1.87 million on Christmas Eve, but December 22 is expected to see the worst delays as people driving home from work battle for road space with 1.25 million motorists visiting friends and family, according to RAC figures.
The worst hold-ups are expected to occur between 4pm and 8pm.
An estimated 11.5 million leisure trips will be made by car between December 17 and Christmas Eve, but this will be eclipsed by the 17.5 million between Christmas Day and New Year's Day as people take advantage of post-Christmas sales at shops.
Driving will cost more this winter as rising fuel prices mean filling up a typical family petrol or diesel car is around £3 more expensive compared with 2016.
RAC traffic spokesman Rod Dennis said: 'Things tend to get worse on the last working day before Christmas, with 'Frantic Friday' this year falling on December 22.
'We strongly urge drivers planning long journeys to avoid this day if they possibly can.'
Almost 400 miles of roadworks will be lifted by Highways England to ease journeys.
The 'roadworks embargo' will be in place on motorways and major A roads from 6am on Friday until 12.01am on January 2.
But the number of cars on the road could be even higher than normal due to a series of strikes by rail workers which threatens to reduce services on a number of days throughout the festive period.
Some 260 engineering projects on the railway will also disrupt journeys.
Many of Britain's mainline routes will be partially shut as Network Rail carries out its biggest ever Christmas investment programme.
Great Western Railway is urging passengers to complete journeys by Saturday 'at the latest' as London Paddington will be closed between Christmas Eve and December 27.
The West Coast main line will be halted between Preston and Lancaster from Christmas Eve to December 27, with buses replacing trains.
Passengers travelling between London and Glasgow during this time are advised to go via Edinburgh, adding around an hour to journeys.
Southeastern, which serves London, Kent and East Sussex, will not be able to run trains to London Bridge, Charing Cross and Cannon Street between Saturday and January 1.
Network Rail chief executive Mark Carne said: 'We know that our railway is up to 50% quieter than usual during the festive period so taking on and delivering these huge transformational schemes at this time of year minimises our impact on passengers.'
Coach operator National Express is running its largest ever Christmas schedule to meet increased demand from key locations such as Bournemouth, Cardiff, Leeds, Edinburgh, Portsmouth, Bristol, Glasgow and Manchester.
It is adding nearly 30,000 extra seats to services between Monday and January 2, with Christmas Day bookings up by almost a quarter on last year.
Whilst it’s important to spend Christmas with family and friends, perhaps it’s worth altering your plans to arrive a day before, making your journey on the Thursday instead to ensure a safer and less delayed journey.