M4 through Berkshire set for 'significant delays' over Christmas
The AA says the M4 is likely to be among the most congested roads in the UK over the festive season
Nearly 18 million motorists are predicted to travel on roads in the lead-up to Christmas.
December 23 and Christmas Eve are looking to be the busiest days, with more than 17.8 million cars expected to travel on both days, while December 25 will be one of the quietest days on the road with more than 14.5 million motorists travelling, the AA has said.
December 18 is meanwhile predicted to be the busiest Saturday, with more than 16.5 million motorists heading out of the house to complete their Christmas shopping.
New Year's Day is predicted to be the quietest day on the roads over the festive period, with 8.9 million drivers out and about.
The AA's predictions have been made based on a survey of more than 15,000 drivers as well as Government data on the number of licenced cars on Britain's roads.
Of those who are driving, almost a third plan to do so for work on December 16 (31%) and December 17 (28%), after which business-based travel drops off until the new year.
Compared to previous years, it is believed that 2018 is the current record high, with the number of drivers on the road reaching more than 18 million.
A year later, the number of drivers over the festive period dropped to more than 17 million.
The AA has said there are expected to be delays to journey times on some stretches of motorway including the M25, the M5 between Bristol and Weston-Super-Mare and the M6 around Birmingham.
In addition, stretches of the M1 "smart" motorway from Luton northwards can often suffer congestion from incidents or breakdowns, as can the M62 and M60 in the North West.
Both the M4 and the M27 are also set to suffer from significant delays, the AA adds.
Edmund King, AA president, said: "It's a bumper-to-bumper Christmas this year as people want to make up for lost time. Providing there are no formal restrictions in travel or socialising, millions are ready to spend time with their friends and family.
"While December 23 and Christmas Eve look set to be the busiest travelling days, the change in working practices with increased home working, means we could see a spread of traffic across these days rather than a chaotic evening rush.
"Many breakdowns are preventable, so checking your vehicle before you set off is very important. Tyres, fuel, EV range and oil levels, coolant and screenwash checks should be made as a minimum. Likewise keeping water, high protein food or chocolate, warm clothes, coats and a hi-viz jacket will help keep you going should the worst happen."