UK motorists have been warned that some journeys could take four times longer in the lead-up to Christmas than at other times of the year.
Analysis of the last time Christmas Day fell on a Sunday, in 2011, led traffic information supplier Inrix to predict that 4pm on Friday (December 16) will be the busiest time on the roads during the festive period.
This is due to the combination of Christmas shoppers, leisure trips and people leaving work.
The most delayed routes are expected to be on major motorways.
The average speed in both directions on a 32-mile stretch of the M25 between Junctions 7 and 16 – which runs alongside Heathrow Airport – could fall to as low as 11mph, Inrix claimed.
This will extend journeys that typically take 35 minutes to nearly three hours.
Other routes set to be congested on Friday include the M5 southbound from Junction 14 to Junction 21 in the South West, both ways on the M6 between Junctions 16 and 22 in the North West and the M4 in both directions between Junctions 24 and 32 in South Wales.
December 27 has also been identified as a day when the roads could be jammed, with the volume of traffic rising due to high street sales, people visiting family and friends and those returning home for work on the following day.
Highways England, which manages England’s motorways and major A roads, said it will complete or lift 448 miles of roadworks by 6am on December 23 in a bid to ease the Christmas getaway.
Inrix traffic analyst Greg Hallsworth said: ‘There will be significant disruptions on the road due to the regular post-work peak, the start of the school holidays and people heading home for Christmas, as well as the number of delivery vehicles making their drop offs as e-commerce in the UK reaches a record high.
‘Drivers taking to the roads this Christmas would be well advised to take alternative routes or avoid driving during peak times altogether.’
AA president Edmund King urged shopping centres to provide more information on the lengths of queues leaving their car parks in the build-up to Christmas.
He called for better use of social media and electronic noticeboards to avoid shoppers spending hours stuck in hold ups.
Mr King said: “We would hope that shopping centres have contingency plans in place for when their car parks and the roads leading to and from them become gridlocked.
‘It is surely better that customers be told of delays and given the option to wait in the warmth of the shopping centre than for hours in their vehicles, moving forward a car length every quarter of an hour.
‘There should also be the ability to reduce or waive parking charges when shoppers are stuck through no fault of their own.’
According to research of traffic outside six shopping centres across Britain last year by the AA and Inrix, queues became as much as 600 per cent worse in the two weekdays after the schools broke up compared with other days running up to Christmas.
Shoppers driving out of Bluewater Shopping Centre in Kent were left stranded after heavy traffic blocked car park exits, with some customers reporting delays of up to six hours.
The rail network will also be disrupted over the festive period on a number of lines across the country as up to 200 improvement projects costing £103 million are carried out.
Passengers travelling in London, Manchester and Cardiff will be among the worst affected.
A strike by RMT conductors is also expected to cause disruption on the Southern network between December 31 and January 2.
Coach operator National Express is running its biggest ever Christmas service and has recorded a rise in bookings for December 25 up by more than a third compared with the same point last year.