Motorists are being told to avoid major routes ahead of a Christmas getaway hell this weekend.
The RAC and transport analytics company Inrix said roads are likely to be busiest between 1pm and 7pm on those days.
Hotspots where queues are expected include the M3 between its junction with the M25 and the south coast, the M25 anticlockwise between its junctions with the M1 and the M23, and the M53 from Chester to Liverpool.
The RAC said it commissioned a survey of 2,100 UK adults which suggested 3.0 million leisure trips by car are planned for Friday, rising to 3.7 million for Saturday.
Getaway traffic is expected to peak on Christmas Eve, with 3.8 million journeys.
An estimated total of 29.3 million festive journeys will be made between Wednesday and Christmas Eve, which is the most since the RAC began recording the data in 2013.
A separate RAC poll of 1,074 adults indicted that 53% of people planning such journeys by car said they will use that form of transport because it gives them more flexibility and convenience.
More than a third (35%) said their journey would take too long via public transport, while 34% said public transport was not a practical option because they were travelling with several people or will have lots of luggage.
RAC spokesperson Alice Simpson said: "Our research suggests that with Christmas falling on a Wednesday this year, many drivers will be squeezing in their getaway trips right up until the big day itself.
"While the getaway starts to ramp up from Friday, snarl-up Saturday looks particularly challenging, as does Christmas Eve.
"Travelling outside peak hours might be the only way drivers miss the worst of the jams."
Inrix transportation analyst Bob Pishue said: "With so many people expected to hit the road this holiday season, drivers should expect delays in and around major cities.
"Planning ahead is key to avoiding the country's worst traffic jams."
National Highways said more than 95% of roadworks on its network of England's motorways and major A roads will be lifted from 6am on Friday and will not be reinstated until January 2.
This includes 45 miles of roadworks on the M1, which were put in place while additional emergency smart motorway stopping areas were installed.
National Highways customer service director Andrew Butterfield said: "With more people expected to travel during the festive period and recent storms causing widespread disruption, it's crucial for drivers to plan ahead and exercise extra caution on the roads.
"To help make journeys smoother, we're removing roadworks on 95% of the roads we manage."
National Highways uses the acronym Trip to remind drivers to: Top-up fuel, water and oil; Rest every two hours; Inspect tyres and lights; and Prepare by planning for severe weather.
Rail engineering work will lead to more pressure on the roads with several lines closed.
London Liverpool Street station will be closed from Christmas Day until January 2, and no trains will call at London Paddington between Friday December 27 and Sunday December 29.
There will be no direct services between Crewe and Liverpool – and a reduced service between Crewe and Manchester – from Saturday December 28 until Friday January 3.
Services in the Cambridge area will be disrupted between Friday December 27 and Sunday January 5, and no trains will run between Harpenden and London from Saturday December 21 to Sunday December 29.
There are also fears that staffing shortages at train operators will cause disruption.
