People driving home for Christmas, or anywhere, are being urged not to travel on major routes for six hours this weekend.
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.
The RAC and transport analytics company Inrix said roads are likely to be busiest between 1pm and 7pm on those days.
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.”
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.”