Drivers are being warned to expect the busiest August bank holiday weekend on the roads since at least 2015.
The RAC estimated that 19.2 million leisure trips by car will be made between Friday and Monday.
The figure, based on a survey of 2,128 UK adults, is the highest since the motoring services company began recording data for the summer bank holiday in 2015.
The poll indicated that 84% of people who plan to travel by car for leisure this weekend will make a day trip.
One in 10 (10%) said they will set off for a holiday, while 6% will return from a holiday.
Saturday is expected to be the busiest day on the roads for leisure journeys, with 3.7 million planned.
This is ahead of Friday (3.2 million), Sunday (3.1 million) and Monday (3.0 million).
A further 6.2 million leisure trips are planned at some point over the four days.
Transport analytics company Inrix warned that the worst times for congestion are likely to be between 10am and 6pm on Friday, and between 10am and 1pm on Saturday.
Delays are expected on roads serving coastal resorts and on routes for Leeds and Reading music festivals.
Leeds Festival, which has been described as being the UK event that has the second biggest impact on traffic, is expected to cause long queues on the A1, A1(M), M1, M62 and A64 from Thursday.
It could cause journey times to be doubled at lunchtime on Friday along the A1 southbound between the Kirk Deighton and Bramham interchanges.
Roads in Kent will also be busy as many people head to Europe via the ports.
The Port of Dover expects to be used by more than 20,000 cars over the bank holiday period.
RAC spokesperson Alice Simpson said: “With the end of the school holidays fast approaching, it seems day trips will be the main cause of traffic this weekend.
“It is likely to be the busiest August bank holiday on the roads for nine years, so it’s important everyone ensures their vehicle is in good condition to avoid facing an unwanted breakdown.
“Whether you’re off to a festival, the coast or a theme park, or meeting up with friends and family elsewhere, the usual trusted advice applies: leave as early as you can to avoid the jams or be prepared to sit in some lengthy queues.”
National Highways national network manager Dale Hipkiss said: “We’re lifting more than 500 miles of roadworks to keep people moving this August bank holiday, and almost 97% of the network will be free from roadworks over the long weekend.
“We anticipate the roads will be busier than usual and are reminding people to check before they travel and leave plenty of extra time.”
Meanwhile, several major rail routes will be disrupted this weekend as Network Rail carries out engineering projects.
No long-distance services on the East Coast Main Line will run to or from London’s King’s Cross station from early evening on Saturday until early morning on Monday.
This will affect people travelling south returning home from the Edinburgh Fringe Festival.
A reduced timetable will be in place between Euston and Milton Keynes on Saturday and Sunday due to track renewals at Primrose Hill.
Services will also be disrupted in the Stoke area from Saturday until Tuesday, August 27.
An amended timetable will be in place between Euston and Manchester Piccadilly via Stafford, Crewe and Wilmslow.
Bus replacement services will also be in operation.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here