Drivers are being warned to expect delays on what is predicted to be the busiest day for road travel of the Easter weekend.
The RAC estimates around 4.62 million journeys by car are likely across the UK on Good Friday.
It is predicting a total of 21.46 million trips over the bank holiday - the highest figure since 2014.
The motoring group said disruption to trains due to engineering works could also push more people onto the roads.
Rod Dennis from the RAC advised drivers to set off early, with roads forecast to get busier towards the middle of the day.
"Expect your journey, especially if you're going any distance, to take longer than it normally would," he told the BBC's Today programme.
After two years of relatively quiet Easter bank holidays on the roads due to Covid restrictions, Mr Dennis said: "It's very possible this weekend could turn out to be one of the busiest for leisure journeys for many years".
Data from transport analytics specialists INRIX suggests the M6 north between Liverpool and the Lake District, south towards Stoke-on-Trent, the M25 between Surrey and the M40 exit, and the A303 near Stonehenge could see some of the worst congestion.
Meanwhile, rail passengers are facing delays and cancellations, with Network Rail carrying out 530 engineering projects across the bank holiday weekend, costing a total of £83m.
No trains will run in or out of Euston station in London until the end of Monday on the West Coast main line, which is likely to disrupt football fans going to the FA Cup semi-finals at Wembley.
Trains to the West Midlands, north west England and parts of Scotland will instead start from Milton Keynes Central.
There will be also be no Southern services to and from London Victoria all weekend, nor any direct trains from London to Stansted Airport.
Alternative services are expected to be busy and Network Rail has advised people to travel either side of the bank holiday.
Disruption is also continuing at the Port of Dover, where P&O Ferries' services are still not running.
There were long queues at the port on Friday morning, with some travellers complaining they missed their ferries after waiting for hours.
Ferry company DFDS initially advised customers on Friday morning to arrive at least 90 minutes before their departure time, saying it was "expecting a busy day through the Port of Dover".
However, it later updated its guidance, urging customers to allow two hours.
It said customers delayed due to traffic at border control would be transferred to the first available departure.
Some lorries are being forced to queue on the A20 outside Dover, as part of the Traffic Access Protocol (TAP) scheme, which is designed to limit congestion in the town.
P&O Ferries' Dover-Calais services remain suspended, nearly a month after the company sacked around 800 workers without notice.
Two of the company's ferries which normally serve the route are still detained after they failed safety inspections.
Bad weather, the Easter holidays and problems with an IT system for customs checks following Brexit have also contributed to congestion around Dover in recent days.
This has led to long queues for lorries crossing the Channel.
Operation Brock, where lorries heading to Dover queue on one side of the M20, was put in place last week to help manage the traffic.
However, National Highways said it had now been scaled back as the threat of disruption had reduced.
Richard Ballantyne, chief executive of the British Ports Association, said the queues around Dover had now eased.
"In terms of the Easter getaway, it was worse two weekends ago and last weekend," he told the BBC.
Mr Ballantyne said the decision by DFDS last weekend to say it could no longer accommodate P&O ticket-holders, whilst frustrating for customers, had "kept a chunk of people away".
Meanwhile, there were long queues for Eurostar services at London's St Pancras station on Friday.
Airports are also expected to be busy, with many people taking the opportunity to head abroad for the first time since Covid travel restrictions were lifted.
More than 9,000 flights are scheduled to depart from UK airports between Good Friday and Easter Monday, according to aviation data firm Cirium.
The figure is 78% of the total for the same period in pre-pandemic 2019.
Cirium said the busiest day will be Good Friday, when around 2,430 flights are due to depart.
Some travellers have faced long queues at airports and cancelled flights over the Easter holidays, with staff shortages and Covid-related absences blamed for the disruption.
The travel industry cut thousands of jobs during the pandemic, but as demand for flights has returned, it has struggled to recruit, carry out security checks and train new staff quickly enough.
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