This Easter is set to be one of the busiest on the roads "for several years", the AA said today.
Around 10 million cars are set to take to the roads over the Easter holiday, according to AA Roadwatch and traffic information company Trafficmaster.
And a further eight million cars will be on the move over the royal wedding weekend at the end of the month, the two organisations forecast.
Trafficmaster said the congestion hotspots were likely to include:
:: The M5, A303, A30 and A38 in the West Country;
:: The M3 around Winchester in Hampshire and the A21 through Sussex;
:: Roads leading to the Channel Tunnel and the Channel ports;
:: The M11 to Stansted Airport in Essex and the A12 to the East Anglia coast;
:: The M1 in the East Midlands and South Yorkshire, as well as the M6 in the West Midlands, Lancashire and the Lake District;
:: The M56 and the A55 between Manchester, Chester and along the North Wales coast:
:: The M90, A90 and Forth Road Bridge between Edinburgh, Fife and Tayside in Scotland.
An AA/Populus survey of around 13,000 AA members showed that 85% were planning to stay in the UK over the Easter and royal wedding bank holiday periods.
A third are planning to make car trips over Easter, with those in Northern Ireland the most likely to take to the road, while the Scots are the likeliest to stay at home.
AA patrolman of the year Paul Leather said: "Our research shows that Easter will be the busier of the two bank holiday weekends, as the schools are still out.
"We expect congestion to peak on Maundy Thursday April 21."
Trafficmaster said that as Easter falls at the end of the school holidays, there would be more of a staggered getaway.
The main getaway is expected to start in earnest this weekend as people will only have to take four days off to get an extended break.
This Friday (April 15) is expected to see a busier evening rush hour as people head off early, with traffic remaining heavy over the weekend, especially in London and south east England, with FA Cup semi-finals at Wembley and the Virgin London Marathon on Sunday.
By Easter, the Highways Agency will have completed a number of works on England's motorways and major A roads and will be suspending 144 miles of work at other sites.
The suspension will be from 6am on Thursday April 21 until midnight on Monday May 2.
But works will remain in place at 22 locations, including a section of the M25 near St Albans in Hertfordshire and the M1 near Luton in Bedfordshire.
The RAC warned that roads around theme parks, shopping centres and retail outlets were likely to be busy over Easter.
RAC patrol ambassador of the year, Kevin Andrews, said: "People need to plan their journeys before setting off.
"Allow plenty of time for your journey particularly if you're heading for a popular resort or travelling at peak times."
British Transport Police (BTP) said some of its officers would be travelling down from north west England on trains carrying fans of Manchester United and Manchester City who contest the first of the two FA Cup semi-finals at Wembley on Saturday.
BTP said there would be an alcohol ban on trains travelling to and from the match.
Superintendent Dave Roney, of BTP, said: "Throughout the day we will have officers patrolling stations and on-board trains between Manchester and London. We will not tolerate intimidating or anti-social behaviour from those intent on spoiling the day for others."