Drivers are being warned over severe road congestion this weekend as nearly 13 million leisure trips are expected across the UK.
The RAC said it estimates 12.6 million people will embark on day trips or holidays by car between Friday and Monday, causing “bumper-to-bumper traffic”.
The majority of schools in England and Wales break up for summer on Friday.
That is set to be the worst day for congestion as holidaymakers compete for road space with commuters.
Transport analysis company Inrix predicted that traffic hotspots will include the M5 south from near Bristol (Junction 15) to Bridgwater (Junction 23), which is a popular route for holidaymakers travelling to the South West.
Another motorway stretch likely to experience hold-ups is the M25 clockwise between Junction 10 for the A3 to Kingston and Junction 6 for the A22 to East Grinstead.
Drivers wanting to avoid long queues are advised not to travel on major roads between late morning and early evening from Thursday to Sunday.
RAC spokesman Rod Dennis said: “There’s no doubting the UK remains an ever-popular holiday destination with millions of drivers expected to take to the roads at the end of this week as schools in England and Wales close for summer.
“With the West Country leading the pack when it comes to the most popular part of the country to visit, it means routes heading south and west are likely to encounter some of the longest queues.
“Anyone using the M5 southbound from Bristol should anticipate bumper-to-bumper traffic, with those travelling outside peak periods most likely to have a better journey.
“We’re seeing an enormous increase in breakdowns this year as drivers dependent on their vehicles for leisure and work contend with cripplingly high prices, leading to some scrimping on car maintenance as a result.
“It’s for this reason we’re urging drivers to take action to avoid a summer surge of breakdowns.
“No driver should set off before a long journey without carrying out a few basic checks to ensure their cars have got the right levels of oil and coolant, as well as making sure all tyres have plenty of tread and are properly inflated.”