With the school summer holidays starting this week, Britons are expected to jump into their cars en masse to enjoy the sun – despite rising petrol costs. Additionally, the extreme heat that has caused so much disruption and discomfort in recent days is expected to subside by the end of the week. The M25 could see some of the worst congestion as holidaymakers hit the roads in droves, along with problems on the A303 near Stonehenge, the M4 between Cardiff and Newport in south Wales and the M5 south of Bristol, according to the transport analysis firm Inrix. . Read more: Motorists hit by record monthly hike in petrol prices RAC spokesman Rod Dennis said: “The extreme heat affecting much of the UK in recent days may ease over the coming days, but we still expect the summer getaway to kick off in earnest as potentially record numbers of drivers head out on the roads this weekend – and that’s despite incredibly high fuel costs. “With school terms in England and Wales ending this week and millions of people ready for a break, we’re expecting a frantic Friday followed by a miserable weekend on major roads across the country, with traffic and congestion probably peaks on Saturday. “The advice to drivers embarking on a driving holiday is therefore clear – leave as early as you can in the morning or expect to sit in some long queues.” The research is based on a survey of 1,700 UK drivers.