Published as the holiday season starts, the study also shows that one in 10 (9%) drivers don't stop at all on long journeys unless they absolutely have to. Many also admit failing to get enough sleep the night before a long journey, as less than half (45%) make sure they get at least seven hours' sleep.

With driver tiredness being one of the biggest killers on our roads, Brake is advising drivers to take simple steps to avoid falling asleep at the wheel.

In 2011 in Great Britain it was reported 84 people were killed and 420 suffered serious injuries in tiredness related crashes although Brake says the real figure could be higher, because it can be difficult to prove when a crash is caused by a driver falling asleep. They tend to be high-speed crashes, because drivers do not brake before crashing, so the risk of death or serious injury is greater.

Action to tackle tired driving among fleet drivers is also needed because an estimated four in ten tired driver crashes involves a commercial vehicle driver.

Julie Townsend, deputy chief executive, Brake, the road safety charity, said: ‘A large proportion of the driving public are scarily confident they can push on through on long drives without stopping. In reality, regular breaks – at least every two hours – are essential for staying alert and awake, as is getting plenty of sleep the night before. Sleepiness can catch you unawares at the wheel and it only takes a couple of seconds on a motorway to cause absolute carnage.’

Brake recommends regular testing of people who drive for work for sleep apnoea, a treatable condition that makes falling asleep at the wheel much more likely, thought to be particularly widespread among HGV drivers. Brake also believes the rules controlling hours that can be driven by truck and bus drivers should be extended to cover fleet cars and vans.