Road safety charity Brake and Direct Line today reveal more than half of drivers (55%) are ignoring basic advice to take rest breaks at least every two hours on long journeys, while one in 10 (9%) 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.
According to research by Loughborough University, after five hours' sleep you only have a one in 10 chance of staying fully awake on a lengthy journey.
The survey of 1,000 drivers from across the UK by Brake and Direct Line showed widespread complacency about the risks of tired drivers on long journeys. It found:
- Men are far more likely to drive for longer periods without stopping. 14% of men have driven for six hours or more without stopping, compared with 3% of women.
- Half of men (50%) have driven for four hours or more without stopping, compared with a third (31%) of women.
- A third of drivers (35%) admit sometimes or always trying to push on if they feel sleepy at the wheel. 38% of men do this compared to 31% of women.
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.
"The summer means long journeys for many families hoping to catch some sun at the coast or abroad. Brake is warning that to make sure you and your loved ones get there safely you need to allow plenty of time to take it easy, take regular rest breaks, and ensure you get a full night's sleep beforehand."
Rob Miles, head of motor at Direct Line, said: "Tiredness and driving are a deadly combination. Not only is there a risk of falling asleep at the wheel, but when we are tired our reactions and awareness of our surroundings are not as sharp as they would normally be.
"While tired drivers may think that stopping for a break will increase their journey time, it's not worth the risk to themselves, their passengers or other road users. It is better to get there late than not to arrive at all."