MORE than half of motorists habitually drive for longer than two hours on motorway journeys without taking a break.

And 25 per cent of all drivers never stop for a rest during motorway journeys lasting four hours or longer.

These are the findings of a nationwide survey undertaken by the Institute of Advanced Motorists (IAM) and Auto Express magazine as part of National Motorway Month.

The survey, conducted by NOP World Automotive, also showed a third of drivers admit to having driven continuously for four hours or more without a rest on at least one occasion.

Company car drivers generally continue for longer periods without a break than drivers of privately owned vehicles, while female drivers tend to stop more frequently than their male counterparts.

When it comes to age, drivers in the 25-34 age group are the worst offenders.

The results show many drivers are either unaware of or ignoring official advice from the Department for Transport to take a 15-minute break every two hours on a long journey. The DfT says more than one-fifth of motorway collisions are caused by drivers falling asleep at the wheel and up to one in ten crashes on all of Britain's roads – around 23,000 a year – are also linked to fatigue.

The IAM’s chief examiner, Bryan Lunn, said: “Driver fatigue can easily set in on a long motorway journey, even if the driver begins the journey feeling fresh and alert. The problem can be particularly acute during the summer, when holiday traffic is at its peak and people are eager to reach distant destinations as soon as possible.”

The IAM offers these tips to reduce the effects of tiredness on a long motorway journey:

1) Plan in advance so you can stop for a 15-minute break every two hours.

2) Try to avoid making long trips between midnight and 6am, when natural alertness is low.

3) Never start a journey if you are already feeling tired.

4) If you start to feel sleepy, find a safe place to stop (not on the hard shoulder), take a short nap and resume your journey 15-20 minutes later. If necessary, drink strong coffee or a high-energy drink or take a caffeine tablet before setting off again.

5) Do not rely on opening the window or turning up the radio because these will do little to stop you falling asleep at the wheel.