Driving tired as hazardous as drink-driving

A sleep-deprived driver performed worse than a driver who was 25% over the legal limit, and almost as badly as a driver well over the limit, in tests conducted by What Car? magazine. Even allowing for a "snatched" four hours of sleep, the driving of the tired driver was "still dangerously" impaired, according to What Car?

In the tests, one driver was not allowed to sleep until 3am, while the other consumed 12 units of alcohol - the equivalent of 6 pints of medium strength beer, or slightly more than a bottle of wine - over the course of a night.

Using a driver simulator at the Transport Research Laboratory in Crowthorne, Berkshire, the two drivers negotiated routes which included motorways and A-roads.

When 25% over the legal limit, the drunk driver's ability to hold a steady distance from a car in front dropped by 25%, while his ability to keep to the centre of a lane dropped 23%.

At 2am, the sleep-deprived driver was 39% less able to maintain a steady distance from a car in front, and his capacity to drive within a lane suffered by 37%.

Don't drive tired'

The drink driver still proved to be the worse driver overall. When twice over the legal limit he was 49% worse at maintaining a steady distance and 42% worse at keeping to his lane.

His 'morning-after' results were also poor. After eight hours' sleep his skills were way below par. He was 26% worse at holding a steady distance from the car in front and 18% less able to keep a straight-line position, and he almost crashed.

What Car? group editor Steve Fowler said: "It's not surprising to learn that drink seriously affects driving ability, but it is worrying to discover that a sober person's driving ability can suffer more when they are tired.

"Our message to drivers is simple - don't drink and drive and don't drive tired. If you are feeling drowsy, pull over in a safe location, lock the doors and have a nap. It's better to arrive late than not at all."

Previous study

Almost half (40%) of What Car? readers admitted to falling asleep at the wheel in a recent survey, and 22% said it had happened more than once.

Tips offered to drivers by What Car? included planning for a good night's sleep prior to long journeys, and avoiding driving through the night.

It added that motorists should not be fooled into thinking that turning down the heating, opening the windows or playing loud music would help keep them awake. It said it was far more effective to stop, take a 20 minute nap and then drink some coffee, or another caffeine-based drink.

A separate study conducted by psychologist Dr David Lewis almost two years ago found that sleep-deprived drivers demonstrated behaviours similar to those of people who were over the legal drink-driving limit - see the link to our article from January '06 above/right.