Cutting edge: Wake-up call for drivers approaching dead of night

February 21, 2003

Jim Horne has seen at first hand the tragic consequences of falling asleep at the wheel. He has some advice for both drivers and their passengers

The typical, tragic scenario involves a young man driving late at night, probably early Sunday morning, on a dull and monotonous road. He may well have played sport or undertaken other heavy exercise that afternoon. Any passengers will be fast asleep, somehow assuming that their driver could stay awake. He may have had one or two drinks earlier, but he will be well under the legal limit at the moment he falls asleep at the wheel. His car might run off the road and hit a tree, or bounce off the central reservation of a motorway, roll over and be struck by a truck or other vehicle. Falling asleep at the wheel is now recognised as one of the more likely causes of accidental death in young adults.

For one reason or another, most fall-asleep crashes involve male drivers, especially young men. They generally take more risks with most aspects of their driving - by overestimating their driving skills, believing themselves to be good at handling a vehicle at speed, or staying awake when driving tired. Although women drivers think more sensibly, they are no safer if they travel as a passenger with a confident but tired male driver.

Sleepiness affects the brain in subtle ways, for example, producing mild euphoria and impaired judgement of risk. This "buzz" of the small hours is why casinos open at night, as punters are more likely to feel lucky - and more likely to lose. It's another reason why driving without sleep in the small hours, when our "body clock" is also at its natural nadir, is the most likely time for these crashes.

Alcohol is a soporific, worsening any underlying sleepiness, which is why even small quantities, well under the legal limit, can have profound effects. It is why that single lunchtime drink can be so debilitating in the afternoon, when our body clock is having another, smaller dip.

Youth is accompanied by good and deeper sleep; hence young people's greater need for sleep and the worse the effect of sleep loss. Compared with oldies, young adults have a greater difficulty than they admit in staying awake, especially when driving on a monotonous road in the dead of night.

Physical fitness and exercise provide no protection against sleepiness, which, of course, is a state of the brain, not of the body. In fact, the feeling of relaxation following heavy exercise can simply aggravate underlying sleepiness.

For all drivers, young, old, men and women, these crashes are usually bad crashes - twice as likely as the average crash to end in death or serious injury, owing to the usually high impact speed without braking or swerving beforehand. At least one of these fatal crashes occurs each day in the UK.

I have seen the worst (as an expert witness) - the M40 minibus crash where 12 school children and their teacher died, the Selby rail crash with ten dead and more than 90 injured, as well as coach and truck crashes with multiple fatalities. They are not "accidents" but crashes due to preventable human error, even though the surviving drivers have little or no recollection of being sleepy or having fallen asleep - seemingly having had unforewarned "sleep attacks".

You have to be asleep for at least a minute to know you have been asleep. A driver who has "microsleeps" of only a few seconds will be unaware, but this is sufficient time for a crash. Nevertheless, sleep is always preceded by feelings of increasing drowsiness, to the point of "fighting sleep", when drivers will open the window, turn up the radio, push against the steering wheel, and so on. All useless acts, but by their very nature demonstrating to drivers that they are sleepy. Use these danger signs to stop driving.

At a meeting of the Parliamentary Advisory Council for Transport Safety on fatigue and transport accidents earlier this month, I described work that shows how sleepiness clouds one's memory and, for example, how few of us can remember how sleepy we were before bed-time last night or when it became noticeable. A straw poll of my audience revealed that no one could really remember back to the previous night. This forgetfulness is because the brain cannot be bothered to remember such pointless information. The same applies to hunger and thirst - we seldom remember either in any detail some hours after a meal or drink, even though it was clear at the time that we were hungry or thirsty. The point I am making is that it is not surprising that drivers who have fallen asleep at the wheel usually deny having felt sleepy. But it does not absolve them of responsibility for the crash, especially if they were driving when knowing that they had little sleep previously.

Finally, some survival tips. Taking that break? Have a strongly caffeinated drink followed by a brief snooze before the caffeine kicks in - do not waste time walking briskly around the service area, gulping fresh air, as is often and wrongly advocated. Are you a passenger? And have both you and your driver had a long, arduous day? And you are about to fall asleep? Be warned, your driver is not fit to drive.

Jim Horne runs the Sleep Research Centre at Loughborough University.

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