Asleep at the wheel

It’s late at night and you’re heading home at the end of a long day’s motorway drive. The car is comfortably warm, soothing music is playing on the radio and the road stretches endlessly, monotonously ahead. Gradually your eyelids grow heavier and your concentration begins to wane. You’re seconds away from becoming an accident statistic — one of the many motorists who have fallen asleep at the wheel of their car.

Fortunately, the vast majority of us will recognise the danger signs and take action before tragedy strikes, winding down a window to let in some fresh air and stopping for a break at the next available opportunity.

But not all drivers heed the warning signs. Some actually fall asleep behind the wheel, resulting in often horrific accidents. Crashes caused by a sleeping driver tend to be more severe than usual, precisely because the driver is unable to slow down or take avoiding action.

Until recently driver fatigue was not placed very high on the list of road safety priorities. Sleep related incidents are not recorded in UK accident statistics, and a major problem in determining the extent of the problem is that drivers who have fallen asleep at the wheel are likely to be reluctant to admit it — especially where an accident has resulted.

Dr Mervyn White, head of the Royal Surrey Hospital sleep study unit, says ‘We do have a problem because people are very sensitive about their driving. One of the questions we ask people who come to us with a sleeping problem is whether they have fallen asleep behind the wheel. Very few admit to it, but I suspect that many of them have done so and that’s precisely why they come to see us in the first place.’

However, there is growing evidence that driver fatigue plays a part in a significant proportion of road traffic accidents. Regional studies have indicated that drowsiness accounts for some 16% of all road accidents, and over 20% of motorway accidents. One study carried out on the M180 in South Humberside indicated that driver fatigue could have been implicated in all four of the fatalities that occurred on the road over a 12-month period, plus 47% of the serious injuries and 34% of the slight injuries.

Numerous factors contribute towards a driver feeling drowsy behind the wheel, explains Dr Peter Holden, the British Medical Association’s representative on the IAM Council. ‘It is an increasing problem because we travel in quieter and smoother cars, we try to cover greater distances, our eyes may be very tired from focusing on a computer screen all day long and increasingly we use aids such as cruise control that give us less to do at the wheel. While it’s true that a comfortable drive is less stressful, you actually need a minimum of stress to keep you awake.’

Business drivers are often particularly at risk because their companies expect too much of them, says Dr Holden. ‘Firms have got to stop expecting unrealistic schedules from their drivers, and drivers must have time to take regular breaks. By law an LGV driver isn’t allowed to put in more than four-and-a-half hours behind the wheel without a break, so why should firms expect more than that of their company car drivers?’

When on the road, drivers need to be particularly aware of the lulling sensation caused by regular patterns or noises, continues Dr Holden. ‘There is a problem of beat notes, particularly in automatic cars where there is a slight mismatch between engine speed and gearbox speed because of the torque converter. The RAF had this problem with the old multi-engined bombers they used during the war. They had to synchronise the engines to remove this beat because it was sending crews to sleep during a long flight. Music with a strong beat can act in the same way and be very soporific.’

Drivers must also be careful to avoid taking any medicines that cause drowsiness as a side-effect. Anti-motion sickness pills, sedative antihistamines and certain cold and flu remedies are among drugs available over the counter which can make driving dangerous. These carry a written warning so it is important to check the label of any drugs you are taking before getting behind the wheel.

It’s also important to be aware of the times when drowsiness is most likely to strike. Major disasters such as Three Mile Island, Chernobyl, Bhopal, and the sinking of the Herald of Free Enterprise and Exxon Valdez, all occurred during the early hours of the morning when the body’s natural rhythms are at a low ebb.

Professor Jim Horne, Director of Loughborough University’s sleep research laboratory, comments that ‘The effect of the time of day of driving in relation to the body’s natural biological clock is profound, and is at least of equal importance as the duration of the drive. Young drivers are the most likely to have these [fatigue related] accidents, especially in the early morning, whereas older adults may be more vulnerable in the early afternoon.’

Studies carried out by Professor Horne have confirmed a surge in sleep-related accidents at these times. He notes ‘low incidences of sleep-related vehicle accidents during 0900 – 1059hr and 1900 – 2059hr which are times of the day when people naturally feel more alert. The peak times for all road accidents in the UK are around the rush hours of 0800 – 0900hr and 1700 – 1800hr, which are distinct from the peaks associated with sleep-related vehicle accidents.’

One category of drivers who may particularly risk feeling drowsy behind the wheel are those who suffer from a disorder such as sleep apnoea. This may be more prevalent than was once thought. ‘Sleep apnoea is generally said to affect 8% of the population,’ says Dr Mervyn White, ‘but personally I would say that 25% to 33% of the population after the age of 40, male and female, have some sort of obstructive airway problem.’

‘The disorder is caused by the pharynx at the back of the throat, which in some people flops back and blocks the airway once they have gone to sleep. The oxygen concentration in their blood goes down, and when their brain senses this it sends them a message to wake up. As they do so they regain control of their pharyngeal muscle and so clear the blockage. They don’t wake up fully but drift off to sleep again, and then the cycle repeats itself over and over throughout the night. So although they apparently have had a good night’s sleep, they wake up in the morning un-refreshed and go through life feeling constantly tired.’

Excessive snoring is often the first sign of sleep apnoea, particularly if the person still snores while sleeping on their side. If untreated the condition can lead to heart and lung problems, as well as the dangers a sufferer faces in everyday life while driving or operating dangerous machinery. Treatment involves sleeping with a CPAP (continuous positive airway pressure machine) worn over the nose. This provides a steady pressure of air into the lungs, pushing the soft tissue of the pharynx out of the way to maintain a clear air passage and give the patient an untroubled night’s sleep.

In August last year, sleep apnoea was used for the first time as a mitigating factor in a motoring court case, with a Derbyshire lorry driver being given a suspended sentence after falling asleep at the wheel and driving into a queue of motorway traffic, killing two people. However, the more general excuse of falling asleep at the wheel is not so likely to be accepted by magistrates. Legal precedents have established that a driver who falls asleep is committing at least the offence of driving without due care and attention. It could also come under the more serious offences of dangerous driving or causing death by dangerous driving. But convictions are unlikely to result in the absence of additional factors such as driving under the influence of drink or drugs.

Crucially, the onus is on the driver to take steps to avoid falling asleep behind the wheel. ‘Drivers falling asleep are unlikely to recollect having done so,’ says Professor Horne, ‘but they are aware of the precursor of feeling sleepy, as normal sleep does not occur spontaneously without warning.’

‘Putative countermeasures to sleepiness during continued driving, such as cold air, or using the car radio, offer only temporary relief at best. The only safe countermeasure is to stop driving. Then, a short nap and/or cups of coffee can be very effective. Exercise is of little use. More driver education is needed about the dangers of driving whilst sleepy.’ Dr Rob Tunbridge, road safety research programme manager at the Department of Transport, also emphasises drivers’ responsibility to take note of the warning signs of drowsiness.

‘In experimental studies drivers are invariably aware of how sleepy they are. They do not suddenly fall off to sleep or go into a trance-like state. They do however have a pronounced tendency to continue driving even when very tired. The implications of this are that although devices such as rumble strips can be very effective in warning drivers in the early stages of sleepiness, they will not eliminate the chances of having an accident if the person continues to drive. This makes it of paramount importance to emphasise to drivers the need to adopt measures which will minimise their chances of becoming sleepy.’

Recent research carried out by Professor Horne suggests that combining the nap and the coffee can be the most effective step of all. Caffeine in coffee takes half an hour to have an alerting affect, so it’s possible to have a short nap after drinking a cup, and his study showed that this ‘combined treatment’ effectively eliminated the mid-afternoon peak of sleepiness while behind the wheel.

Ultimately, drivers must recognise the dangers of continuing to drive while they are tired and have the self discipline to stop and take a break instead of pressing on, even if they are running late.

‘I often face a 200 mile drive at 11 o’clock at night,’ says the IAM’s Dr Holden. ‘I’ll crack the first 50 miles then pull in and go to sleep for half an hour – it’s a sight better to add half an hour to your journey than spend three days in intensive care.’