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Dying for a nap?

By Kim O’Hare

Every year, police see “mystery crashes” in which it is not possible to determine a cause for a fatal car accident. Many of these incidents are thought to involve a fatigued driver who fell asleep at the wheel.

A typical mystery crash might occur on a highway when one vehicle drifts out of its lane into the path of oncoming traffic and hits another vehicle head-on, often with tragic results. If you fall into a microsleep and nod off at 100km/h, you’ll travel 100m in just four seconds - unconscious. pictureSomeone who has not slept for 18 hours is as impaired as someone with a 50mg blood alcohol level for which, in most jurisdictions, police can take away your driver’s license. 

Drivers suffering from lack of sleep can find it difficult to perform tasks such as driving that require coordination and mental alertness. Even losing a few hours of sleep can significantly affect drivers’ ability to judge or maintain speed, and to keep in the proper lane. Fatigue slows reaction time, impairs judgement and increases the risk of a collision.

Researchers say part of the problem is our busy lives. One recent survey revealed that 30 per cent of all respondents (45 per cent of those under age 30) said they cut down on sleep to fit more activities into a day. Other factors may include sleep problems related to sleep apnoea or shift work. The amount of time spent on the road, time of day and the use of medications or alcohol can also increase fatigue.

One new report suggests that driver fatigue could be the cause of almost one in five fatal car crashes. A spokesman for the Insurance Bureau of Canada points out that not taking a break could be a fatal decision, as driver fatigue kills about 400 Canadians every year. A 2005 study found one in five drivers admitting to falling asleep behind the wheel during the previous 12 months, and more than half admitted to driving while feeling drowsy.

In the UK, East Midlanders are the most responsible about taking breaks during long journeys, a poll by hotel company Premier Inn found. Of those drivers, 77 per cent said they have more than three breaks on long journeys.

The Selby train crash in 2001, in which ten people died, put the issue centre stage. Driver Gary Hart was jailed for five years for causing death by dangerous driving. A jury decided that Hart had fallen asleep at the wheel of his Land Rover before it plunged off the M62 into the path of an oncoming train. Kevin Clinton, head of road safety at Royal Society for the Prevention of Accidents, said: “The horrific crash at Selby illustrates just how catastrophic the consequences of driving when too tired can be.”

Telltale signs that you may be too tired to drive include loss of concentration, drowsiness, yawning, slow reactions, sore or tired eyes, boredom, feeling irritable and restless, missing road signs, difficulty in staying in the right lane, and nodding off. Shift workers and teenagers are especially susceptible. Drivers experiencing these symptoms are encouraged to pull safely over to the side of the road and stop for a nap.

Sleep Debt

Each of us has a specific daily sleep requirement. The average sleep requirement for college students is well over eight hours and the majority of students would fall within the range of this value plus or minus one hour. If this amount is not obtained, a sleep debt is created.

All lost sleep accumulates progressively as a larger and larger sleep indebtedness. Furthermore, your sleep debt does not go away or spontaneously decrease. The only way to reduce your individual sleep debt is by obtaining extra sleep over and above your daily requirement.

The powerful brain mechanism that regulates the daily amount of sleep is called the sleep homeostat. By increasing the tendency to fall asleep progressively in direct proportion to the increasing size of the sleep debt, this homeostatic process ensures that most people will get the amount of sleep they need, or close to it.

The elevated sleep tendency together with the associated drowsiness and an intense desire for sleep would ordinarily prevent most people from becoming dangerously sleep-deprived because they would go to bed early, or sleep late, when such excessive daytime sleepiness occurred.

However, in our society we are prone to ignore or resist nature’s signal that we need more sleep, and we often resist far too long. At this point, we cannot resist falling asleep. Depending on when and where this happens, falling asleep can be tragic, or merely inconvenient. As far as is currently known, nothing can change an individual’s fundamental daily sleep requirement. 

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