Driving With Fatigue Can Prove Fatal!!!

Fatigue is thought to be one of the biggest killers the world over, rivalling the effects of speed and alcohol. But the full extent of its role is not really known – unlike alcohol and drugs, fatigue can't be tested for in post-mortems. The effects of fatigue on driver performance have been documented in numerous studies in which subjects were required to perform driving tasks after long hours of wakefulness. Fatigue manifests itself in:

• slower reaction times: fatigue increases the time taken to react in an emergency;

• reduced vigilance: subjects perform worse on attention-based tasks when sleep-deprived. For example, a fatigued driver will be slower to notice oncoming hazards, such as roadworks or a railway crossing; and

• information processing: fatigue reduces both the ability to process information and the accuracy of short-term memory. Thus, a fatigued driver may not remember the previous few minutes of driving and will be slower in evaluating oncoming hazards.

The Centre for Sleep Research at Flinders University in South Australia has likened fatigue-induced impairments to those caused by alcohol: a person kept awake for 17 hours will perform at a standard comparable to that of someone with a blood-alcohol concentration (BAC) of 0.05 per cent (the legal limit in Australia). After 24 hours without sleep, a person will have capabilities similar to someone with a BAC of 0.10 per cent.

But probably the greatest hazard posed by fatigue is the risk of sleep itself. A fatigued driver who remains awake will probably be able to take some (perhaps belated) action to avert a crash, but one who has fallen asleep must rely solely on luck for survival.

Circadian rhythms

Researchers have long noted that fatigue-related accidents tend to occur in two distinct periods of the day – between midnight and 6 am, and between about 2 pm and 4 pm. These periods coincide with typical low-points in our daily pattern of alertness, or circadian rhythm (the word 'circadian' is derived from two Latin words: circa, meaning 'about', and dies, meaning 'day').

Most organisms follow a daily routine (circadian rhythm). Songbirds, for example, mark sunrise and sunset with their vocal-chords. Many Australian marsupials sleep during the day and go about their business in the relative cool of the night. Are these routines based purely on external factors? For example, do nocturnal animals simply get up when they notice that the sun has set, or is their behaviour also governed by some internal timing mechanism?

Scientists have shown that most organisms have internal 'clocks'. If the sun failed to rise one day, songbirds would still sing their usual tune. Plants whose leaves track the sun will continue to do so if kept in a perpetually dark room – as noted in 1729 by the French scientist d'Ortous de Mairan.

Scientists have gathered molecular evidence for an internal clock in humans, but circumstantial evidence is provided by the modern phenomenon of jet-lag. Travellers who have moved between time zones – say, from Australia to the United Kingdom (a difference of about 10 hours) – typically find it difficult to sleep, even when tired. It might be 10 pm in London and theoretically bedtime, but according to the body-clock it's 8 am and time to get up.

In humans, the circadian rhythm is controlled by a small region of the brain called the suprachiasmatic nucleus (SCN). The SCN is located in the hypothalamus, which regulates many functions of the autonomic nervous system.

One of the main ways in which the SCN transmits its time-related information is by stimulating the production of melatonin, a hormone manufactured in the pineal gland at the base of the brain. Melatonin levels typically increase in the body after sunset and reach their peak between 12 midnight and 6 am. This corresponds with the body's lowest levels of alertness and body temperature and its lowest capacity for the processing of incoming information. A second, smaller trough in these functions occurs in the afternoon, commonly between about 2 and 4 pm.

These two dips in the circadian rhythm are dangerous for drivers. Fatigue-related crashes are thought to be about twice as high at 2 pm as they are at 10 am, and nearly six times as high at 2 am.

Around 20% of fatal road accidents involve driver fatigue. In an experiment conducted in Victoria, Australia in 2007 about 30% of severe single vehicle crashes in rural areas involve the driver being fatigued. A Federal Government inquiry Beyond the Midnight Oil, Managing Fatigue in Transport, House of Representatives Standing Committee on Communications, Transport and the Arts, October 2000 into managing fatigue in transport reported fatigue related road accidents alone cost around $3 billion every year.

A study conducted by the Adelaide Centre for Sleep Research concluded that a person who has been awake for 17 hours faces the equivalent risk of having an accident as a person who has a BAC reading of 0.05 g/100ml, and is therefore twice as likely to have an accident as a person with a zero blood alcohol content who is not fatigued. Drivers who have been awake for 24 hours have an equivalent driving performance to a person who has a BAC of 0.1 g/100ml,and is seven times more likely to have an accidents.

Sleep Deprivation and Traffic Accidents

Sleep deprivation is often caused by sleep disorders that are unknown to the subjects themselves. A study at the Sleep Disorders and Research Center of Stanford University Medical School showed that truck drivers identified with sleep-disordered breathing had a two-fold higher accident rate than drivers without sleep-disordered breathing. Sleep disordered breathing, commonly known as sleep apnea, affects 15 million people in the United States. This condition, characterized by suffocation and oxygen deprivation, which wake the subjects up several times in the course of the night, is responsible for daytime sleepiness and fatigue

Perhaps an examination of the influence sleep deprivation has on our mental activity and performance level can shed light on how we can protect others and ourselves from the disastrous consequences of sleep fatigue. The influences of sleep deprivation on performance:

a) Slower reaction time: sleeplessness slows down your reflexes; reaction time slows down, preventing you from stopping in times of danger.

b) Decrease in concentration levels: When you are overly tired, your attention span decreases. Most people are subject to a decrease in attention every 90-120 minutes; however, sleepiness makes this decrease even worse and it can cause accidents when you fall asleep at the wheel.

c) Disorder in information processing: Sleepiness is very much like being under the influence of alcohol or drugs. When you are sleepy, your mental and psychomotor skills diminish. In one study, a group of subjects was kept awake for 28 hours; another group was given alcoholic drinks every half hour. When both groups were tested for hand-eye coordination, the ones who were sleep deprived performed equally bad as the ones with 0"5 blood alcohol level.