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The new personal Tiredness Warning System has many applications including the freight, transport, shift workers and aviation industries to name a few.
Employers and operators show are demonstrating a proactive risk management and training program have potential to negotiate low workers compensation and motor vehicle insurance premiums.
A TWS should only be used as a backup device and never solely relied upon. There is no substitute for training and common sense. |
"Fatigue is the silent killer on the roads and could be responsible for up to 30 per cent of deaths and a bigger percentage of serious injury crashes leaving many people in wheelchairs or worse for the rest of their lives. shift workers, people who work long days, students and those socialising into the early hours of the morning and those not getting enough sleep can easily tune out for a fatal few seconds.' Office of Road Safety.
Truck driver fatigue can severely impair the judgment of an individual who is behind the wheel of a commercial motor vehicle. It is particularly dangerous because one symptom includes the decreased ability to judge their own level of tiredness. Other symptoms vary between drivers, but may include;
A recent 4 year study in the USA has shown that most drivers who were involved in fatal fatigue-related accidents were males. During the 4 year span of the study, 82% of fatal fatigue-related accidents involved men.
Inquest hears about high number of fatigue-related road crashes.
Many of the millions of passengers have traveled for hours, crossed time zones and missed sleep. Often suffering from jetlag, many then decide to push their brains and bodies to the limit. They drive home from the airport. Inside Out looks at jetlag and its role in tragic road accidents. Jetlag explainedJetlag occurs when you travel rapidly through time zones. Your body’s biological clock can become ‘desynchronised’ and this may affect physical and mental performance. Here are some symptoms of jetlag ..
Dangerous drivingInside Out’s research at Manchester Airport found that 50 per cent of transcontinental passengers were driving home. They are undeterred by the fact that a fifth of all accidents on Britain’s motorways are believed to be fatigue related. North Yorkshire police believe a significant percentage of those are down to people coming off flights. Traffic Constable Brian Rogers from North Yorkshire Police has attended tragic accidents where holiday luggage has been strewn across the carriageway. He says, "People go on holiday to enjoy themselves and the memories are just of misery." Avoiding accidentsIf you are experiencing symptoms of jetlag, the safest decision is not to drive. Here are some tips to avoid the symptoms developing ..
Tragic experience
Source: Inside Out - Yorkshire & Lincolnshire: Monday 14th October, 2002
Fatigue and fatigue research: The Australian experienceDr Narelle Haworth
Paper presented to 7th Biennial Australasian Traffic Education Conference, Speed, Alcohol, Fatigue, Effects, Brisbane, February 1998.
ABSTRACT
This paper reviews the extent and nature of fatigue in road crashes in Australia. It then summarises the research that has been undertaken in that area and the issues that have arisen. Countermeasures to reduce fatigue are discussed, along with constraints to their effective implementation.
INTRODUCTION
In recent years there has been much interest in the role of driver impairment in the causation of road crashes. The identification of the role of alcohol in driver impairment and the consequent actions taken to reduce its incidence have played a large part in the reduction in road injuries and fatalities that has occurred in the past decade. An understanding of the role of driver fatigue has potential to lead to further improvements in road safety.
WHAT IS DRIVER FATIGUE?
The problems in specifying an adequate definition of fatigue have been well documented (see Cameron, 1973). However, most definitions include the concept of a deterioration with extended effort in work output, physiological well-being or feelings (Haworth, Triggs and Grey, 1988).
A simple model of driver fatigue was proposed by Hattori, Matsuura, Narumiya, Araki and Ohnaka (1987), who demonstrated three stages of driver performance in extended driving. The driver began in Stage One, characterised by alertness. In Stage Two (drowsy driving) drivers appeared to be sleepy, and "had a tendency to decrease their close attention to safety and to drive gazing vacantly at one unspecified point" (p.249.4). The car speed was kept fairly constant but there was often a delay changing speed in response to change of gradients of the road. This type of driving has been referred to as highway hypnosis (Williams, 1963).
Hattori et. al. (1987) report that in Stage Three (dim driving) "the consciousness level of the driver seemed to become even lower and blinkings were extremely reduced. The steering operation became more dilatory than in stage two and the zigzag driving within the permitted lane became pronounced. During this repeated zigzag driving the car sometimes crossed the centre line or ran off the side of the road" (p.249.4). In Stage Three a high level of fatigue is present and vehicle control is difficult to maintain.
The most dangerous aspect of driver fatigue is falling asleep at the wheel. While drivers affected by fatigue may have slower reactions and impaired visual scanning, they may be able to compensate to some extent for these impairments by, for example, slowing down or being less willing to overtake (Brown, Tickner and Simmonds, 1970). Näätänen and Summala (1978) conclude that "research has not generally been able to show that driver fatigue increases the risk of an accident except by increasing the probability of falling asleep during driving" (pp.27-28).
THE EXTENT AND NATURE OF FATIGUE IN ROAD CRASHES IN AUSTRALIA
An overall estimate of the proportion of accidents in which fatigue is involved is difficult to make and is likely to be misleading. The contribution of fatigue is greater in night-time accidents and in accidents occurring in rural areas. Because rural speeds are generally high and because sleeping drivers do not take evasive action, fatigue-related accidents are often severe.
Fatigue-related accidents are more common on rural highways than on urban roads. One reason for this is that average trip lengths are likely to be longer on these roads and inattention and drowsiness are brought on by the constant speeds and monotony. In addition, on such highways many other causes of accidents - poor access control, presence of unprotected utility poles, sub-standard road geometry, etc. - have been removed.
Identification of crashes as fatigue-related can be difficult. Coronial and police citations of fatigue occur in about 5% of all fatal crashes (Haworth and Rechnitzer, 1993), with percentages up to 14% in less populated states. Analysis of the same database for 1988, 1990 and 1992 showed that fatigue was involved in 5 to 10% of fatal semi-trailer crashes (Hartley, Arnold, Penna, Hochstadt, Corry and Feyer, 1996). However, these figures are based on very strict definitions of fatigue. Including crashes in which loss of concentration may have contributed to the crash increased the prevalence of fatigue in NSW crashes to about 17% (NSW Roads and Traffic Authority, 1993, 1994, cited in Hartley et al., 1996). Ryan, Wright, Hinrichs and McLean (1988) carried out an in-depth study of crashes on rural roads near Adelaide. When all accident-involved drivers were asked, 31.4% responded that they had felt slightly, moderately or very fatigued just prior to the accident. The percentage reporting fatigue was higher for truck drivers (41.7%) and motorcycle riders (50.0%).
Many night-time rural accidents are single-vehicle accidents. Johnson (1980, cited in Chapman, 1985) studied night-time rural accidents in South Australia. In this study 71 per cent of accidents were found to be single-vehicle accidents. Of the single-vehicle accidents, Johnson found that 92 per cent were run-off-road accidents. These accidents mainly occurred either on curves or involved hitting roadside objects (usually trees). A study of rural single-vehicle accidents in Victoria concluded that it was probable that the driver had fallen asleep in 27% of the crashes investigated (Armour, Carter, Cinquegrana and Griffith, 1988).
Driver fatigue in truck accidents
International evidence has accumulated which suggests that fatigue may be a significant contributor to truck crashes. Transportation Research and Marketing (1985) concluded that fatigue was a primary cause in 41% of heavy truck crashes in the western United States and a probable cause in a further 18%. Jones and Stein (1987) conducted a study in Washington State which found that the crash risk for drivers of articulated vehicles who had driven for more than eight hours was double that of drivers who had driven for less than eight hours. To put this in perspective, this means that someone who has driven for more than eight hours is operating at a similar risk to someone who has a BAC of .05.
The magnitude of the contribution of fatigue to truck crashes in Australia has become clearer in the last few years. In a NSW study, Fell (1987) reported that "articulated trucks have a high involvement in fatigue accidents in comparison with their involvement in other accidents" (p.60). Articulated trucks in NSW were found to have 3.7% of all fatigue-related accidents but only 1.5% of all non-fatigue-related accidents.
Leggett (1988) examined the contribution of fatigue to both car and truck crashes in Tasmania. He found that the contribution of fatigue increased with crash severity, mainly because of the often fatal nature of single-vehicle run-off-road crashes. Analysis of all reported crashes showed a slightly lower involvement of fatigue in rural single-vehicle truck than car crashes. When property damage crashes were removed from this sample, however, fatigue was shown to contribute more to truck than car crashes. Another important finding was that the likelihood of the truck driver being killed was greater in fatigue-related crashes than in other crashes.
A study of driver fatigue in fatal accidents involving a truck in Victoria was undertaken by the author and her colleagues (Haworth, Heffernan and Horne, 1989). Based on Coroners' verdicts, fatigue was a contributing factor in 9.1% of crashes. This figure is likely to be an underestimate because Coroners rarely judged fatigue to be a contributing factor unless there was strong evidence that the driver was likely to have been asleep at the time of the crash.
An alternative estimate of the contribution of fatigue was calculated by classifying as fatigue-related those crashes which involved several of the factors: extended driving hours, evidence of falling asleep at the wheel, comments about tiredness, driving right of centre in the absence of elevated BAC and night-time driving. This resulted in a judgement that fatigue was involved in 19.9% of the sample of fatal crashes involving trucks.
One of the interesting findings from the examination of Coroners' reports was that the car drivers involved in the fatal truck crashes were just as likely (or more likely) to have been fatigued as the truck drivers.
DRIVER FATIGUE RESEARCH
Driver fatigue research in the past can be classified into investigations of:
The epidemiology of fatigue
In Australia, several large surveys have been conducted to describe the extent and nature of the experience of fatigue among car (Fell, 1995; Fell & Black, 1996) and truck drivers (Hartley et al., 1996; Haworth, Vulcan, Schulze and Foddy, 1991; Williamson, Feyer, Coumarelos and Jenkins, 1992).
About one-quarter of car drivers reported having had a fatigue-related incident and 4% reported having had a fatigue-related accident in a NSW survey conducted by Fell (1995). Fell and Black (1996) found that 12% of Sydney drivers reported having a fatigue related incident. About a third of these had commenced the trip in a fatigued condition.
The surveys of truck drivers found that fatigue is a common problem. Williamson et al. (1992) reported that most truck drivers considered fatigue to be a substantial problem for the road transport industry and one third of drivers reported it as a substantial personal problem. Haworth et al. (1991) found that almost half the drivers reported that they drive on the edge of falling asleep at least sometimes. Hartley et al. (1996) reported that truck drivers in Western Australia perceived fatigue as less of a problem than drivers in other states.
Measures of fatigue
Measures of fatigue generally fall into those which are measured before and after the task and those that are measured during the task. Before and after measures include:
Factors contributing to the development of driver fatigue
The earliest view of driver fatigue was that it was directly related to the number of hours spent driving. Since then a large number of factors have been demonstrated to affect the development of fatigue. Figure 1 shows an early schematic representation of the variety of factors contributing to fatigue and the build up of chronic fatigue if recovery time is insufficient.
Figure 1. Schematic representation of the cumulative effect of daily causes of fatigue (from Grandjean, 1968). Fatigue is compared to the level of liquid in a container, and recovery is shown as the outflow from the container.
Time of day is probably the strongest factor affecting the development of driver fatigue. This was confirmed by the Driver Fatigue and Alertness Study (Wylie, Shultz, Miller, Mitler and Mackie, 1996) which compared driver performance on 10 and 13 hour workdays. The study showed that number of hours or days of driving were not strong or consistent predictors of driver fatigue.
Detailed discussions of the factors contributing to driver fatigue can be found in Haworth (1995) and Haworth, Triggs and Grey (1988).
COUNTERMEASURES TO REDUCE FATIGUE
A large number of measures have been proposed or implemented with the aim of reducing death and injury from fatigue-related crashes. These measures are classified in Table 1, according to their aim and whether they target the driver, vehicle or environment. Fatigue countermeasures can have three aims:
• To prevent fatigue by maintaining driver alertness • To prevent fatigued drivers crashing by providing a warning • To reduce the severity of fatigue-related crashes.
A classification of fatigue countermeasures (from Haworth, 1990).
The most widely implemented of these countermeasures have been education, limitation of hours of work, rest breaks, fatigue monitors and pavement treatments.
Educational programs
Educational programs to reduce driver fatigue and the constraints to their success are discussed by Haworth (1996). Some of the specific goals of fatigue educational programs are:
Traditionally, educational programs have been most successful at informing people and least successful in changing behaviour (unless they have been undertaken in support of an enforcement program, Cameron, Haworth, Oxley, Newstead and Le, 1993).
Two methods of educating drivers about the dangers of fatigue and ways of reducing fatigue have been used: media campaigns and incorporation of fatigue education in driver training courses. In general, fatigue advertising has been concentrated in the periods leading up to Christmas and Easter holidays. In New South Wales and Queensland particularly, advertising has focussed on providing support for volunteer-operated rest area refreshment break programs (Driver Reviver, Operation Coffee Break).
A Fatigue Management Training Course has been developed for the National Road Transport Commission (National Road Transport Commission, 1996) as part of a Transitional Fatigue Management Scheme. The purpose of the course is
The two major factors affecting the likelihood of success of educational programs to reduce fatigue are the ability of fatigued drivers to judge the level of risk at which they are operating and the incentives to continue driving.
Wertheim (1978) proposed that drivers be taught to recognise the early signs of fatigue such as misjudgment of velocities, crossing marked lane lines, slow responses and yawning. Once these events occur drivers should rest. However, experimental evidence suggests that subjective estimates of fatigue may not be reliable (e.g., Yabuta, Iizuka, Yanagishima, Kataoka and Seno, 1985). This agrees with the intuitive reasoning that if drivers knew that they were about to fall asleep at the wheel, that they would stop and so avoid crashing.
The effectiveness of attempts to persuade drivers to take rest breaks (including educational attempts) is limited by the real incentives to continue driving. These incentives are particularly strong for truck and bus drivers who have a need to meet schedules. For car drivers, time is also sometimes a factor.
Among young male car drivers, there is something of a machismo element that says that it is a sign of weakness to need to stop. Another widely reported disincentive to stopping for both car and truck drivers is the lack of attractive and practical places to stop. While rest areas exist, they are often not attractive at the time of day when needed most. Very few rest areas have adequate lighting and personal security.
In addition to these factors, Haworth (1996) discusses a number of more general advertising factors which may affect the success of fatigue educational programs.
There have been few evaluations of whether fatigue educational programs actually change behaviour and thus prevent fatigue-related crashes. However, the evaluations which have been conducted suggest that fatigue advertising seems to reach and be recalled by the target audiences. Thus advertising may be successful in informing drivers about the dangers of fatigue. The ultimate benefit of increasing the level of public awareness of fatigue as a road safety issue may be in making more acceptable the possible future introduction of technological or legislative measures which will be effective in reducing fatigue-related crashes (Haworth, 1996).
Limitation of hours of work
Most developed countries have regulations which limit driving hours for drivers of heavy vehicles. The regulations commonly include a limitation on the maximum number of hours that can be driven per day or per week and specifications relating to the length and timing of rest periods. Some jurisdictions limit driving hours (that is, hours behind the wheel) whereas others limit working hours (which may include loading, paperwork, waiting etc.). The underlying assumption is that limiting the hours of driving per day and per session results in drivers who are more alert and are, therefore, involved in fewer crashes.
The current driving hours regulations were framed at a time when little was known about the causes of fatigue and so they do not take into consideration many of the factors that are now known to be important. Feyer and Williamson (1995) note that current driving hours regulations have three critical shortcomings: they place limits on consecutive hours of work and rest irrespective of the time of day, they are not derived from empirical research basis and do not take into account inter- and intra-driver variability. "The omission of important factors affecting alertness levels, such as time of day, activity during rest breaks and prior activity, means that these regulations are incapable of being completely effective, even if problems related to enforcement were solved" (Haworth, 1995, p.46).
While improving safety by reducing fatigue-related crashes has been a major aim of the regulation of driving hours, the ability of these regulations to achieve this aim has been questioned in the last decade (Haworth, 1998). In addition, the development of alternatives to driving hours regulations - driver alertness monitoring or fatigue management programs - have led to an increasing debate about the usefulness in both safety and productivity terms of driving hours regulations.
Rest breaks
Advance planning of trips and scheduled rest breaks have been advocated as measures which can be taken by car drivers to minimise the development of driver fatigue and reduce the risk of crashing as a result of falling asleep at the wheel. However, the effectiveness of rest breaks has been shown to depend on a number of factors.
Rest breaks may not be helpful once a considerable level of fatigue has developed (Harris and Mackie, 1977; Lisper and Eriksson, 1978, cited in Lisper, Laurell and van Loon, 1986). Lisper and Eriksson (1977, cited in Lisper and Eriksson, 1980) investigated the effect on truck drivers of a 30 minute break between a 6 and a 5 hour session. They found that breaks were less effective at night than during the day and were more effective for younger than older drivers.
Studies of the minimum length of an effective rest break have been conducted in the laboratory and on the road. In the laboratory, vigilance studies have shown improvements after breaks of only 5 to 10 minutes (Colquhoun, 1959, McCormack, 1958, both cited in Lisper and Eriksson, 1980). In contrast, Lisper and Eriksson (1980) found no difference between 15 and 60 minute rest breaks in a field experiment.
Many rest breaks taken by drivers include consuming food. The issue of the amount of improvement that relates to the rest break alone versus the food is one that has clear practical significance.
Lisper and Eriksson (1980) found that rest breaks with food led to "a comparatively small deterioration in performance after the pause" (p.119). For those subjects who had rest breaks without food, the reaction time increase in the period before the break continued.
We have conducted several experiments on the effects of food and rest breaks on the performance of fatigued drivers at the Monash University Accident Research Centre. In each experiment, drivers performed a reaction time test, drove a simulator during the night and then repeated the reaction time test. Driver performance was measured during simulated driving in terms of the accuracy of steering. More direct measures of alertness comprised the duration and frequency of long eye closures (greater than 0.5 seconds).
The first experiment showed that the improvement resulting from a 15-minute rest break was greater for subjects who were given a snack (muesli bar and orange juice) during the break than for subjects who had a break with no snack.
A second study demonstrated that eating a snack without stopping for a rest break may provide many of the beneficial effects of stopping and eating a snack. It should be noted, however, that eating large meals (rather than snacks) can lead to a reduction in performance - the well-documented post-lunch dip (Christie and McBrearty, 1979; Colquhoun, 1982).
In summary, the studies of rest breaks suggest that they are most beneficial when taken before the driver is very fatigued and should contain food. Food alone (without a rest break) appears to have some beneficial effects. There is some evidence that a rest break does not lead to an improvement in performance, but rather a reduction in the rate of deterioration of performance.
Driver fatigue monitoring
A system for detection of driver fatigue comprises a measure of driver fatigue, a standard against which the value of the measure is compared and a mechanism of communicating a finding that performance is degraded (Haworth, 1992). Systems have taken two forms: performance tests (administered before work or at the roadside) and invehicle systems.
Automotive manufacturers have considered the possibility of invehicle systems for detection of driver fatigue since the late 1960s (see Bishop, Madnick, Walter and Sussman, 1985 for a review of early systems).
The major issues relating to the feasibility of invehicle systems appear to be the need for high detection and low false alarm rates and whether this can be achieved at a realistic cost (Haworth, 1996). The proposal of a two-step detection procedure, unobtrusive measurement of vehicle control then a verbal secondary task (first suggested by Hardee, Dingus and Wierwille, 1985, cited in Haworth, 1996) may be simpler and cheaper than collecting eye closure or other driver variables in addition to steering wheel angle.
Pavement treatments
In overseas studies pavement treatments have been shown to be effective in alerting the dozing driver.
The best known are rumble strips which are grooves or raised ridges in the asphalt of the shoulder. Tyres running on the rumble strip transmit an audible and vibratory signal to the driver. Rumble strips have been applied to some highways which had a bad record for single-vehicle run-off-road accidents. A treatment on an interstate route running across the Mojave Desert resulted in a 49 percent drop in the number of such accidents (TR News, 1988).
The use of the classic rumble strip is limited to highways with sealed shoulders. A number of adaptations have been developed which can be applied to roads with gravel shoulders. Ridged edgelining has been extensively installed in Victoria. A series of thermoplastic ridges are applied to the road by a special applicator. The markings are highly reflective and because they are 3 mm thick, the lines are easily visible above road water on rainy days. It is claimed that the thermoplastic edgelining should last six to eight times longer than painted edge lines.
Ridged edgelining is widely used in European countries, where its use is restricted to freeways because it is considered too noisy for use in towns.
CONCLUSIONS
The vast distances to be covered in Australia have made this country a fertile ground for fatigue and fatigue research. The dangers of long hours of driving, often under monotonous and uncomfortable conditions, have long been recognised. The more recent knowledge about other factors leading to fatigue - even in short distance driving - mean that the view of fatigue as a consequence of driving too long is no longer adequate and we cannot afford to limit our thinking to strategies to limit hours of driving by private or professional drivers.
Although we often associate driver fatigue with long-haul truck drivers, it can affect all of us. Key textStrange things happen in the dead of night. A car leaves a dark and lonely highway, apparently at full speed, and slams into an unforgiving tree. Nobody sees it happen and the driver is dead. On another country road, a car drifts from its lane for no obvious reason and smashes into an oncoming truck, killing all the car's occupants.
More than likely, these crashes were caused by fatigue: drivers either falling asleep at the wheel or so exhausted they made serious – and fatal – driving errors.
Fatigue is thought to be one of the biggest killers on Australian roads, 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. This is the reason for the big difference between the lowest and highest estimates of the role of fatigue in the Australian road toll.
One study based on coronial and police reports found that fatigue played a part in only 5 per cent of fatal crashes in 1988. A more recent survey (for 1994) raised this figure to about 18 per cent. It included not only those crashes in which police identified fatigue as a cause, but also cases where the crash description suggested 'loss of concentration' had been a contributing factor. A third review found that around 30 per cent of rural crashes in Western Australia could be attributed to fatigue. And a fourth study, by the Australian Transport Safety Bureau, reckoned that fatigue was a factor in over 16 per cent of the total crashes on Australian roads in 1998.
In the Australian Transport Safety Bureau study, fatigue-related crashes were defined by first excluding all crashes involving alcohol, unlicensed drivers or pedestrians and those occurring in areas where the speed limit was less than 80 kilometres per hour, and then counting all remaining head-on crashes and any single-vehicle crashes between midnight and 6 am, and between 2 pm and 4 pm (the two periods of the day when the effects of fatigue are most evident). This is a pragmatic definition; it has the advantage of being repeatable in other studies, but it risks missing some crashes in which fatigue was a factor and of counting others where it wasn't.
Why does fatigue cause accidents?
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:
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.
What sleep does
Scientists have identified five stages of sleep:
Each sleep cycle – comprising the five stages – takes about 90 minutes. Thus, someone sleeping for 8 hours will sleep through about 5½ cycles. The different stages consume different amounts of the sleep quota: stage 1, for example, usually makes up less than 10 per cent of a full night's sleep, while the REM stage might span about 25 per cent (although percentages vary by age group).
Surprisingly little is known about the physiological role of sleep and the ways in which it restores the brain to its full functions. But the effects of fatigue on the brain can be measured. Studies have shown that after 24 hours of sustained wakefulness the brain's metabolic activity can decrease by up to 6 per cent in total and by up to 11 per cent in specific areas of the brain – particularly those that play a role in judgement, attention and visual functions.
Measures to prevent fatigue-related crashes
Changes to road design, such as those listed below, could help prevent fatigue-related crashes:
Public education campaigns to warn of the dangers of driving while fatigued also play an important role in reducing fatigue-related crashes.
Managing fatigue
It is clear that the best way to manage fatigue is simply to get enough sleep. Medical researchers suggest that 8 hours a night is about the right amount for most people, although some, particularly those with sleep disorders, might find this difficult to achieve.
Other fatigue management techniques might help. For example, recent research at Flinders University has shown that subjects waking from a 10-minute nap demonstrate an immediate significant increase in alertness and mental performance that lasts for at least an hour afterwards. In contrast, a 30-minute nap fails to produce a similar immediate increase (although it does induce an increase about 30 minutes after the end of the nap). One useful practice for fatigued drivers, then, is to pull over and take a short 'power' nap.
Various road-safety publications outline other fatigue-management techniques. For example, VicRoads advocates that drivers should:
Maintaining a sensible sleep regime is the key. Driving and drowsiness are not good bedfellows; in the dead of night, it's better to wrap yourself around a pillow than around a highway ghost-gum.
Circadian rhythms at the molecular levelResearch into circadian rhythms has begun to shed some light on the phenomenon. Much of the research has been done on Drosophila melanogaster, a species of fly often used in genetic studies. By deliberately mutating the genes of these flies and then screening for changes in the circadian rhythm, scientists were able to identify the genes for controlling circadian rhythm – at least eight genes are thought to play a role. These genes were then sequenced – that is, the specific DNA code for the gene was determined – and the proteins produced by the genes identified. Scientists then worked out what these proteins did and how the circadian ‘clock’ actually operated.
Negative feedback loop
According to a simplified model, two genes called period and timeless code for the manufacture of two proteins called PER and TIM respectively. When the concentration of PER and TIM reaches a threshold level they are transported into the cell nucleus where they bind to transcription factors (proteins that initiate the transcription of a gene), shutting down further production of the two proteins; this is called a negative feedback loop. The concentrations of PER and TIM in the cell then declines as the existing molecules degrade; once the lower threshold concentrations are reached, their manufacture commences again. This rise and fall in the concentration of PER and TIM occurs on a roughly 24-hour cycle and is thought to play a major role in governing the circadian rhythm in Drosophila.
Resetting the biological clock
Similar but much more complex processes have now been identified in mammals. In humans (and many other species) the biological clock appears to work on a cycle between 24 and 25 hours in length. Under normal circumstances the biological clock is regularly ‘reset’ by a range of environmental cues, or ‘zeitgebers’ (‘time-givers’), the most important of which is light; thus, jet-lag is not a permanent condition because the internal clock will eventually be reset to match the new real-world conditions.
Sleep disordersNarcolepsy is a rare sleeping disorder with some obvious potential hazards for drivers. Sufferers commonly have 'sleep attacks' in which they fall asleep without warning, often in inappropriate settings and even after a good sleep the night before. The sleep episode lasts for anywhere between a few seconds and an hour and often features the rapid-eye-movement (REM) stage of sleep. Other possible effects of the disorder include hallucinations, temporary paralysis on waking, and cataplexy, which is the loss of muscle control in emotional situations. It appears to be genetically based and can be treated with stimulants and anti-depressants.
Obstructive sleep apnoea is more common than narcolepsy, affecting perhaps 5 per cent of the population. It is characterised by the restriction of a person's airflow during sleep, caused by the closure of the upper airway. People with sleep apnoea receive inadequate quantities of oxygen while asleep, causing them to wake frequently and thus to have a fractured and less restful sleep. This in turn means that sufferers are commonly tired during the day and more prone to symptoms of fatigue, including 'microsleeps', which are sleep episodes in inappropriate settings that last a few seconds. Several factors contribute to sleep apnoea, including facial structure (ie, the narrowness of the throat), obesity and the loss of muscle tone with ageing. Symptoms may be made worse by the consumption of alcohol and tobacco.
Source: Nova: Science in the news, by the Australian Academy of Science.
Fatigue-related crashes: An analysis of fatigue-related crashes on Australian roads using an operational definition of fatigue Adjust font size: Summary
This report examines a proposed operational definition of fatigue, and the occurrence and characteristics of fatigue-related road crashes within Australia as identified by the operational definition.
Fatigue represents a significant social and economic cost to the community in relation to road crashes, especially fatal road crashes. Fatigue-related crashes are often more severe than other crashes as drivers reaction times are often delayed or drivers have not employed any crash avoidance manoeuvres. However, the identification of fatigue related crashes is hindered by the absence of a universally accepted definition of fatigue. Furthermore, it is difficult to quantify the level of driver fatigue due to the difficulties in objectively measuring the degree of fatigue following a crash.
The Australian Transport Safety Bureau (ATSB) has proposed an operational definition of a fatigue-related road crash that would provide a common, objectively based methodology. This definition should be useful in monitoring fatigue-related crashes and gauging trends over time or between regions. The definition is based on a set of well researched selection criteria and uses crash characteristics routinely collected by different traffic authorities.
The criteria for the operational definition implemented in this report included single vehicle crashes that occurred during critical times (midnight-6am and 2pm4pm), and head-on collisions where neither vehicle was overtaking at the time of the crash. Excluded were crashes that occurred on roads with speed limits under 80 km/h, or involved pedestrians or unlicensed drivers or drivers with high levels of alcohol (blood alcohol concentration over 0.05g/100ml).
Using this criteria, this study found that 16.6 per cent of fatal crashes in 1998 involved driver fatigue. When comparing among the States and Territories, the Northern Territory had the highest rate of fatigue-related crashes per 100 million vehicle kilometres travelled (0.66). However, within individual States and Territories, New South Wales had the highest percentage of fatal crashes involving driver fatigue (22.0 per cent). The study also found that between 1990 and 1998 the proportion of fatal crashes involving driver fatigue increased from 14.9 per cent in 1990 to 18.0 per cent in 1994, after which there was a decline to 16.6 per cent in 1998. This trend was also observed when the number of fatigue-related crashes was worked as a proportion of all fatal crashes 80km/h or over. This was done to take into account the fact that the number of fatal crashes occurring in speed zones of 80km/h or over increased throughout the 1990s and that roads have also been re-zoned over this time period.
The operational definition identified a relationship between the time and type of fatigue related crashes. More single vehicle crashes occurred in the early morning (midnight- 6am) than the afternoon (2pm-4pm). However, the incidence of head-on crashes was highest between midday and 6pm and lowest between midnight and 6am, this relationship may be related to traffic densities. That is, higher traffic densities during the day would increase the likelihood of fatigue-related crashes involving multiple vehicles in head-on collisions and, conversely, lower traffic densities during the early morning would increase the likelihood of fatigue-related crashes involving single vehicles.
Some of the findings of this study were similar to other studies in that the operational definition identified a higher number of male fatigued drivers/riders than female, and more fatigued drivers/riders under 29 years of age compared with older age groups. The operational definition and other studies also found that most early morning fatigued drivers/riders were less than 29 years of age, and fatigued drivers/riders over 50 years of age were involved in more afternoon crashes than in early morning crashes.
There also appeared to be a relationship between the age of the fatigued driver/rider and the type of fatigue-related crash (single vehicle or head-on). Single vehicle crashes involved a higher proportion of fatigued drivers/riders under 29 years of age compared with head-on crashes. However, fatigued drivers/riders over 50 years of age were involved in more head-on crashes. This relationship may be linked to the time of crash. That is, single vehicle crashes are more likely to occur in the early morning and early morning crashes are more likely to involve fatigued drivers/riders under 29 years of age. Therefore, single vehicle crashes involve more fatigued drivers/riders under 29 years of age. A similar argument could explain the relationship between older fatigued drivers/riders and head-on crashes.
Using the operational definition, 29.9 per cent of fatal articulated truck crashes in 1998 involved driver fatigue, which was almost twice the proportion of all fatal crashes involving fatigue (16.6 per cent). However when speed limits were controlled for, by only including those crashes occurring at crash sites with speed limits of 80km/h or over, the difference between articulated truck crashes and all crashes was smaller. That is, in 1998, 34.5 per cent of fatal articulated truck crashes in speed zones of 80km/h or over involved fatigue, whilst 24.9 per cent of all fatal crashes involved fatigue.
The operational definition also found that the proportion of fatigue-related articulated truck crashes between 1990 and 1998 increased from 31.0 per cent in 1990 to 38.6 per cent in 1994, and this was followed by a decrease to 29.9 per cent 1998. Similar trends were also observed when speed zones were controlled, with an initial increase in the proportion of fatigue-related crashes between 1990 and 1994, followed by a decrease till 1998.
Although fatigue is more highly represented in articulated truck crashes, this does not necessarily imply that the truck driver was the fatigued driver in a crash involving more than one vehicle. The fatigued driver in a head-on crash was identified by observing which vehicle had driven onto the wrong side of the road. Therefore, in head-on fatigue related crashes involving an articulated truck, truck drivers were estimated to be the fatigued driver in only 16.8 per cent of crashes, whilst passenger car drivers were fatigued in 66.0 per cent of crashes.
The identification of fatigue-related crashes by the operational definition was compared with fatigue-related crashes identified by coroners/police. While researchers generally acknowledge that coroners/police underestimate the incidence of fatigue, it was the only measure available for comparison in this report. The operational definition compared relatively well; however, two limitations and possible modifications for the operational definition were highlighted. Firstly, nearly two-thirds of crashes identified as fatigue related by coroners/police, but not by the operational definition, were excluded because they were single vehicle crashes that did not occur during the critical time periods. Secondly, just over a third of crashes identified as fatigue-related by the operational definition, but not by the coroners/police, had been attributed to speed, drugs, or drugs and alcohol by coroners/police. This may suggest that the operational definition should be modified to exclude speed and drug related crashes, and extend the critical time periods for single vehicle crashes. However, excluding drug and speed related crashes may reduce the objectivity of the operational definition and the ability to consistently implement the definition across various traffic authorities. For instance the identification of speed involvement can vary between different traffic authorities, and not all drivers involved in fatal crashes are tested for drugs. Furthermore, extending the critical time periods may lead to an increase in the number of crashes falsely identified as fatigue-related. Clearly, more analysis is needed before the definition is modified.
In conclusion, while the operational definition may include some crashes that are not fatigue-related and exclude others that are, it nevertheless provides a practical and useful index of the relative incidence of fatigue-related crashes.
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After 17 hours awake, your brain becomes sluggish and you become unpredictable
Fatigue related accidents and sleep related accidents
Every 20 seconds a plane touches down somewhere in the UK. 
One person whose advice would be simply not to drive whilst tired is Ron Morgan. A drive home on North Yorkshire’s A19 after a holiday flight took away the most precious thing he knows and wrecked his life. Ron fell asleep at the wheel and left the road. When he woke up his wife Irene was dead. Ron says, "The grass must’ve woken me up. I saw a signpost and didn’t have time to react. It was so sudden." This is an upsetting story but not rare. Transcontinental travelers should follow Ron’s advice - there is no point in saving a couple of hours in this world to arrive years early in the next.
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Perth Australia - Driver Tiredness Warning System and Driver Fatigue Alarm Systems.