Fatigue

Fatigue

How Effective?

Distinguishing Between Effective and Ineffective Countermeasures

Drivers use a number of ad-hoc measures to attempt to overcome the symptoms of fatigue (Nordbakke & Sagberg, 2006; Oran-Gilad & Shinar, 2000). Maycock (1995) found that 30% of drivers try listening to the radio, 68% open a window, 57% try stopping and taking a walk, 25% rely on talking to a passenger and 14% consume a caffeinated drink. Although the majority of these measures have not been proven to be very effective, they remain popular with drivers as they allow them to continue driving.

‘What many drivers fail to appreciate is that sleepiness portends sleep, which can come on more rapidly than they realise, especially if the driver has reached the more profound stage of fighting off sleep. This involves acts such as opening the vehicle’s window, turning up the radio, the driver often moving around in the driving seat—actions whereby the driver must fully realise that he or she is very sleepy. At which point the driver should stop driving as soon as possible and take a break for at least 30 minutes, drink caffeinated coffee, and if feasible, take a brief nap’ (Reyner & Horne, 1998).

Fatigue detection devices

In-vehicle fatigue detection devices can provide an insight into the driver and their behaviour whilst driving. In-vehicle systems can monitor the lateral position of the vehicle, the speed at which the driver is travelling (including acceleration levels), movement of the steering wheel and lane deviation. Behaviours such as eye movement, steering wheel grip and in some cases brain waves can also be assessed.

The European eSafety Forum (2005) attempted to calculate the benefit of lane changing monitoring systems used in Germany. It was estimated that if 70% penetration of the passenger vehicle fleet can be achieved, then 50% of all fatigue-related accidents would be affected by such a system. If this figure is correct, the study estimates that implementation of the lane changing monitoring system in vehicles would lead to a 35% reduction in lane changing related accidents (a significant proportion of which were a result of fatigue), which would equate to a 2.9% reduction in all accidents.

The European AWAKE project (http://www.transport-research.info/web/projects/project_details.cfm?id=15255) has developed guidelines for fatigue warning systems. These guidelines recognise that in order for on-road driver fatigue detection systems to be successful, they have to combine driver state (eye and eye lid movements, rate of blinking, eye closures) and driver performance measures (lane and headway tracking), as concluded by Williamson & Chamberlain (2005).

The AWAKE project has produced a set of design guidelines for assessing driver vigilance and warning signals. While these are useful in the development of fatigue detection devices, the project concludes that ‘there is no single method that is commonly accepted to detect driver fatigue’.

Wright, Stone, Horberry & Reed (2007) have undertaken a study to evaluate the sensitivity, intrusiveness, operational and market status of fifteen sleepiness detection devices. Devices assessed came under one of five categories:

  • Sleepiness detection devices based on physiological measures

  • Sleepiness detection devices based on measures of physical activity

  • Sleepiness detection devices based on behavioural measures

  • Sleepiness detection devices that used model-based predictions of sleepiness

  • Sleepiness detection devices based on combination measures

Following assessment of the devices, Wright, Stone, Horberry & Reed (2007) concluded that while many fatigue detection devices are available for use, the majority of these are ‘unsuitable for detecting sleepiness in drivers’ (p.14).

No single method exists that is commonly accepted to detect driver fatigue in an operational context. Devices based on physiological measures were too intrusive. Devices based on physical measures are not sufficiently sensitive. Devices measuring eye activity were most suitable for detecting sleepiness, although effectiveness is dependent on how the measurements are taken. Devices using a model-based approach offer some promising results, although further research is required

Rest breaks and sleep hygiene

The most effective and efficient solution to fatigue is a period of restorative rest (BMA, 2004) wherein the individual spends time sleeping (rather than simply having a break from driving but not falling asleep). Breaks, where there has been a period of restorative sleep, have been shown to improve performance and reduce subjective fatigue (Rosekind, Co & Gregory, 2000; Neri, Oyung & Colletti, 2002).

However, there is no guarantee that a rest period will restore performance to the initial level and there is little evidence regarding the necessary duration of rest periods to maintain performance. There is evidence that the restorative effect of rest periods for professional drivers declines throughout a shift.

Prophylactic (preventative) naps taken before sleep loss is accrued have been shown to be particularly advantageous for night time truck drivers (Macchia et al., 2002). There were limitations to the study; only eight drivers were used in a lab-based simulator, and data from three of these had to be discounted). Nonetheless, a three hour nap in the afternoon, between 2pm and 5pm, was shown to reduce the effects of fatigue during the following night’s shift in terms of both subjective and physiological measures. Drivers demonstrated faster and more consistent reaction times, reduced accident risk, and higher night time alertness. Macchia et al. (2002) suggest that preventative naps (taken before sleep loss has accrued) are much more effective than recuperative napping (taken when already tired) due to the improvement in performance up to 14 hours later.

Public awareness campaigns

While the relevant cross-sector literature reviewed in the development of this synthesis suggests that driver fatigue awareness campaigns are an important countermeasure, Jackson et al. (2011) states that ‘there are currently very few peer-reviewed published journal articles which have systematically assessed the effectiveness of road safety campaigns, designed specifically to target driver fatigue’ (p.56).

Jackson et al. (2011) also highlight that while regular surveys are undertaken by the UK’s Department for Transport to evaluate the extent to which drivers rate various driving behaviours as unacceptable, a research study is required to explore the effectiveness of driver fatigue Think! campaigns to measure their impact on driving behaviour and/or on driver-fatigue incidents.

The 2013 survey undertaken on behalf of the Department for Transport shows that 68% of people surveyed agreed completely that it is dangerous to carry on driving when they are too tired (TNS BRMB, 2013). This has remained relatively static since 2006.

Caffeine

Caffeine is a naturally occurring chemical that stimulates the central nervous system. It is present in many popular drinks such as tea, coffee, cola and many energy drinks. Brewed coffee has the highest caffeine content, approximately 100-150 mg/180ml; instant coffee has 60-80mg/180ml. Tea has the highest variability in caffeine content with 40-100 mg/180 ml and cola drinks have 17-55 mg/180 ml (Parkes et al. 2005).

Caffeine has numerous positive and negative physiological and psychological effects. Low doses of caffeine can increase alertness and decreased fatigue, although caffeine as a stimulant will only provide short-term benefits, somewhere in the region of two to five hours (Penetar, McCann & Thorne, 1993).

Doses of 100-200 mg of orally administered caffeine can produce more rapid and clearer thought flow and increased wakefulness and cortical arousal (the state of being awake). At very high doses caffeine can affect the cardiovascular system and result in increased heart rate, force of heart contraction and cardiac output.

Smit & Rogers (2000) demonstrated that low doses of caffeine, such as those found in a single serving of tea, coffee or cola, can enhance cognitive performance. This effect is robust for both high and low caffeine consumers. However, Smit & Rogers (2000), as cited in Parkes et al. (2009), also found that the highest doses of caffeine in the study (100mg) seemed to result in a negative effect in the mood of study participants with a higher level of habitual caffeine intake, with subjects showing signs of anger, distress and anxiety.

Brice & Smith (2002) listed more positive behavioural effects of caffeine that have been empirically demonstrated; increased alertness, faster reaction times, improved accuracy on choice reaction, improved vigilance and improved tracking accuracy (although these cannot be relied upon to offset sleep beyond the short term). All of these effects could result in improved driving performance. Increased alertness is of particular interest as it could counteract the negative impact of fatigue on driving.

Functional energy drinks

Several studies have examined the effects on driver performance of functional energy drinks. These drinks contain differing levels of caffeine, glucose and taurine, as well as glucuronolactone and a vitamin B complex.

In one study, Horne & Reyner (2001) examined lane keeping performance and reaction times of sleep deprived subjects (sleep limited to 5 hours) after the administration of 500ml of one energy drink (i.e. 160mg of caffeine). The energy drink counteracted the effects of fatigue and both lane keeping and reaction time in a low-fidelity part-task driving simulator were improved.

Parkes et al. (2001) evaluated the effects of a different energy drink on driving performance after a normal night’s sleep. Performance was evaluated during the post lunch dip in vigilance and during the evening. The drink provided 75mg of caffeine and 37.5g of glucose. This formulation was compared with a placebo which was matched for colour, taste and temperature. Both drinks were administered in a single 250ml dose.

Self-reported scales of sleepiness indicated that both drinks had an alerting effect, however, the level and duration of the alerting effect was greater for the energy drink than for the placebo. The energy drink also improved performance in hand-eye coordination resulting in better lane keeping performance during a simulated driving task. Finally, in the placebo condition the drivers tended to drive faster in traffic than in the energy drink condition. The energy drink did not produce any benefits on other performance measures such as speed variability and situation awareness.

It is worth noting that the effects were consistent (statistically significant), but quite small and the authors conclude that functional energy drinks should not be used as a perceived cure for driver sleepiness.

Cold air and use of the radio

Horne & Reyner (1997) evaluated the effects of cold air and having the radio on to maintain driver alertness. Targeting young drivers, subjects were required to drive for 2.5 hours. This included 0.5 hours for adaption to the vehicle and a further 2 hours using a combination of treatments as a control (cold air, radio or nil). They found that the capability of air and radio to counteract driver sleepiness fell below the effects shown by research into the effects of caffeine and a short nap (15 minutes). Results demonstrated that radio had a marginally better and sustained effect than cold air, although it was concluded that neither treatment was suitable as a sustained counteraction of sleepiness. Finally, it concluded that in practical terms, these treatments may serve to allow drivers to find a suitable place to stop and take an appropriate break.

Work organisation

Work-related driving poses a considerable risk on UK roads and fatigue is a primary contributory factor (Jackson et al., 2011). Research studies and analyses of crash data show that many professional drivers, in particular drivers of large goods vehicles, often obtain inadequate sleep, report elevated levels of sleepiness, and are involved in a disproportionately high number of fatigue-related accidents (Parkes, Gillan & Cynk, 2009).

To combat driver fatigue the European Union has implemented a number of regulations and directives (Regulation EC 561/2006, Directive 2002/15/EC and Directive 2003/88/EC). Regulations and directives attempt to provide a standardised approach to limits on driving time and requirements on drivers to take minimum breaks and rest periods. For example, key requirements of the Regulation EC 561/2006 are:

Daily driving time should not exceed more than 9 hours per day, with the exception of two days per week where the maximum driving time can increase to 10 hours. The maximum weekly driving time should not exceed 56 hours, although driving time of two consecutive weeks should not exceed 90 hours. Drivers should not drive for more than 4.5 hours without a break of 45 minutes (separable into 15 minutes followed by 30 minutes). In every 24 hour period, the driver must take at least 11 hours rest, although this can be reduced to 9 hours no more than three times per weekA driver is required to have 45 hours of continuous rest in any 7 day period

Every two years the European Commission compiles a report on the effectiveness of working time rules across member states. The 2012 report, analysing data from 2009-2010 (European Commission, 2012) states that ‘Member States have emphasised that enforcement of working time rules for mobile workers is in practice a very complex, burdensome and labour-intensive process. Checks on drivers that work for several employers are even more challenging’ (p.17).

In relation to offences against working time rules, the EU reported that ‘If the offence is not regarded as very serious, the first step is to issue instructions to the employers…If the employer does not comply with such requirements within the given period, the responsible inspection authorities will report this as an offence. However, serious offences are reported immediately, which would lead to a penal order or notification to the occupational safety and health authorities, who will determine whether monitoring of the company needs to be stepped up’ (p.15).

Parkes et al. (2006) report on an Australian scheme designed to manage driver fatigue. In September 2008 regulations for drivers hours changed in Australia, with the introduction of the Heavy Vehicle Driver Fatigue Reform (HVDFR). Because Western Australia and the Northern Territories are large, sparsely populated areas, some rules are not practical. Therefore, drivers in these areas operate under a Fatigue Management Code of Practice. This allows organisations to adopt standard hours, Basic Fatigue Management (BFM) or Advanced Fatigue Management (AFM).

Most organisations adopt the standard hours option (Parkes et al., 2006). This is despite the fact that adoption of either BFM or AFM would provide a greater degree of flexibility in the driver’s hour’s rules in return for the implementation of improved fatigue management systems. The 2008 regulations for drivers hours made all parties (from the driver, the employer and operator) in the ‘chain of responsibility’ responsible for managing driver fatigue. As such, reasonable steps must be taken by all parties to prevent fatigue. This includes:

  • Developing an industry code of practice

  • Use of accreditation schemes

  • Review business practices

  • Adopting a risk management approach

Technology

Many vehicle manufacturers have implemented accident avoidance features in some of their vehicles. For example, Ford's ‘Accident Warning with Brake Support’ system provides a warning; if the driver does not react, the system will apply the brakes accordingly. Volvo's ‘Accident Warning with Auto Brake’ system ensures that the car brakes by itself if the system considers that an accident is imminent and there is no intervention from the driver. These systems provide opportunities to minimise the impact of an accident resulting from severe fatigue or distraction.

Cotter, Reed & Wright (2006), as cited in Charman (2009), conducted a review of eleven sleepiness detection devices. These included devices based on measurements of eye movements, driver behaviour (including steering and lane deviations), fatigue models, and on a combination of these approaches. The review assessed the scientific validity of the technologies, their intrusiveness, their availability, their cost and their suitability for alerting drivers to fatigue.

The review showed that detection technologies available at that time were being used to warn drivers of unexpected sleepiness rather than keep the driver awake. This was a concern raised by Jackson et al. (2011) who suggest that these types of devices only respond once a driver’s performance is already significantly impaired due to fatigue. As such drivers may continue to drive until devices are activated, believing that activation of the device will allow them to react appropriately if necessary, rather than acting responsibly when identifying the signs that they are fatigued. Jackson et al. (2011) advise caution in the use of such devices.

Although there are many devices available on the market, there is little comparative research quantifying the effectiveness of the devices. Cotter, Reed & Wright (2006), as cited in Charman (2009), identified the need for independent studies evaluating the utility, costs and benefits of such devices to determine whether or not these technologies represent a good opportunity for managing fatigue across the UK road network. Such research has not yet been completed.

Highway design

A number of highway safety features exist relevant to alerting fatigued drivers of an impending danger by causing the vehicle to vibrate and generate an audible rumbling noise. These include rumble strips and patterned road markings.

Literature provides no clear evidence of the effectiveness of rumble strips on the approach to a change in speed limit, roundabout or toll. However, research undertaken in the USA shows that continuous hard shoulder rumble strips, as are also used on motorways in the UK, can reduce single-vehicle run-off road accidents by approximately 20% (Griffith, 1999; Hanley et al., 2000).

Negatively, research shows that drivers proactively rely on these features to protect themselves against the effects of fatigue. Nordbakke & Sagberg (2007) found that 63% of surveyed drivers believed that rumble strips will wake a driver who has fallen asleep. This is despite a simulator study that found that the alerting effects of a rumble strip only lasted for up to five minutes before sleepiness returns (Anund et al., 2008).

Special focus on sleep apnoea

Sleep apnoea is a disorder where an individual has one or more pauses in breathing while asleep. Pauses can last from a few seconds to minutes, and may occur over 30 times an hour. It is usually a chronic condition that disrupts sleep and sleep quality. Studies in the USA, Australia and Sweden have indicated that Obstructive Sleep Apnoea (OSA) is prevalent in 12% to 17% of professional drivers (Talmage et al., 2008; Parkes et al., 2009; Howard et al., 2004; Carter et al., 2003).

Estimates suggest that approximately 80% of people with the disorder are either unaware or do not seek diagnosis (Gibson, 2005; Finkel et al., 2009). Hack, Choi & Vijayapalan et al. (2001) identified that OSA can grossly fragment sleep, which in turn produces excessive daytime sleepiness that is likely to result increased road traffic accident rates.

Ellen et al. (2006) and George (2001) established that untreated OSA results in a higher accident risk, potentially two to three times higher than other drivers. Since around 25% of commercial motor vehicle drivers are estimated to suffer from OSA, organisations should seek to educate their drivers and carry out OSA screening programs to help reduce the effects of the condition.

Continuous positive airway pressure (CPAP), a treatment that uses mild air pressure, via a ventilator, to keep the airways open, has consistently been proven to improve driving performance and reduce accident risk by reducing daytime sleepiness with two to seven days of treatment (Ellen et al., 2006; Tregear, Reston, Schoelles & Phillips, 2010). Despite the success of CPAP, studies have shown that approximately 25% of patients with OSA discontinue therapy in the long-term (de Zeeuw et al., 2007).

Gaps in the evidence

Despite the growing concern for driver fatigue in Great Britain there are a number of limitations or gaps in the evidence. The key areas include:

  • An accurate calculation of the driver fatigue problem.

  • The current prevalence of driver fatigue in all injury classifications.

  • The level of restorative sleep required to re-establish sustainable levels of cognitive and motor function performance.

  • The need for independent studies to evaluate the utility, costs and benefits of sleep detection devices to determine suitability for managing driver fatigue across the UK.

 

  • Date Added: 03 Apr 2012, 08:13 AM
  • Last Update: 26 Jan 2017, 04:20 PM