Vulnerability to Fatigue when Driving for Work
Driver fatigue is an important risk factor in road traffic crashes when driving for work. Estimates of the proportion of road traffic crashes due to sleepiness and fatigue vary widely across studies and between nations, ranging from 1% to 33% (Garbarino et al., 2001). The lack of a standardised definition of sleep-related vehicle crashes can explain some of the variability in the findings and many fatigue-related crashes go undetected. However, fatigue effects are known to include fairly substantial driving performance decrements, as well as a reduction in the ability to maintain vigilance, attention impairment and slower reaction times to hazardous events.
There have also been several studies on time of day effects on sleep-related crashes suggesting that there are particularly high risk times to be driving. It appears that these crashes tend to follow the natural circadian rhythms our body clock when we are ‘programmed’ to be asleep. The high risk times are during the early morning (at around 02.00 – 03.00, and 06.00 – 07.00) when traffic flow rates are low and in the mid-afternoon (16.00 -17.00) at a time of high traffic density (Horne and Reyner, 1995).
Research has shown that there are a number of factors that are indicators of vulnerability to driver fatigue and these include:-
- Individuals with undiagnosed or untreated sleep disorders
- Individuals who use sleep-inducing drugs
- Alcohol consumption – even low levels
- Shift workers or truck drivers who drive for long periods
- Lack of adequate rest (less than 6 hours of sleep)
- A high frequency of night driving
- Males are at higher risk of fatigue than females
- Young drivers are particularly vulnerable to fatigue
Individual Differences in Susceptibility to fatigue
It is essential to identify those drivers that are more vulnerable to fatigue as some drivers are physiologically less able to deal with driver fatigue than others. In other words there are strong individual differences. Drivers that score high risk on the validated Driver Fatigue factor of the Fleet Driver Risk Index™ (Matthews and Desmond, 1998; Saxby et al, 2007) have been found to commit higher levels of driving errors, drive at lower speeds and have more driving penalties than drivers scoring low on this factor. The Driver Fatigue factor has also been found to be associated with self-reported crashes (Matthews et al., 1991) real crashes (Dorn et al, 2010) and performance decrements (Matthews et al., 1998). and/or risk taking amongst both commuter drivers (Dorn and Matthews, 1995) and professional drivers (Öz et al., 2010). High scores on the Driver Fatigue factor have also been found to be associated with poorer mood in real truck driving (Desmond et al, 2001).
The advantage of using the Fleet Driver Risk Index™ is that drivers more prone to fatigue can be targeted for fatigue management programmes to reduce the risk of them being involved in sleep-related crashes when driving for work. Organisations must also understand that unrealistic schedules and difficult shift patterns that disturb regular sleep can also contribute to crash risk and a review of policies should be undertaken.
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