A late night; a double shift; a baby who won’t go to sleep or the monotony of the open road – there are many reasons for becoming drowsy at the wheel of a vehicle. Regardless of the cause, the consequences can be devastating. The proportion of accidents caused by tired drivers varies from one study to another and is generally between about 15 and 60%. Research also shows that this type of accident is often more serious than collisions caused by other factors because reaction times are delayed and evasive manoeuvres are not taken.
Dead tired
“It has been proven that it is as dangerous to drive while tired as it is to drive with alcohol in your bloodstream,” says Torbjörn Åkerstedt, sleep researcher and professor at Karolinska Institutet and the University of Stockholm.
During the course of his research, Professor Åkerstedt puts tired people into a driving simulator to study how they react behind the wheel. Many of the test subjects, after first experiencing the classic symptoms of tiredness such as heavy eyelids and yawning, slip into what is known as a microsleep, when they doze off for a few seconds – often without realising it. Volvo Trucks has developed Driver Alert Support (DAS), a sensor-based system which detects when a driver is drifting off. If the driver shows symptoms of tiredness such as erratic or jerky driving, the system sends out an audible warning and a visual signal.
“The system is invisible if you are driving well,” says Peter Kronberg, who led the technical development of DAS for Volvo Trucks. “It isn’t something that will require your attention or unnecessarily distract you while you are on the road. When it makes itself known, it does so for a very good reason – to warn you that you are a danger on the road and it is time for you to do something about it.”
However, driving ability is affected in a variety of ways in addition to the obvious consequences of actually falling asleep.
“You think more slowly, take longer to remember things, find it more difficult to learn new things and respond more slowly to simple stimuli,” says Professor Åkerstedt. “Studies have also shown that you lose control over your emotions. Being emotionally unstable is naturally not a positive characteristic when you are behind the wheel since this impairs your judgement.”
Truck drivers in focus
In one National Transportation Safety Board study, 52 per cent of single-vehicle accidents involving heavy trucks were fatigue-related, and in nearly 18 per cent of cases the driver admitted to falling asleep. The European SafetyNet (2009) Fatigue survey revealed that 60 percent of all heavy vehicle drivers have experienced drowsiness behind the wheel. However, a Finnish study* reveals that truck drivers are less likely to fall asleep behind the wheel than other road users and are involved in fewer accidents per kilometre, but because of the sheer amount of time they spend driving, they are an important group to examine.
The average long-haul driver sleeps 4.6 nights a week in the cab, according to surveys carried out by Volvo Trucks. And when the company asked 2,200 long-haul truck drivers to prioritise fifteen different in-cab parameters, top of the list was rest and sleep comfort. Today’s driving and rest regulations for truck drivers can only improve safety if the statutory rest period really does offer proper relaxation.
“A good driver’s environment is one of Volvo’s hallmarks, but it’s also as much about another of our core values – safety,” explains Carl Johan Almqvist, Traffic and Product Safety Director at Volvo Trucks. “A poorly designed driver’s environment results in poorer road safety, but a driver who is tired because he or she has slept badly is actually even worse.”
So Volvo has redesigned the bunk area of its sleeper cabs to help drivers sleep better, thereby keeping them more alert behind the wheel the next day. Beds are adjustable, mattresses are available in different firmness levels, and there is a choice of overlay mattresses to meet each individual driver’s preferences.
Take a break
So what should you do if you feel you are getting tired while driving? “Drowsiness can be counteracted by drinking plenty of coffee or taking frequent breaks,” says Professor Åkerstedt. “However, after a break you’re only alert for another 15 to 30 minutes, and the more tired you get, the faster you’ll become tired again after each break. It’s vital to be aware of your tiredness so that you can choose to act before it gets too late.”
* Markku Partinen, Kari Hirvonen: Unikuorma. Snoring and obstructive sleep apnoea among drivers of heavy goods vehicles and the effects of sleep deprivation on driving ability. Research and development 1.11.2000-15.3.2006. Final report.
The science of sleep
December 1, 2011
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Veronica Nyblom, Media Relations Europe, phone +46 31 322 09 9, email veronica.nyblom@volvo.com