Driver fatigue kills, but do you know what it looks like?
Posted: October 4, 2019 by John G. Smith
BRAMPTON, Ont. – Clinton Marquardt knows that driver fatigue kills.
The Canadian Council of Motor Transport Administrators says it’s a contributing factor in 20% of Canada’s fatal car crashes, the fatigue specialist told the annual meeting of the Fleet Safety Council.
“Those are just fatal accidents, but that doesn’t consider the number of incidents and near misses out there,” he added. In a 2008 poll, 60% of surveyed drivers admitted to driving fatigued as well. “We all know we can drive fatigued without having a negative outcome, but there is a risk.”
If anything, Marquardt believes the transportation industry underestimates the number of incidents that can be traced to fatigue and rarely looks at it in the context of safety or accident investigations.
Normal sleep lasts about six to nine hours, he explained, adding that each hour of sleep buys about two hours of wakefulness. “You have to match quality of sleep, the [four] sleep stages, and quantity.”
Those who shortchange their required sleep by just two hours can see their performance drop to levels seen among those with a blood alcohol content of .045. A four-hour sleep debt sees performance drop to levels that compare to a blood alcohol content of .095. Let that shortage expand to 10 hours, and reaction times can slow by 140%, he said.
Drawing the link between fatigue and a collision involves determining if someone is fatigued, but also whether their actions are consistent with what might be expected from a fatigued person, he told the room of safety professionals.
“Consider the sleep debt in your assessments of accidents and incidents.”
While blood tests can’t determine fatigue, there are tools to measure sleep-related fatigue.
Consider the Epworth Sleepiness Scale to see if someone is too fatigued. He told the crowd to use a scale of zero to three, representing no chance of dozing, a slight chance of dozing, moderate chance of dozing, and high chance of dozing. Then he asked them to apply the appropriate score to a series of scenarios over the last three weeks – sitting and reading, watching TV, sitting inactive in a public place, as a passenger in a car for an hour without a break, lying down for a nap in the afternoon, sitting and talking to someone, sitting quietly after lunch without alcohol, or sitting as a passenger in a car while stopped in traffic for a few minutes.
Those who score between one and six are getting enough sleep. But most people outside transportation tend to score between seven and eight, he said.
The three-week period is important because it gets people to think beyond the moments right after a collision, when they are alert and shaken up, he added.
Other tests include the Epworth Sleepiness Scale, Karolinska Sleepiness Scale, and Samn-Perelli Fatigue Scale, although Marquardt cautions against many other online tools.
As the sleep debt grows, meanwhile, drivers can find themselves struggling with micro sleeps that last between one and three seconds, when people still see themselves as being awake. “Micro sleeps are a little bit of sleep creeping into your brain while you’re awake,” he said. But they don’t reduce fatigue.
Even before that moment, fatigue can impair physiological functions, overall cognitive functions, problem solving, decision making, memory, reaction time, attention and vigilance. “It’s much easier to become distracted.”
Linking collisions to driver fatigue
Collision investigations can also help determine if fatigue was involved in an incident.
Marquardt says fatigue can be connected to accidents sharing a variety of characteristics:
No active pre-crash maneuver such as stopping or changing lanes
Gradually drifting out of a lane
No signs of corrective action such as skid marks
A driver is the only occupant of the vehicle causing the crash. Stimulation through conversations can help to keep fatigue at bay.
The driver is a young male, typically below 30
The collision occurs between midnight and 8 a.m. – “Our bodies follow 24-hour rhythms,” he said.
The collision occurs in rural areas on roadways with speeds between 88.5 and 104.6 km/h. “It’s often straight, not much change in scenery.”
The collision itself is likely considered a serious crash.
Those details emerge after collisions, though. He also challenged employers to give employees the countermeasures to fight fatigue. “People are going to be fatigued while on duty.”
He argues that several countermeasures – splashing cold water on your face, blasting the radio, turning down the temperature, opening the window, chewing gum, or eating a snack like sunflower seeds and popcorn – are less effective.
The most effective countermeasures involve giving the brain and body what it wants, and that’s sleep. This can involve napping and controlled rest, he said, but even then it’s important to beware of sleep inertia in the moments right after waking.
He likes to combine that with 100-200 mg of caffeine. “Combine these two in a Nappuccino.”