Poor sleep and crash risk

25 January 2024  By: Ruth Callaghan

Your mind begins to wander, and scenery begins to blur. Perhaps you find yourself shifting in the driver’s seat. Maybe the car feels a little warm — just enough to make you yawn. Your body starts the plunge from alert to relaxed… to asleep.

It’s the deadly decline of driver fatigue, a factor which is difficult to measure but which police suspect contributes to at least 20 per cent of fatalities and at least 10 per cent of serious injuries on WA roads.

Although most drivers think it is unacceptable to drive when you know you are too tired, a majority admit they have done this at least once.

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In 2022, 196 people were killed or seriously injured on WA roads where fatigue was suspected as a factor in the crash. And the more tired you are, the higher the risk.

The Road Safety Commission says driving after 17 hours awake is the equivalent of travelling with a blood alcohol concentration of 0.05. Driving after being awake for 24 hours is like having a blood alcohol concentration of 0.10, reducing your vigilance and coordination and increasing your reaction times.

Tiredness is a community-wide issue

The Sleep Health Foundation estimates that 60 per cent of Australians have at least one chronic sleep symptom, including trouble falling asleep, staying asleep or waking too early and not being able to get back to sleep. About half believe their daily routine doesn’t give them enough time for sleep.

Yet many people are unaware of the serious danger they pose on the roads when tired, according to fatigue risk management specialist Dr Nicholas Mabbott. This is in part because people overestimate their ability to manage fatigue. Instead of waiting to stop once they get tired, he says the key is to stop before tiredness occurs.

“If you ask people to imagine they are going to stop their vehicle and take a break because they are fatigued, and then ask how they are feeling at that point, the overwhelming majority will say ‘I'm falling asleep’,” he says.

“But that indicator comes way too late. My research in a driving simulator shows that up to 40 minutes before falling asleep, the reaction time of the driver is terrible.

“If something jumps out in front of the car, they will hit it because their reaction time has gone out by three to four seconds, and they simply aren’t making good decisions.”

Dr Mabbott has worked alongside police in analysing fatal crashes and is now a consultant through his business Beyond Midnight, working with industry groups and major employers on avoiding the risk of sleep-related incidents.

He says many drivers assume they will be fine for at least two hours on the road — something reinforced by many safety campaigns — but the fastest fatigue-related crash he’s seen came just 5 minutes and 35 seconds into a journey.

“People think you have to drive for a long time before you drive tired. We have it all wrong.”

Impaired driving starts early

Instead of the term fatigue, Dr Mabbott prefers to talk about three stages of driver impairment: tired driving, drowsy driving and sleepy driving, exacerbated by poor sleep, shift work, sleep interruptions and other medical issues like sleep apnoea.

Tired driving is the most common experience, and even though the body would like a break, many drivers are determined to push on.

At this stage, you might feel your eyes becoming a little heavy, the road becomes monotonous and you can feel a bit bored, he says. Even simple decision-making can begin to break down.

“We are all time-poor and that means we make irrational decisions, like being unable to judge the gap in traffic properly, or errors about speed,” Dr Mabbott says.

“I’ve got a golden rule that if I’ve ever slept five hours or less, I won’t drive the next day and if everyone did that, we would see an immediate drop in crash incidence. Even if you get six hours of sleep you will be impaired, though, so I like to drive on 7.5 hours of sleep on average.”

The second stage of fatigue, drowsy driving, pits the driver against a body desperate to remove the toxins that can build up during waking hours. Just as thirst signals dehydration, drowsiness is a signal that your body desperately needs rest.

“At this stage, if someone videoed you and played it back, you wouldn’t even believe these are your driving manoeuvres,” he says.

“A simple walk around won’t fix things now. You’re drowsy because your body wants you to catch up on sleep so why don’t you help it. Find a safe, secure spot, walk around a little bit, then get in the back seat, lock the doors and have a 20-minute nap. Get up, and you should be ok for another hour or two.”

Dr Mabbott describes the third stage of impairment as sleepy driving, where a driver may actually fall asleep momentarily – know as a microsleep – which puts them at a high risk of crashing.

“Please don’t get to this level but if you do, [take nothing less than] a 20-minute nap, and if you don’t feel good after that, you shouldn’t get back behind the wheel,” he says. “Contact someone to come and get you home safe.”

Some groups face a higher risk

What is critical to understand about tired driving is that it can affect anyone — no driver is immune to the effects of poor sleep — but some groups show higher levels of risk.

New parents are one of those groups, with studies finding broken sleep and inefficient sleep (being in bed but not able to sleep) can reduce reaction time and lead to driver impairment. An Australian systematic review in this area included the finding that as many as half the trips taken by parents six weeks after the birth of a baby are by a driver with high levels of fatigue.

Young and inexperienced drivers, often underestimate how tired they are, tend to continue driving even when feeling tired, and may actually be more vulnerable to the effects of sleepiness than older and more experienced drivers.

Shift workers, whose body clock has been disrupted, are at a higher risk of a fatigue-related crash, with the risk especially high when travelling home from work.

People experiencing significant life changes or stressors may also be more vulnerable to high levels of fatigue, such as those experiencing the death of a loved one or the diagnosis of a chronic health condition.

Truck drivers are also a key target of road safety campaigns, with a quarter self-reporting that they feel fatigued on the roads every day, with risks higher among those who get paid by the distance they travel.

How technology is helping

Curbing the risk of tired driving is a key plank of road safety strategies and one option might lie in better in-vehicle detection systems.

Known as Driver Monitoring Systems (DMS) or Driver Drowsiness and Attention Warning systems (DDAW), they are designed to monitor driver behaviour, using cameras and other sensors to capture and analyse information about the driver’s expression, head posture, eye area and movements.

The European Union has mandated these systems for all new vehicles starting from next year. RAC would like to see these systems considered for inclusion in the Australian Design Rules, our national standards for road vehicle safety. Technology, such as autonomous emergency braking and lane keeping assist, can also help to prevent fatigue-related crashes, underscoring the importance of choosing a modern car with a 5-star safety rating.

Other countries are also experimenting with wearable wrist watches that can directly measure biometric signs, such as heart rate, blood oxygen saturation and skin temperature.

The WA Government is currently rolling out its Regional Road Safety Program, an initiative delivering effective, low-cost safety treatments such as sealing shoulders and installing audible edge lines and centrelines across the state’s regional road network. These can help prevent fatigue related crashes by giving drivers audio-tactile feedback if their vehicle starts to drift out of the lane and by giving them more space to recover their vehicle before it leaves the sealed surface.

Behavioural changes

For the vast majority of drivers, though, small changes in behaviour are an immediate way to reduce risk, says Dr Mabbott, particularly when drivers shift into holiday mode.

“When you look at holiday driving, everyone is up late the evening before packing, there’s a degree of being anxious and we tend to get to bed late,” he says. “Then we set off early to beat the traffic, driving on too little sleep, and an hour or so into the drive the family has all fallen asleep, leaving the driver to their own devices.”

He urges drivers to ensure they get a full night’s sleep before climbing behind the wheel and puts the onus on passengers to do the right thing, keeping the driver awake and engaged.

"When a passenger falls asleep next to them, it increases the driver’s risk,” he says. “If I’m your passenger, I’m going to engage you in conversation, keep you alert and if you are starting to look tired, I’m going to insist we stop and take a break and then I’ll take over.

“It’s remarkable how often in fatigue crashes the driver had the option of swapping but didn’t. Your brain dumbs down to the point where you don’t want to change and just push on. Have a journey management plan, schedule in breaks, and plan to swap drivers when you do.”