Your car stops at a red light, and your previous late night makes itself known as you yawn sleepily. You try to keep yourself awake by rubbing your bleary eyes and blasting the air conditioning. Five minutes later, though, you can't help but admit you're on the brink of falling asleep while driving.
From a young age, we've been forewarned against the 4 Ds of driving: drunk, drugged, distracted, and drowsy. While there are tons of governmental campaigns against the first three, not much attention has been given to drowsy driving (until recently). The problem is, only a tiny bit of sleep deprivation is enough to incite sluggish steering or falling asleep while driving. The late Dr. William Dement (one of the pioneers of sleep medicine) aptly put it, "Drowsiness is a red alert." With the ever-increasing trend of short sleeping in the United States, it's obvious how prevalent — and insidious — fatigue-related driving is.
Thankfully, work is starting to be done on tackling the issue of drowsy driving. Sleep and fatigue expert Mark Rosekind (incidentally a sleep science advisor at Rise Science and a former student of Dr. Dement’s) led the National Highway Traffic Safety Administration (NHTSA) under the Obama administration to carve a new direction for lowering the incident rate of drowsy driving crashes. By late 2016, the NHTSA had developed and carried out multiple initiatives under the Drowsy Driving Research and Program Plan. With Dr. Rosekind's robust background in fatigue countermeasures, this has translated to increased awareness of sleep deprivation and driving.
Aside from governmental initiatives, there are things you can do to thwart drowsy driving. Below, you'll learn how a low sleep debt and working with your circadian rhythm are the primary safeguards in deflecting sleepiness at the wheel.
According to the NHTSA, drowsy driving is “a profound impairment that mimics alcohol-impaired driving,” and can lead to falling asleep behind the wheel. In layman’s terms, you are operating a vehicle while feeling sleepy.
Driving when you're burdened with sleep loss can have catastrophic consequences. Having just one or two hours of sleep debt (the amount of sleep you’ve missed out on in the past 14 days relative to your sleep need) is more than enough for a road mishap (more on that later). Sleepiness dulls your reflexes and impairs cognitive functions (mental processing, judgment, and decision-making) needed to keep your car in the right lane. When your reaction time slows down and your attention lapses, you're less likely to brake in time. This means you don't have to actually fall asleep while driving to do sufficient damage to yourself and others.
Even more alarming is the occurrence of microsleeps — being tired enough to unknowingly doze off for a few seconds. You may think this short period doesn't mean anything. But, when you're cruising at 65 miles per hour on a highway, those seconds can literally mean life or death. Losing consciousness for merely five seconds is enough for your car to travel more than 150 yards, plenty of distance for a fatal crash upon impact. Understandably, sleep-related vehicle accidents account for an excessive amount of rear-end and head-on collisions.
It’s also interesting to note that Matthew Walker, the author of Why We Sleep, defines drowsy driving fatalities as "road crashes" rather than "road accidents." As Walker states, "Drowsy driving deaths are neither chance nor without cause. They are predictable and the direct result of not obtaining sufficient sleep. As such, they are unnecessary and preventable."
While Americans generally frown upon drowsy driving — more than 97% of drivers show social disapproval of the behavior and roughly 96% of drivers agree that drowsy driving is perilous — about 24% of drivers admit to driving while tired at least once in the past 30 days.
The reality is, drowsy driving is more common than you might think. Some states in the U.S. do not include sleepiness or fatigue as a crash cause on their traffic crash report forms. This makes it difficult to track how many motor vehicle crashes are attributed to sluggish driving. To complicate matters, there is currently no technique that measures how sleepy a driver is, unlike the breathalyzer test for drunk driving. That being said, new research hints at a biomarker test for detecting drowsy driving in the future.
Current estimates of drowsiness-induced traffic deaths range from 2-20%, with 697 drowsy driving fatalities in 2019. That number has slightly diminished since 2017, when "91,000 police-reported crashes involved drowsy drivers," leading to nearly 800 deaths. In countries like Australia and England (which have more consistent crash reporting procedures than America), drowsy driving accounts for about 10-30% of all crashes.
The Centers for Disease Control and Prevention (CDC) share more worrying statistics on fatigue-related road accidents:
Driving when sleepy causes the individual, the economy, and society to pay through the nose. NHTSA points out at least 100,000 sleep-related crashes occur each year, costing roughly $12.5 billion in monetary terms. In another report, the estimated societal harm due to fatigue-related crashes amounts to $109 billion each year (excluding property damage).
Statistics from drowsy driving accidents share three key findings:
So, how can you tell if you or your loved one is driving drowsily? Warning signs typically include:
Sluggish steering is also more likely to rear its head when you've driven for long hours or right after night shift work. It's also worthy to note that even though rumble strips help reduce lane-drift crashes by 50% or more, they may be inadequate against drowsy driving. In one study, shift workers who hit a rumble strip while driving home after their night shifts felt alert for roughly five minutes before becoming sleepy again.
Did you know that the recycle rate of the human brain is roughly 16 hours? Prolonging wakefulness longer than that puts you at risk of sleep debt. Lack of sleep is the primary reason you're feeling drowsy at the wheel, much less falling asleep while driving.
Going without sleep for 24 hours is akin to having a blood alcohol concentration (BAC) of 0.10%, higher than every state's legal limit. But, sleep deprivation doesn't solely take the form of all-nighters. Missing one to two hours of your sleep need also counts as sleep loss.
For instance, research shows that 18 hours without sleep (which, on an eight-hour sleep need, equates to staying awake just two hours later than usual) leads to cognitive impairment distinctive of 0.05% BAC. And if you’ve slept an hour less than the recommended eight hours for 10 nights consecutively, your brain becomes as impaired as if you've skipped sleep for 24 hours.
The more sleep debt you accumulate, the more likely you are to get into a road accident caused by drowsy driving. The AAA Foundation for Traffic Safety found that up to 20% of all fatal crashes involve a sleep-deprived driver. Drivers with less than seven hours of sleep dramatically increase their chances of a collision. Sleeping for 5-6 hours doubles your likelihood of crashing compared to those who slept for seven hours or more. Most worryingly, short sleep of four hours or less increases those odds by 11-fold.
The risks are even higher if you regularly operate your vehicle when feeling lethargic. Habitually sleepy drivers, who are on the verge of falling asleep at least once every three times they drive on a highway, are 10 times more likely to crash their vehicles than non-sleepy motorists.
Unbeknownst to many people, whether you have sleep debt or not, there are times during the day when you naturally feel drowsy. These energy dips are part and parcel of your circadian rhythm (your internal body clock). They signal to your body to rest and refuel instead of getting into the driver's seat. Take note that your circadian dips will happen regardless if you had enough sleep or not. With that said, sleep debt will make you feel drowsier than you otherwise would.
All of us have two daily energy dips to watch out for, and the RISE app will show you the exact timing of both. Your first dip is the afternoon dip, and the second dip is the stretch of time comprising your evening wind-down, Melatonin Window, biological night, and sleep inertia (morning grogginess).
Below, we classify these two energy dips into three low-energy periods to highlight when you shouldn’t get behind the wheel from morning to evening:
So, how do your energy dips relate to your driving prowess? Statistics on fatigue-induced crashes show that drowsy driving usually occurs during these energy dips:
In essence, starting the ignition during your dips puts you at high risk of falling asleep while driving.
Aside from sleep debt and your circadian dips, other factors also set drowsy driving in motion:
If your health condition or medication is creating sleep problems, consult your doctor for ways to eliminate the problems and forestall daytime drowsiness. Most importantly, abstain from drinking alcohol before driving. If you have to indulge yourself, remember to wait 1-2 hours for every drink you consume. The safest option, though, is to not get behind the wheel. Instead, call for an Uber or carpool with a designated driver.
The greatest takeaway from this article is that drowsy driving is entirely preventable. But what you think may help you avoid a crash may not actually save your life. For instance, many motorists on the verge of falling asleep while driving often resort to:
Unfortunately, these techniques do not assuage sleepiness on the road. Instead, here are the measures you should take.
Keeping your sleep debt low is the only way to foolproof your driving skills against drowsiness, and you can achieve it through an ongoing practice of good sleep hygiene. Our step-by-step Sleep Guide teaches you how to hone your sleep hygiene to perfection.
Consistently meeting your sleep need (the genetically determined amount of sleep your body needs) night after night minimizes your sleep debt and how profoundly you feel your energy dips. Use the RISE app to keep a close eye on your running sleep debt to ensure it doesn't go above five hours. In that sense, RISE functions as a "breathalyzer" for drowsy driving. Knowing how much sleep debt you carry makes it easy to decide if you should get into the driver's seat or not.
Another long-term safeguard is to steer clear of driving during your energy dips as much as you can. RISE tells you exactly when your dips take place on your Energy Schedule so that you can plan ahead for alternative transportation during these periods. If you want or need to drive during your energy dips, make sure your sleep debt is less than five hours. By shunning the one-two punch of sleep deprivation and suboptimal energy levels, you'll be less likely to get into a car accident from sleepiness.
Last but not least, take note of any health issues or medications that make you sleepy all the time. Consult a qualified healthcare professional on treatment options to manage daytime sleepiness.
Besides prioritizing sufficient healthy sleep and eschewing driving during your dips, there are a few short-term measures you can use to ward off drowsy driving.
First, if you feel even the slightest bit sleepy, stop driving as soon as you can, no matter how inconvenient it is. Pull over and let someone else take the wheel. If that isn't possible, park your car in a safe location. Drink 1-2 cups of coffee (or any caffeinated beverage) before taking a 20- to 30-minute nap.
Research shows that 200 milligrams of caffeine combined with a short nap of fewer than 15 minutes eliminated mid-afternoon sleepiness for one hour. This potent duo also significantly downplayed driving incidents to 9% of the placebo group. The same study noted that caffeine alone did not completely eradicate sleepiness. Plus, the stimulant only reduced the incident rate to 34% of the placebo group.
Before taking a siesta, keep in mind that naps longer than 20 minutes are likely to trigger sleep inertia. Remember to give yourself some buffer time between waking up and driving again to ensure nap-induced grogginess doesn't affect your driving skills (even if you’ve only napped for less than 20 minutes — it’s better to be safe than sorry).
Caffeine consumption also has its caveat: Caffeine can stay in your system for up to 10 hours. Avoid drinking it too late in the day or else you risk delaying your target bedtime. This could aggravate your sleep debt and increase the likelihood of drowsy driving, the very thing you're trying to prevent in the first place.
If you intend to drive long distance, plan your itinerary for a stop every 100 miles or two hours. Keep caffeinated drinks in your vehicle in case you need an alertness boost. Also, stay away from alcohol or medications that induce drowsiness.
Drowsy driving can happen to anyone, including you. To avoid being one of the statistics listed above, practice the short- and long-term safeguards we've mentioned. Instead of looking at these lifestyle tweaks as inconveniences, think of them as your talismans against compromised road safety. With foresight and planning, you can keep drowsiness at bay when operating your vehicle.
Of course, the best way to not be inconvenienced — and avert a life-or-death situation — is to keep your sleep debt low and work with your circadian rhythm. The RISE app acts as a "breathalyzer" for how much sleep debt you're carrying to help you stay safe on the road. More than that, it shows your energy dips throughout the day so you know when you should slide into the driver's seat — and when you should not. After all, it always pays to be safe rather than sorry.
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