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Questions And Answers

How Much Sleep Do You Need to Drive a Car Safely?

According to a recent survey, 53% of Americans admitted to driving when they were tired, and 19% admitted they’d actually dozed off at the wheel. Given that drowsiness and drunkenness affect the brain in similar ways, this is a very worrying statistic.

Long commutes, irregular shift patterns, and busy social lives may be to blame for this phenomenon. Many of us feel under pressure to get from A to B as quickly as possible – no matter how tired we feel.

In this guide, we’ll discuss how much sleep is required to be a safe driver. Let’s also explore how to prevent tiredness and stay alert at the wheel.

Sleep Requirements for Safe Driving

According to the US Department of Transportation, the only way to guarantee safe driving is to get 7-8 hours of good-quality sleep each night. It’s not necessarily that simple, though. If you want to drive safely, you’ll need to be aware of the following factors:

  • The signs of drowsiness can be difficult to recognize, so you’ll need to stay vigilant.
  • Certain groups of the population (truck drivers, teenagers, people with sleep disorders, etc.) are more susceptible to falling asleep at the wheel. If you fall into one of these categories, extra precautions are required.
  • Prevention is always better than the cure, but tiredness is sometimes unavoidable. If you’re nodding off at the wheel and there’s nowhere safe to stop, there are ways you can temporarily perk yourself up until you’re able to rest.
  • The drowsy-driving ‘laws’ vary from state to state. Also, non-government campaigners play an active role in reducing drowsy-driving crashes, so it’s important to take notice of their recommendations.

Why Is Sleep Important for Driving?

We know that sleep is important for brain health and physical health, but how can sleep help us become safer drivers?

  • Sleep Improves Reaction Times – Studies have shown that sleep-deprived individuals take longer to make decisions. In addition, people who’ve had less sleep tend to make poorer judgments when they’re rushed. Imagine how many split-second judgments you make in the course of a one-hour drive. Is there time to pull out? Should I give way? Someone’s stepped into the road – do I need to reduce my speed? You need adequate sleep to react to these scenarios quickly.
  • Sleep Improves Concentration – Our attention span lengthens considerably when we’re well-rested. If you’re driving for a couple of hours at a time, you’ll need to concentrate on road signs, traffic signals, and other drivers.
  • Sleep Improves Mood – If you’ve had 8 hours’ sleep, you’re less likely to lose your temper with fellow road users or irritating ‘back seat drivers’. Outward displays of ‘road rage’ can lead to crashes and collisions because you’re more likely to take dangerous risks when you’re feeling angry. Try to clock-up 8 hours of sleep per night so you can stay calm at the wheel.
  • Sleep Improves Spatial Memory –Sleeping for 6-8 hours (undisturbed) helps to improve our spatial memory. Spatial memory is important for learning road routes.
  • Sleep Improves Procedural Memory – Your procedural memory is your memory for ‘tasks.’ If you’re learning to drive, or you’re getting used to driving in a new vehicle, sleep will help you learn quicker. Procedural memories are rehearsed during REM stages of sleep (the best quality REM stages occur after 6 hours of sleep).

Is Drowsy Driving a Big Problem?

According to the NHSTA, 100,000 crashes reported to the US police in 2016 involved a drowsy driver. In 2016, 3,000 people died, and 76,000 people were injured in drowsy driving-related motor crashes.

So, the short answer is – yes, drowsy driving is a huge problem. Unfortunately, many motorists are unaware of the risks of drowsy driving. This is because drowsy-driving crashes are sometimes misreported as drowsiness can be hard to ‘prove.’

How can you avoid driving while tired?

Thankfully, there are many things you can do to stop yourself from falling asleep at the wheel. Let’s start by learning how to recognize the signs of fatigue.

Signs You’re Getting Sleepy at the Wheel

Drowsiness can be very hard to recognize. According to the Foundation for Traffic Safety, we have a ‘limited ability to predict sleep’ when we’re tired at the wheel. Fatigue can creep up on us, and we may not realize until it’s too late. If you experience any of the following symptoms when driving, you must act immediately:

  • Frequent yawning
  • Heavy and itchy eyes
  • Blurred vision/ inability to read road signs
  • Irritability and short temper
  • Inability to drive in a straight line
  • Head and neck starting to droop (head nodding)
  • Microsleeps – Dozing off for two-three seconds

Symptoms like these should never be ignored. A little later in this guide, we’ll explore some short-term solutions for fighting tiredness.

Why Are Microsleeps So Dangerous?

During microsleeps, our brainwaves change from an alpha state to a theta state. In other words, brain activity slows down considerably. During a ‘microsleep,’ we become completely unaware of our surroundings.

Imagine you’re traveling along a highway at 70mph, and you fall asleep for just 5 seconds. That means you’d travel 157.5 meters ‘blind.’ Added to which, microsleeps can last for up to 30 seconds! It’s easy to see how microsleeps lead to crashes.

Perhaps the most dangerous thing about microsleeps is our inability to recognize them. Most of the time, you won’t even be aware you’ve had a microsleep. This is worrying because it stops you from intervening and taking some much-needed rest.

Even if microsleeps do not immediately lead to a collision, consecutive microsleeps will impair your judgments. Studies have shown that having several microsleeps (one after the other) will lead to confusion and distress. Tasks like giving way, changing lanes, or slowing your speed can become incredibly difficult following a couple of microsleeps.

How to Perk Yourself Up in the Car

If you’re feeling weary at the wheel, the ideal thing to do is stop your car and sleep for 8 hours. This option is not always practical. If you’re on a busy highway, it may not even be safe to stop your vehicle. If you find yourself in this situation, consider the following short short-term solutions.

If You Can’t Immediately Stop the Vehicle:

  • Open the car windows and allow some fresh air to circulate
  • Turn the radio on (play some upbeat music)
  • Ask a passenger to talk to you


According to the NHTSA, you should look out for a designated rest place and take a nap as soon as you feel tired. Ideally, naps should last 45 minutes, but a 10-20-minute nap will also help. Studies have shown that napping can increase alertness for 2 – 3 hours.

How long is it safe to drive in one day?

When you wake up from your nap, wait for 5-10 minutes before driving off. This will ensure you are fully awake and ready to face the rest of your journey.

Caffeinated Drinks

Coffee is another short-term solution that can help you feel more awake. According to a study published by the Transportation Research Board, caffeine helped sleep-deprived drivers maintain the correct speed and stay in the correct lane during a driving simulation.

In this study, the drivers were given 4 x 200mg of coffee over the course of 24 hours (200mg is equivalent to one strong cup of coffee).

The NHTSA recommends drivers pull over and drink 1-2 cups of coffee (or a caffeinated beverage) as soon as they feel sleepy. Drivers should rest for 15 minutes before driving off to allow the effects of caffeine to take hold.

Caffeine is a short-term solution and should not be used regularly. You should limit your intake to four cups of strong coffee per 24 hours. This is because too much coffee can cause other health problems and make it difficult to recognize microsleeps.

Clearly, these short-term solutions are less than ideal. Prevention is always the best course of action when it comes to drowsy driving. Let’s discuss the issue of prevention in more detail.

How to Prevent Drowsy Driving

Did you know, sleeping for only four hours increases your risk of having a crash by 11.5 times?

If you work long night shifts at work or you’re used to grabbing sleep whenever you can get it, you’re probably skeptical about the possibility of sleeping for 8 hours a night.

Try some of the following tips and see if they make a difference:

  • Practice Good Sleep Hygiene – Try to go to bed at the same time each night to establish a healthy sleep routine. Remember, you should aim for 7-8 hours’ sleep per night, so set your bedtime accordingly. Make your bedroom as dark as possible to encourage melatonin production and keep electronics out of the bedroom if possible.
  • Sleep Comfortably – When it comes to getting a good night’s sleep, don’t underestimate the importance of comfort. Choose a good quality mattress and memory foam pillows to relax.
  • Eat a Healthy Diet – A study by the FMCSA found that CMV drivers who had drowsy-related crashes often had poor diets. Indeed, sleep deprivation can lead to overeating because it interferes with appetite regulation. Try to eat regular, balanced meals to avoid your hunger fluctuating. Also, avoid eating heavy meals before bed as these can disturb sleep.
  • Manage your Working Hours – Many of us take on regular overtime to help pay the bills. It’s not only truck drivers and taxi drivers that can suffer drowsiness at the wheel; it’s an overworked person who drives as part of their commute. Try to manage your workload as much as possible, and ensure you’re sticking to your employer’s policy for fatigue prevention.
  • Stay Hydrated – Keep a bottle of water in the car to help you stay hydrated. You’ll find it a lot easier to concentrate on the road!
  • Avoid Drowsy Meds – The FMCSA found that 17% of drivers involved in crashes had taken over-the-counter ‘drowsy’ medications in the 12 hours before the crash. It’s common for OTC cold, flu, and hay fever medicines to make you drowsy. You should completely avoid driving when you have the flu as influenza can interfere with your reflexes. If you have a light cold or hay fever, choose ‘non-drowsy’ medications if you know you’ll be driving.
  • Share the Driving If Possible – If you’re going on a long road trip, try to share the driving with a friend or family member.
  • Plan Your Route – Where possible, plan your route beforehand so you can schedule some rest breaks into your journey. This will also help to take the stress out of your journey, so you’re free to concentrate on driving.

When to Take Extra Care

Certain factors can make drowsy-driving crashes more likely. Consider these factors when you’re planning car journeys.

Driving on the Freeway

Crashes caused by tired drivers are more likely to occur on the freeway. This is because the driver lacks stimulation, so may become overly relaxed. If your journey incorporates long and boring roads, play some of your favorite music, or listen to an interesting radio program to help keep yourself focused.

Naturally Occurring Lulls

Our sleep/wake cycle operates according to a 24hour clock – this is known as our ‘circadian rhythm.’ At certain points in this cycle, our energy levels plummet.

How to Stay Awake on the Road

Our energy levels are known to dip at the following times:

  • Midnight – 2 am
  • 12 am – 6 am
  • 2 pm – 4 pm

Studies have shown that crashes caused by drowsy drivers are more likely to happen during these hours. If you’re driving a long distance, schedule your rest breaks during these hours. If you must drive at these times, consider drinking a cup of coffee and be extra vigilant regarding symptoms of drowsiness. But, don’t drink coffee before you go to bed.

Sleep Inertia

Crashes are more likely to occur during the first hour of driving. This could be because the driver hasn’t allowed themselves sufficient time to wake up from sleep. Truck drivers who sleep in their berths are most at risk of this phenomenon, as they’re more job-focused and are less likely to allow themselves time to wake up slowly.

Truck Drivers and Drowsy Driving

According to the Department of Health and Human Services, truck drivers should aim for 8-9 hours’ sleep (rather than the standard 6-8 hours’ sleep). In an ideal world, we’d all get as much sleep as we need. Unfortunately, we know that sleep can be particularly challenging for people who drive long distances and spend regular time away from home.

If you’re a long-distance driver, consider the following tips (in addition to the preventative steps already mentioned):

  • Explain to Friends and Family – When your home to rest, explain to your friends and family the importance of sleep. If they know how crucial your sleep is, they’re less likely to disturb you. Studies have shown that we’re more likely to make positive behavioral changes if we have the support of our family.
  • Stress Relief – Being a driver can be stressful and isolating. During your time off, find ways to relieve stress but avoid ‘stimulants’ like nicotine and alcohol.
  • Prevention Naps – According to the FMCSA, it’s more effective to nap before you feel tired. If you regularly drive long distances, make sure you plan naps into your journey.
  • Sleeping on the Road – Try to pick a spot that is safe to park in, but still fairly quiet. Make sure the temperature of your berth is conducive to sleep and consider buying a good quality pillow to help you feel more comfortable. Put a blue filter on your phone if you keep it close to your bed.

Teenagers and Drowsy Driving

There are two key reasons why teenagers must take extra precautions to prevent drowsy driving.

Teenagers’ brains are still developing, so their sleep requirements are greater than adults’. Teenagers should regularly sleep for 7-9.5 hours per night. At the same time, teenagers often stay up late and pull ‘all-nighters.’ This means they are particularly susceptible to becoming tired at the wheel.

Secondly, teenagers are inexperienced drivers. Sleep will enable them to become better drivers because good quality REM sleep strengthens procedural and spatial memory skills. If they miss out on their sleep, they’re more likely to be hesitant drivers. So, if you’re a teenager who regularly drives, you must get high-quality sleep!

Sleep Disorders and Drowsy Driving

The American Sleep Association estimates that up to 70 million Americans suffer from chronic sleep disorders. The most prevalent sleep disorders that may directly affect a person’s ability to drive are sleep apnea, narcolepsy, and insomnia.

Regulations regarding driving with narcolepsy vary from state to state. In most states, your doctor will be required to contact the DMV if you are suffering from any condition that may cause a loss of consciousness.

The FMCSA state that a person may not be qualified to hold a commercial driving license if they suffer from a condition that can affect their ability to operate safely (i.e., untreated or severe sleep apnea). Procedures vary between states, though a diagnosis of sleep apnea would rarely stop someone from driving domestically.

Anyone with concerns regarding sleep-related issues should not be deterred from consulting their doctor and receiving treatment.

Drowsy Driving vs. Drunk Driving

When it comes to driving – feeling very sleepy can be just as dangerous as feeling drunk. The cognitive effects of being drunk (poor coordination, slower judgments) are similar to the effects of being tired.

According to a study published by NCBI, after 17 hours of no sleep, cognitive performance is comparable to having a blood alcohol volume (BAC) of 0.05. After 24 hours of no sleep, your brain responses indicate a BAC of 0.10. Most US states set their BAC levels at 0.08, so you’re essentially over the legal limit if you drive after being awake for 24 hours.

is it illegal to drive while sleep deprived?

After 36-48 hours of no sleep, you’re likely to experience hallucinations, severe memory loss, and regular microsleeps. Clearly, it would be dangerous to drive in these conditions.

With all this in mind, surely drowsy driving carries similar penalties to drunk driving?

Is It Illegal to Drive While Tired?

The law regarding fatigued driving varies from state to state. The only states to specifically legislate against drowsy driving are Arkansas and New Jersey.

Maggie’s Law – New Jersey

Named after Maggie McDonnell, a sleep-deprived driver killed in a 1997 crash, New Jersey’s ‘Maggie’s Law’ (National Driving Act of 2003) was the first US law to specifically target drivers who have not slept for 24 or more hours.

Under Maggie’s Law, drivers found to have caused death due to sleep-deprived driving may be prosecuted for ‘vehicular homicide’ carrying a maximum sentence of 10 years imprisonment and up to a $100,000 fine.

The law has been notoriously difficult to enforce, with only two convictions since its enactment in 2003.

Negligent Homicide – Arkansas

In 2013, Arkansas made drowsy driving an offense under its existing negligent homicide laws. The change in law classed fatigued driving as a Class B felony.

If a driver is convicted of causing death due to driving while fatigued, they could be imprisoned for up to 20 years (and be fined up to $15000). Three people have been convicted since this law came into effect.

What Is Being Done to Help?

Although laws have been difficult to implement, charities, employers, and local governments are working hard to reduce the number of drowsy-driving road accidents.

Rumble Strips

Crashes caused by sleep deprivation are often ‘roll off the road crashes.’ An effective countermeasure to this type of crash is the installation of ‘rumble strips’ along the edges of roads.

These rumble strips are patterns in the tarmac that, when driven over, cause vibrations – alerting the driver that they are leaving the edge of the highway. In certain locations in New York, rumble strips reduced ‘roll off the road’ incidences by 84%.

Drowsy Driving Awareness

Each November, the National Sleep Foundation holds a Drowsy Driving Prevention Week to raise awareness of the dangers of driving with insufficient rest. The foundation releases facts and figures related to drowsy driving and educates people on the risks of driving without sufficient sleep.

Some states have their own awareness initiatives. Alabama and California have designated ‘drowsy driver awareness days’ (November 19th and April 6th, respectively), and Florida and Texas promote ‘drowsy driver awareness weeks’ in September and November.

Employer Responsibility

To reduce sleep-related accidents, employers must play their part. Driving-related industries such as trucking companies, couriers, and taxi firms are responsible for abiding by national legislation regarding working hours.

In February, Uber introduced new policies, stipulating that drivers must take a minimum of 6 hours rest following 12 hours of work. However, individual employers have limited control over people who work multiple jobs, so employees must share some of the responsibility, too.

Staying Alert at the Wheel

For the most part, tiredness is a personal complaint. However, when you get behind the wheel of your car, your tiredness could affect hundreds of other road users. For this reason, you need to take drowsiness as seriously as other cognitive impairments – such as driving under the influence.

As we’ve discussed, concentration, judgment skills, and reflexes are significantly impaired when you’re tired. If you want to be a safe driver, you’ll need to regularly clock up 6-8 hours of sleep. If you drive as part of your job or are a teenage driver, get 8-9 hours of sleep.

Remember, if you need to fight fatigue at a moment’s notice, use caffeine, naps, and music (appropriately) to help perk yourself up.