The Consequences of Driving Fatigue

The Consequences of Drowsy Driving: The Physical Effects & Accidents

Updated June 12, 2019

So far, we have briefly touched upon the effects of fatigue on driving ability, discussed the risk factors and identified common causes. Now, let’s delve into the mental and physical effects of fatigue in more detail, to illustrate why driving when impaired by fatigue is so dangerous.

When fatigued, a person cannot perform as well as they would usually during any task. When the task in question is maneuvering a large, heavy metal object that is hurtling along a roadway at speed, persevering despite the effects of fatigue invites death and destruction.

The physical effects of fatigue

As your body becomes increasingly in need of rest, it will cease to function as well as it should. You may notice soreness, aches, pains and mild sensory issues, for instance:

  • Slightly unfocused or blurred vision
  • Tired, sore or puffy eyes
  • Muscle soreness
  • Aching or stiff joints
  • Headaches, tension around your temples or pain in the back of your head
  • Swelling or stiffness in the hands or feet

Vision impairments are common when a person is heavily fatigued. In mild cases you may not even notice that this has happened to you, though it will still be having an adverse effect on your ability to read traffic control devices and spot hazards.

What about the other physical effects in this list? They may not sound like too much to worry about but remember, experiencing any unfamiliar pain or discomfort while driving will leave you less able to concentrate on the task at hand, and more at risk of being involved in a crash.

The cognitive effects of fatigue

Cognition (your ability to perceive, consider and react to your surroundings) will also be severely impaired if you are experiencing fatigue. While under strain, your mind will struggle to process even relatively common-place events in the driving environment. It may take you longer to execute simple maneuvers and respond to dangerous situations. If a hazardous event takes you by surprise – such as a pedestrian stepping out into the roadway – you are significantly less likely to react in time to avoid a collision.

Driving safely demands building a comprehensive “mental picture” of the situation up ahead and on the roadway around you. As conditions change, the driver must update their mental picture and adjust their behavior to remain as safe as possible. This is something that most experienced drivers do without realizing it, though it takes a greater degree of concentration when you are first starting out. A driver who is suffering with fatigue will have trouble forming a complete mental picture of the roadway environment and will struggle to hold onto important details. In this situation, it is all too easy to make a fatal mistake.

Loss of judgment is perhaps the most dangerous cognitive symptom of fatigue. Even if you can accurately perceive what is going on around you, your ability to respond to the driving environment in a logical way will be hindered. You may take risky action without realizing the danger it incurs or attempt to take a shorter route despite it being unfamiliar. Worse still, you may choose to continue driving even though you are struggling to stay awake.

Other effects

In addition to the dangerous physical and cognitive effects listed above, driving when fatigued will mean:

  1. Your reaction time and reflexes are impaired
  2. You cannot accurately judge the distance and speed of other vehicles and objects
  3. You are more inclined to be distracted by minor events, such as yawning, physical discomfort, or your cell phone beeping
  4. You may feel irritable and are more likely to overreact to frustrating situations on the road
  5. You are more likely to fall victim to highway hypnosis

Microsleep in fatigued drivers

Microsleep refers to short bursts of sleep experienced when a person nods off unintentionally. A typical microsleep may last just a fraction of a second or may stretch on for several seconds. People who experience microsleep often do not realize they have lost consciousness, assuming they have simply “spaced out” for a moment. Or, they may notice the episode after it has occurred as some movement or sound snaps them back into consciousness.

Most people have experienced microsleep at some time or another. Perhaps it has happened to you while watching TV late at night or while sat in a particularly unstimulating class during the day. Obviously, experiencing microsleep while in charge of a moving vehicle would be incredibly dangerous. When struck by microsleep:

  • Your eyes may close (for longer than a blink)
  • You may stare blankly without seeing what is in front of you
  • Your head may drop forwards or backwards, startling you awake with an involuntary jerk which may cause you to turn the steering wheel sharply

When a fatigued driver experiences microsleep, they may run through a red light, meander out of their lane or plow straight off the side of the pavement if the roadway curves.

Fatigued driving accident facts

According to information compiled by the NHTSA, collisions and crashes involving fatigued drivers usually:

  • Occur after midnight
  • Involve a single vehicle leaving the roadway
  • Happen on high-speed roads where it is easy to lose focus and being able to react quickly is essential
  • Involve drivers who are alone in the vehicle
  • Involve drivers under 25 years old
  • Have a high incidence of serious injury and fatality

Fatigued crashes consequences

The consequences of a crash involving a fatigued driver are usually severe and often deadly. In most other types of crash, the driver or drivers involved generally have a moment to slow down, alter course or take some other action to lessen the severity of the incident. Having even a fraction of a second to act when you realize a crash is imminent can mean the difference between life and death.

Fatigued crashes typically have more serious consequences, as the driver involved will be operating with impaired reaction time, reflexes and judgment. They are more likely to react to the situation in blind panic and act in a way that will worsen the collision, such as jerking the steering wheel or slamming on the brakes.

If fatigue has caused the driver to fall asleep at the wheel, they will not realize they are about to crash and will not be able to take ANY evasive action. In this type of crash, the vehicle typically plows off the roadway or collides with an object at full-speed.

A fatigued driver is a ticking time-bomb!

Tired drivers often have an unrealistic sense of their ability to remain alert while driving. Keep in mind that nobody ever remembers the moment that they lose consciousness and fall asleep. You may think that it is possible to stay awake behind the wheel simply by willing it, but eventually, sleep will catch up with you. We talk about this issue and other fatigued driving myths in our next article.

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Myths About Driving Fatigue
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Drowsy Driving Myths

Driving while drowsy or fatigued is every bit as dangerous as driving under the influence of alcohol. Most drivers are aware of the effect that alcohol may have on their driving ability and would be hesitant to get behind the wheel if they have had a drink, even if they believe they are within the legal BAC limit.

Preventing Driving Fatigue
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Preventing Drowsy Driving

Rest is the only cure for fatigue. When you are tired or feeling mentally or physically drained, the only sure way to stay safe is to rest before driving, or not to drive at all. After a hard day at school or a tiring shift at work, people often force themselves to drive, thinking they will rest when they get home.

Highway Hypnosis & Velocitation
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Highway Hypnosis and Velocitation

Highway hypnosis is a dangerous trance-like state, during which a driver may travel a short distance – or many miles – without having any recollection of the experience. Velocitation is a psychological phenomenon brought on by monotonous, extended periods of high-speed driving. When velocitation occurs, a driver loses touch with how fast they are traveling and often believes they are moving slower than they truly are.

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Illness and Temporary Impairments

Driving ability can be equally as impeded by a temporary physical or mental impairment as it is by ongoing medical conditions and permanent physical disabilities. Every person experiences an illness or injury at some time or another; the fact that you are usually fit to drive does not meant that you are always fit to drive.

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Safe Driving and Aging

Getting older does not necessarily mean that you are no longer fit to drive. According to Federal Highway Administration statistics, there are more than 41 million licensed drivers in the United States aged 65 or older. Unfortunately, the physical and mental changes associated with natural aging can adversely affect driving skills and increase the risk of being injured or killed in a car crash.

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Carbon Monoxide Poisoning

Unintentional carbon monoxide (CO) poisoning is responsible for roughly 500 fatalities and 15,000 emergency room visits around the United States every year. A large portion of these poisoning cases are caused by motor vehicle exhaust emissions. All drivers must be aware of the dangers of carbon monoxide poisoning and be able to spot the symptoms when it occurs.

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The Dangers of Drowsy Driving

Most people accept being tired as a normal part of their hectic, day-to-day lives. Tiredness rarely prevents us from fulfilling our regular daily tasks, such as working, going to school or seeing our friends, so we do not assume that it should stop us from driving to and from these activities. Sadly, driving while fatigued can be a fatal mistake.

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The Causes of Fatigue

Being fatigued does not necessarily mean feeling sleepy, though it can lead to that. The term “fatigue” describes a mental and physical state which can occur following a challenging or prolonged activity. A person who is fatigued has a lower-than-normal capacity for work and concentration, while being less capable of completing any task efficiently.

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Fatigue Risk Factors

Understanding the risk factors that increase your chances of becoming drowsy will help you to make sensible driving decisions. If you know you are at risk, you are more likely to be tuned in to your physical and mental state while driving. When you notice the symptoms of fatigue taking hold, you can take steps to maintain your safety.