Sleep Talk Blog, Advice, Health & Wellbeing
Why Drowsy Driving Is Dangerous? What To Look Out For.
Why Drowsy Driving is Dangerous
The human brain needs sleep, with a lack of sleep causing cognitive impairment leading to poor judgment, concentration, and fatigue.
This is a recipe for disaster when controlling a tonne of steel. Fatigue is responsible for 10% to 20% of all road crashes worldwide, about 4% of fatal road crashes, and 2% of all collisions in the UK.
Despite the dangers, 13% of drivers admit to falling asleep behind the wheel, and the most commonly cited reason is a hard day at work.
This article explores why drowsy driving is dangerous, with advice on spotting fatigue and what to do if you are tired.
Let’s jump in!
The problem with drowsy driving
Research shows moderate sleep deprivation affects driving performance more than low-level alcohol intoxication.
The problem is that many people only associate a lousy night’s sleep with drowsiness when an exhausting day has the same effects.
When you are fatigued, blood flow and electrical activity in your brain reduce to save energy. The neural pathways that send signals from one part of the brain to the other are impaired, and this is detrimental to cognitive performance.
Your decision-making, judgment, memory, ability to speak, and high-level executive functions like problem-solving, reasoning, fluid intelligence, and planning are affected, making driving very dangerous.
Drowsy driving puts you at a higher risk of mishaps, accidents, road rage, and mistakes like speeding, even if you don’t fall asleep.
In summary – drowsiness impairs your brain like intoxication, affecting your ability to make decisions and concentrate. Even if you don’t fall asleep at the wheel, drowsy driving is dangerous, and you are statistically more likely to have an accident.
Who is likely to drive drowsy?

Drowsy driving can affect anyone, but some people are more likely to feel tired than others. Here are some common scenarios:
- People who work long hours
- People who don’t sleep well (read our sleep tips article)
- Commercial vehicle drivers
- Drivers who spend lots of time on the road
- People with sleep disorders
- People who take medications
- After drinking lots of caffeine (due to a downer)
- People who drink and drive or smoke cannabis and drive.
How to spot the warning signs
There are several signs that someone is tired:
- Excessive yawning
- Excessive blinking/twitches
- Closing eyes and daydreaming
- Rubbing eyes
- Losing balance
- Slurring speech or struggling to form sentences
On the road, look for these signs:
- Drifting between lanes
- Driving dangerously close to kerbs
- Speeding
- Trouble manoeuvring in large spaces
- Bad decision making
- Pulling out on people
If you spot these signs, the person should pull over and let someone else drive or rest for an hour before continuing.
Driving with a sleep disorder

It’s estimated that 30% of adults experience short-term insomnia, and 10% have chronic insomnia. Additionally, around 6.5% of the population has sleep apnea, and nearly everyone has trouble sleeping at least one night per week.
Simply put, sleeping disorders are relatively common.
The good news is that driving with a sleep disorder is not a problem, provided you feel alert when getting behind the wheel. However, if you have had a bad night’s sleep, you may be more tired than you think.
Consider if you are well enough to drive. Look for the warning signs you are fatigued (see above), and have a short nap before jumping behind the wheel if you are. Don’t rush home – take your time and focus on driving safely.
Summing up
Drowsy driving makes you more likely to drive dangerously and have an accident. Moderate sleep deprivation affects driving performance more than low-level intoxication, and fatigue can make you fall asleep at the wheel.
Our advice is simple – do not take risks behind the wheel. If you feel tired, take a break, and if you are a passenger, ask the person to stop.
If you enjoyed this article, check out these eight ways to sleep better.