What is driver fatigue?

Many of us immediately think of driver fatigue as the holiday thing, meaning that it is only important when we drive long distances during holiday periods. Not true! Driver fatigue is also not just falling asleep behind the wheel of a vehicle. There are many factors involved here.

It is just as big issue during our daily commuting as with long distance driving, if not bigger. Statistics and research show that most fatigue related crashes happens within twenty minutes from home or on trips of two hours or less. We tend to focus on the consequence or result, such as losing control, jumping a red light, inattention, etc. However, the foundation of the problem may well be tired drivers. There will be exceptions to this where drivers consciously make mistakes and where fatigue is not a factor.

Driver fatigue is one of the most underrated causes of crashes worldwide. Some countries estimate that driver fatigue is prevalent in as much as 30 percent of all injury crashes. Here in New Zealand the figure is around 20 percent. It was not until recent years that driver fatigue has officially been acknowledged as being a factor in crashes.

What are the warning signs of driver fatigue?

In general, there are several signs that indicate driver fatigue. The following is a list of common indicators:

  • Frequent yawning or blinking;
  • Difficulty in keeping your eyes open;
  • Feeling irritated;
  • Finding it difficult to keep your speed consistent, like slowing down or speeding up;
  • Trouble to stay focussed on your driving task;
  • Slow reaction, like braking too late;
  • Making wrong choices;
  • Taking unnecessary risks;
  • Travel over some distance without remembering doing it;
  • Trouble keeping your head up;
  • Drifting all over the road, like over the centre line or too close to the side of the road;

What causes driver fatigue?

Again, there are various reasons, but the following are the most common ones:

  • Lack of sleep;
  • Concentration on driving task;
  • Tired after a full day at work;
  • Illness and/or medication;
  • After a long flight.

The science of sleep


Micro-sleep is those few seconds you doze off whilst driving when you are fatigued. If you drive at 100km/h, the vehicle travels 27 meters per second. In this case, during a 4-second micro-sleep, the vehicle would have travelled 108 meters out of control! Scary if you may be one of the drivers approaching from the opposite direction, believing every vehicle that comes closer has a driver that is in control!

Sleep and wake cycles

There are three sleep factors to consider before deciding whether to start driving – circadian rhythmssleep debtandsleep inertia.

Circadian rhythms

Our bodies are programmed by our body’s circadian rhythms to sleep at night and be awake during the day. During nighttime hours and – to a lesser extent – during afternoon siesta hours, most types of human performance are impaired, including our ability to drive.

Problems occur if we disrupt our natural sleep cycles like staying awake during the night, do not get enough sleep or get poor quality sleep.

You cannot reverse your Circadian rhythms. Even if you have been working nightshifts for many years, your body is programmed to sleep at night.

Sleep debt

Adults generally need between seven and eight hours sleep per day, depending on the individual. Some experts say teenagers need 10 to 10.5 hours of sleep.  If we do not get these hours of sleep or if we reduce it, we end up with a condition called sleep debt. The only way to resolve this is by getting enough sleep.

Sleep inertia

Sleep inertia is the feeling of grogginess you get after waking. It can affect your ability to perform even simple tasks. Sleep inertia is most dangerous for people who drive in the early morning hours, particularly shortly after waking from sleep.

Activity and noise should usually reverse it within fifteen minutes, but be aware it can last up to 4 hours. Its severity depends on how much sleep you had and at what stage of sleep you awoke.

How can drivers reduce the risk of driver fatigue? Ten points that may save a life.

  1. Never drive when you are feeling tired;
  2. Get enough sleep before the trip;
  3. Share the driving with other licenced passengers;
  4. Plan for regular rest stops at least every two hours; During this stop get out of the vehicle and walk around for at least 15 minutes;
  5. Eat light meals or fruit throughout the journey;
  6. Stay hydrated;
  7. Get fresh air – put the air vent on fresh air and not on recycle
  8. Power nap: If you find you are feeling tired during a trip then you can take a “powernap” – it is a short nap of between 20-40 minutes.
  9. Do not drink any alcohol before the trip – alcohol and fatigue make a deadly cocktail. Approximately 14% of drink drive fatalities involve driver fatigue.
  10. Stop over at “driver reviver” stops for a free coffee or stop wherever you see a fatigue stop checkpoint.

What does not work?

  • Opening windows;
  • Loud music;
  • Drinking lots of coffee or energy drinks;
  • Exercising in the vehicle.

Doing these things have not been proven to increase alertness.

Other interesting facts about driver fatigue

  • It is more dangerous to drive between 1am and 5am than at any other time of the day. The next most dangerous time is between 1pm and 5pm.
  • If you drive after staying awake for 17 hours, you will behave like a driver who is just below the legal blood alcohol limit.
  • If you drive after staying awake for 24 hours, you are just as dangerous as someone who is over the legal blood alcohol limit.

On short trips in town, take a taxi, catch a bus, or ride with a friend or colleague.

Stop – Revive – Drive