Fatigue

Fatigue is often ranked as a major factor in causing road crashes although its contribution to individual cases is hard to measure and is often not reported as a cause of crash. Driver fatigue is particularly dangerous because one of the symptoms is decreased ability to judge your own level of tiredness.

Fatigue is more likely to be a factor in crashes in rural areas as they can involve long trips and extensive periods of continuous driving, however anyone can be affected by fatigue.

If you don't get enough sleep you go in to sleep debt and you owe yourself more sleep. The only way to repay this debt is by sleeping. Until you catch up on your sleep, you will have a greater risk of having a fatigue related crash.

Research has shown that not sleeping for more than 17 hours has an effect on driving ability the same as a Blood Alcohol Concentration(BAC) of 0.05. Not sleeping for 24 hours has the same effect of having a BAC of 0.10, double the legal limit.

What causes fatigue?

There are a range of factors that can cause fatigue. The four main causes are:

• lack of quality sleep
• time of day driving when you would normally be sleeping (eg 1am-6am) or in the afternoon period (eg 2pm-4pm) when our biological time clock makes us feel tired
• length of time performing the task
• sleeping disorders such as sleep apnoea.

Signs of fatigue include:

• constant yawning
• drifting over lanes
• sore eyes
• trouble keeping your head upright
• delayed reactions
• day dreaming
• difficulty remembering driving the last few kilometres
• variations in driving speed.

Most importantly if you feel tired, pull over and have a power nap, otherwise you may experience microsleeps which are dangerous while driving. Once you are fatigued the only cure is to stop and take a break.

Microsleeps

Microsleeps are when you nod off for unintended periods of light sleep that last a few seconds or several minutes. You may just lose attention and stare blankly or even close your eyes and your head might snap up.

Microsleeps are dangerous when driving. During a 4 second microsleep a car travelling at 100km/h will travel 111 metres while completely out of the drivers control.

Microsleeps usually occur at times when you would normally be asleep or when you are tired and trying to stay awake.

How to avoid fatigue

• Get enough quality sleep before you begin driving. Be sure to have 7 to 8 hours of uninterrupted sleep before your trip.
• The worst time to begin your trip is after work. You will be tired already even though you do not realise it.
• Aim not to travel more than 8 to 10 hours each day.
• Take regular 15 minute breaks at least every two hours. Get out of the car, get some fresh air and some exercise.
• If possible share the driving. Get your passengers to tell you if you look tired or if you are showing signs of tiredness.
• Eat well balanced meals at your usual meal times. Avoid fatty foods which can make you feel drowsy.
• Avoid alcohol and medicines that can cause drowsiness.
• Avoid driving at night. The chances of crashing are much higher late at night and early morning.

Will coffee, fresh air or loud music cure fatigue?

In the short term coffee may be of some benefit but its effects wear off and you are likely to suffer from sleep rebound putting you at risk of crashing. Playing music and fresh air will only have a short-term benefit in keeping you alert.

The only cure for fatigue is sleep.

More information

Heavy vehicle fatigue laws