1.5 Driver Fatigue
Driver fatigue (driving when you are tired) is a major road safety hazard. Fatigue
related crashes tend to be severe because sleepy drivers don’t take evasive action.
The risk of serious injury to a driver, passengers or the occupants of other vehicles in
this type of crash is very high.
1.5.1 What is driver fatigue?
Fatigue is a common term that refers to mental and physical tiredness. Fatigue causes
loss of alertness, drowsiness, poor judgement, slower reactions, reduced driving skill and
may cause you to fall asleep at the wheel.
If you are a driver and you become drowsy, you can drift into ‘micro-sleep’, which is a
brief nap that lasts for around three to five seconds. At 100km per hour your vehicle
can travel over 100 metres in that time, which is enough time for it to run off the road into
a tree, another vehicle or a pedestrian.
1.5.2 The main causes of fatigue
Body Clock Factors
Your body runs on a natural biological cycle of 24-26 hours – often called your
‘body clock’. Your body clock programs you to sleep at night and to stay awake during
the day.
Your body clock is controlled partly by light and dark and partly by what you do. If you
normally work from 9am to 5pm, some of the things that happen to you as a result of
your body clock are:
n the morning light tells your body clock to make you more alert
(wakes you up);
n during the morning your body clock keeps you alert;
n after lunch, your body clock will turn your alertness down for a couple of
hours;
n your body clock will make you most alert and aware in the late afternoon and
early evening;
n darkness in the evening tells your body clock to turn your alertness down
again so you can get ready to sleep; and
n after midnight your body clock will turn your alertness right down so that you
are ‘switched off’ between 2am and 6am. At this time all your body functions
are at their lowest level.