There are a number of causes of fatigue.

Sleep factors

• Getting less sleep than you need
  Not getting enough sleep before your first shift or between shifts will increase the chance of fatigue.
• Lack of sleep over a number of days
  Lack of sleep can build up over a number of days – this is called ‘sleep debt’. The more sleep debt you accumulate, the quicker you become fatigued on a long haul. As a result, you’re more likely to become fatigued during a shift at the end of the week, than a shift at the beginning of the week.

Work factors

• Long driving hours
  Long work hours, especially over more than one day, can lead to fatigue.
• Night time driving
  Driving at night can put extra stress on your body, as this is usually when you’re ready to sleep.
• Irregular hours and early starting times
  Rosters that make it hard to get enough refreshing quality sleep can lead to fatigue.
• Tight scheduling
  Stressful work with tight schedules contribute to fatigue.
• Insufficient time to recover
  Fatigue can also be caused by not having enough time to rest and recover between shifts.
• Doing non-driving physical work
  Work such as loading and unloading, as well as heavy lifting can add to the onset of fatigue.
• Poor driving conditions
  Some of the following conditions can also affect your concentration and therefore make driving more difficult.
  • hot weather (hot & stuffy in the cabin)
  • wet weather
  • noise
  • monotonous driving
  • driving on very familiar roads  

Time of day factors 

• Working when you should normally be asleep
  There are times of day when your body wants to rest or be asleep (such as in the early hours of the morning). This is because our bodies are programmed to operate on a 24-hour cycle.
  
  When the sun goes down, your body reacts by preparing for sleep. After midnight, your ‘body clock’ automatically starts to reduce your body temperature as well as your physical alertness so that you can sleep.
  
  The other time when your body wants to sleep is ‘siesta’ time in the early afternoon after lunch.
  
  These are particular danger times for fatigue and especially microsleeps.
• Trying to sleep during the day
  Your programmed ‘body clock’ is a key reason as to why it can be harder to sleep during the day than at night. When the sun is out, daylight signals to your body to be more alert and awake. Trying to rest during this time means sleep is less refreshing for the body.

Physical factors

• Poor health and fitness
  Being unfit or overweight can mean that driving is more draining. Other conditions such as diabetes, if they are not treated, can also make you feel tired and fatigued.
• Emotional issues
  Stress can affect you in many ways, one of which is the ability to cause your body to become fatigued more quickly.
• Sleep disorders
  Some people suffer from sleep disorders such as ‘sleep apnoea’. This is where breathing stops and starts during sleep, causing sleep to be less refreshing than it normally would be. If you snore loudly, wake up still tired, fall asleep unexpectedly, or your partner notices you stop breathing during the night - you may have sleep apnoea. If you think you are suffering from sleep apnoea, see your doctor for advice.