In the road transport and driving communities, 'driver fatigue' is often used as an umbrella term for drivers needing sleep. However, there are important distinctions between sleepiness and fatigue which could be helpful to fleet managers. 

Medically, fatigue tends to denote a persistent lack of energy, but all of us recognise that point that we are finding it harder and harder to continue doing something. When driving, or doing any repetitive task, it's useful to think of fatigue as the point at which the brain becomes tired and disengaged or unresponsive to the task. Typically, we will become less precise, have poorer response times, and start to make mistakes or be clumsy. This kind of fatigue or tiredness can be caused by prolonged work periods or boredom. 

This kind of fatigue is common in bus drivers, who drive very familiar routes, and is associated with repetitive tasks, such as may be experienced by final mile delivery drivers who travel relatively short distances before stopping, parking, delivering and driving again. 

Studies suggest that drivers start to make significantly more mistakes after two hours of continuous driving. 

When we ask the brain to do the same thing again and again – whether adding numbers or scanning for parking spaces – its internal highways become congested. A process of 'competitive inhibition' effectively blocks that ability for a little while for the congestion to disperse. 

If drivers feel fatigued in this way, they should take a break, move about, have a drink and a conversation. A sleep would create that sort of 'break' but, unlike for sleepiness which only sleeping cures, a nap is not necessary. Exercise and social interaction both boost hypocretin, a neuropeptide which increases alertness. It also gives their brain's network a chance to clear so it can function well again. 

What to do 

• Examine shift patterns to see whether longer periods of driving can be broken up. 

• Educate drivers about the need for breaks to allow their brain and body to reset. 

• Educate drivers about the need for breaks to include movement, hydration and social interaction, wherever possible. 

• Collect and analyse data which might uncover whether task-fatigue may be a problem – and act on it.