In this fact page we cover:

  • Risks associated with driving when tired
  • Causes of fatigue
  • Ways to reduce the risk of driving when tired

Fatigue is a major cause of road crashes in the UK

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Police statistics show that fatigue contributes to about 4% of fatal road crashes and 2% of all collisions in Britain. However, it is likely that the true figures are far higher because fatigue is hard to spot and, unlike alcohol and drugs, police can’t test for tiredness. Worldwide, it is estimated that between 10% and 20% of all road crashes are fatigue-related.

Most sleep-related crashes happen on motorways and dual-carriageways, probably because of the monotonous road environment and lack of driver stimulation.

Research suggests driving when tired can be as dangerous as drink-driving.

Crashes typically involve vehicles running off the road or into the back of another vehicle. They tend to happen at high speeds, because drivers do not brake before crashing, so the risk of death or serious injury is high.

Factors that contribute to driver fatigue

Many factors can contribute to driver tiredness and increase the risk of being involved in a fatigue related crash. These include:

Lack of sleep or disturbed sleep: This could be due to disruptions in life such as a new baby, busy schedules or stress, or could be due to sleep disorders such as narcolepsy, insomnia or sleep apnoea.

Time of day: The most common times for drivers with normal sleep patterns to fall asleep at the wheel are early morning (2am-6am) and early afternoon (2pm-4pm). These times are when the body clock reaches a natural dip, causing drowsiness and reduced concentration.

Stress: Tiredness and difficulty concentrating are typical symptoms of stress.

Irregular sleep patterns: This can be a problem caused by irregular work shifts and switching from day to night shifts without having sufficient time off in between for your body clock to adjust. Research has found shift workers are particularly high risk for sleep-related crashes.

Driving for long periods: Research has found driving deteriorates after two hours of continuous driving, as you become less able to concentrate, and slower to react to hazards. The longer you drive, the more rest you need to recover driving performance. Breaks are therefore recommended every two hours.

Vehicle engineering: Modern vehicles are usually quiet and comfortable for the driver, meaning a more relaxed drive. This can lull drivers, particularly in vehicles fitted with comfort-enhancing features such as cruise control.

Medication: Some prescription and over-the-counter drugs can cause drowsiness. Medications may carry warnings that are not clear they impair driving, for example small print that only advises not to operate heavy machinery.


Signs of fatigue

Fatigue does not occur without warning, and most people recognise the symptoms but many still underestimate the dangers of continuing to drive while tired.

Warning signs include:

  • increased difficulty concentrating
  • yawning
  • heavy eyelids
  • eyes starting to ‘roll’.

By the time your head starts nodding, you could be having a 'microsleep' (see below).

If you nod off while driving at 70mph, you could travel 200 metres without knowing it Down arrow icon to open accordion

A ‘microsleep’ occurs when someone nods off for between two and 30 seconds without realising or remembering it, often known as head-nodding. This occurs when people are tired but trying to stay awake, most common in monotonous situations, like motorway driving at night. A Brake and Direct Line survey found one in three (31%) of UK drivers surveyed admit having experienced a microsleep at the wheel.

After a microsleep a driver may feel like they’ve just briefly nodded their head, but they have actually been asleep. During this time, they will have been completely unaware of the road and unable to control their vehicle. In six seconds, a vehicle being driven at 70mph travels about 200 metres, which is enough time to veer across three lanes of traffic or into the central reservation. Simulator studies have shown a clear relationship between microsleeps and crashes.


Who is most at risk of driver fatigue?

At-work drivers are particularly at risk from tiredness, because they typically spend longer hours at the wheel, with four in ten tiredness-related crashes involving someone driving a commercial vehicle.

Male drivers are more likely to experience sleep-related crashes than females. Drivers under 30 are at higher risk than older drivers, and are most likely to crash due to tiredness in the early morning after little or no sleep.


Driver fatigue and the law

It's hard to prove that a crash was caused by driver fatigue. It is not possible to test drivers for tiredness and a driver who crashed may not admit to driving while tired.

If police suspect tiredness they can investigate length of driving, lifestyle (did the driver sleep for an adequate time before driving) and the type of impact (many tiredness crashes are high speed and do not involve braking because the driver is asleep). Lack of skid marks from braking, information from event data recorders and eye witness statements can all help to identify fatigue as contributing to a road crash.

A tired driver who kills someone can be charged with death by dangerous driving or death by careless driving. The maximum penalty for death by dangerous driving is a prison sentence of 14 years.

Organisations that operate fleets of vehicles have a legal duty of care to “ensure, so far as is reasonably practicable, the health and safety of all employees while at work” and are responsible for what might happen if this is not done.

Commercial vehicle legislation Down arrow icon to open accordion

Anyone who employs people who drive for work must put in place all reasonably practical measures to manage driver fatigue. Employers need to assess which drivers and journeys are at risk and set schedules that do not require drivers to exceed recommended working limits and driver hours.

Professional drivers of goods and passenger road vehicles must comply with UK and EU legislation, maintain log books, record hours of work and rest and ensure medical assessments are up-to-date. Many commercial vehicles use event data recorders (telematics devices), which can be studied by police if the vehicle is involved in a crash.

In most cases, bus and truck drivers are bound by EU driver hours regulations, which limit time at the wheel to nine hours a day or 56 hours a week if all or part of the journey is in more than one EU country. Drivers must take a break after 4.5 hours of driving and they must have unbroken rest periods.

Other vehicles, including vans and some minibuses, are bound by less rigorous domestic rules, which allow longer driving hours and shorter rest periods.

Medical restrictions Down arrow icon to open accordion

If you have a medical condition associated with fatigue that can be treated (e.g. sleep apnoea), you should inform the DVLA of your condition and seek treatment.

If you have a fatigue-related condition which cannot be treated, e.g. narcolepsy, you must contact the DVLA on diagnosis to relinquish your licence.

Your doctor is legally required to instruct you to do this, and must also inform the DVLA if they discover you are continuing to drive.

A driver who fails to notify the DVLA can be fined £1,000 or could face prosecution.

Vehicle technology and good road design can help prevent road crashes due to fatigue or reduce the likelihood of death or serious injury if a crash does happen.

Driver distraction and drowsiness recognition technology can detect symptoms of fatigue and alert the driver, warning them to take a break. Different systems can monitor head and eye movements, heart rate and brain function, as well as steering and braking patterns that indicate a driver is not paying attention to the road.
References and further reading Down arrow icon to open accordion