Research commissioned by the Government found that falling asleep at the wheel accounts for up to 20% of accidents on motorways or similar roads, and as many as one in ten of all crashes on Britain's roads. 

Sleep-related vehicle accidents are more likely to result in serious injury than the 'average' road accident because a sleeping driver does not react before a crash. 

The greatest risk of falling asleep at the wheel is between midnight and 6am. 

It can affect any driver, but people who drive as part of their job may be more at risk. Research has found that people driving company cars fall asleep at the wheel more often, and are more likely to be involved in accidents than private car drivers.

Alcohol and drugs (including some medicines) can make you more tired without you realising it. 

Body clock

Driving between midnight and 6am presents a particular risk for sleep-related vehicle accidents, as this is when your 'body clock' is in a natural trough. There is another, smaller trough between about 2.00pm and 4.00pm. 

All sleepy drivers are aware of their tiredness, particularly when they reach the stage of 'fighting sleep' (i.e. doing things to keep themselves awake, such as winding down the window). You don't fall asleep without warning. 

Opening the window for cold air or turning up the radio are of very limited benefit and sufficient only to find a safe place for a break. 

Reaction time devices are of little practical use in detecting driver tiredness. By the time they work a driver is already well on the way to falling asleep. 

Top tips

• Plan your journey to include a 15-minute break every two hours on a long journey
• Take a short nap and resume the journey 15-20 minutes later 
• Avoid making long trips between midnight and 6am when natural alertness is low 
• Remember the risks if you have to get up unusually early to start your trip, or have a long drive home after a full day's work 
• Find a safe place to stop if you begin to feel drowsy (not the hard shoulder) 
• Opening the window or turning up the radio does little to prevent a driver from falling asleep at the wheel 
• Drink two cups of coffee or a high caffeine drink, and then take a short nap to allow the caffeine to kick in