Sleep-deprived drivers are less alert than those who have drunk more than the legal limit of alcohol, according to new research.
A study published today in the journal Occupational and Environmental Medicine found that fatigue can reach dangerous levels at a much earlier stage than has been assumed.
The authors, from Australia and New Zealand, tested responses of 39 volunteers after sleep deprivation and after drinking alcohol equivalent to the legal driving limit in Scandinavia.
They found that those who had been up since 6am performed worse in tests between 10.30pm and midnight than those who were
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tested in the morning with 50mg of alcohol in their bloodstream (the UK limit is 80mg).
The researchers suggest that countries which set drink-driving limits should consider setting restrictions to prevent people who have been awake for more than 18 hours from driving, piloting aircraft, or operating machinery. Tiredness is estimated to play a part in between 16% and 60% of road accidents in the United States, they say, but few attempts have been made to work out at what point in the day or night that tiredness reaches serious levels.
“The implications of fatigue for safe performance are well recognised particularly in road safety, but in other settings as
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well,” write Andrew Williamson of the School of Psychology University of New South Wales, and Anne-Marie Feyer from the University of Otago, Dunedin.
The volunteers - lorry drivers and members of the transport corps of the Australian army - were put through tests to measure thinking speed and physical reactions, coordination and attention span. They carried out the tests after a day and night of wakefulness and after drinking alcohol.
The researchers found that commonly experienced levels of sleep deprivation - staying awake for 17 to 19 hours - depressed performance in the same way as drinking a couple of glasses of alcohol.
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