Driving the day after a heavy drinking session can be just as dangerous as getting behind the wheel drunk, research has revealed.
The Dutch study, presented to an Australasian drug and alcohol conference this week, found the risk of driving hungover was even greater than that of driving at the rate of the new blood alcohol limit coming into effect next year.
As part of the Utrecht University study, nearly 50 healthy volunteers underwent simulated highway driving tests the night after a drinking session averaging about 10 alcoholic drinks.
Compared to the same tests after a night of not drinking, the results showed a hangover could significantly increase the number of lapses in attention and weaving.
The tests were performed after the participants' blood alcohol concentration (BAC) had returned to zero.
Study author Dr Joris Verster said the magnitude of driving impairment was higher than that observed with a BAC of 0.05 per cent, which will become the legal New Zealand limit for adult drivers from next year when the amount is lowered from 0.08 per cent.
"People should be alerted to the potential risks of driving during the hangover state."
In a smaller UK study, participants undertook a 20-minute simulation of driving in a mixed urban and rural setting with hazards such as pedestrians.
It showed major increases in speed variability, reaction time and driving errors.
Professor Chris Alford, from the University of the West of England, said the findings that driving performance was adversely affected by hangovers should be incorporated into driver safety campaigns.
But University of Canterbury lecturer Dr Eric Crampton, who has been researching the issue, wasn't alarmed at the findings. "I would expect that driving while suffering from a very bad cold and headache, or driving with the flu, or being pretty tired, would have a similar effect."