Hungover motorists drive 10mph faster and are four times more dangerous than a sober driver, according to new research.
The study by Brunel University, commissioned by RSA, found that a poor night's sleep, low blood sugar and dehydration, all brought on by alcohol, affect the ability to drive safely even if someone is under the drink-drive limit.
Eleven students were tested on a driving simulator while sober and again while suffering a hangover.
The tests showed that hungover drivers drove 10mph faster, left their lane four times more often and committed double the number of traffic violations.
Graham Johnston, RSA's underwriting director of commercial motors, said: "What surprised us was that people were driving faster. The fact they were driving more erratically we'd expect. Not taking care, going through red lights, that's more alarming.
"It's as if they are in a daze, thinking 'I have to get to work. I'll get there as fast as I can and take an Alka Seltzer to feel better when I get there'."
Mr Johnston has advised firms that they should provide transport to work the morning after the Christmas party to avoid dangerous driving.
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