One in five drivers (20%) has risked getting behind the wheel the morning after a night of heavy drinking even though they thought they could still be over the limit, according to research.
A poll of almost 20,000 motorists commissioned by the AA found 29% of 25 to 34-year-olds admitted to drinking and driving the following morning.
Some 62% of drink-drivers killed in crashes in England and Wales are males aged between 17 and 34, Department for Transport figures show.
AA president Edmund King warned that sleeping, drinking coffee or having a cold shower do not help to sober people up.
He said: "Everyone's body reacts differently to alcohol, so it will take differing lengths of time for it to clear your system.
"The only way you can be sure of not falling foul of the law the morning after is to limit your drinking or not drink at all.
"However, if you do want to drink and are unsure whether you would be over the limit, it is best not to drive or at least use a self-breathalyser to indicate how your body is coping the morning after."
The Scottish Government reduced the alcohol limit for drivers from 80mg to 50mg per 100ml of blood in December 2014, but the legal level in England and Wales remains at 80mg.
A recent survey of 1,000 drivers by road safety charity Brake and insurance firm Direct Line found that 78% think the drink-drive limit is too high.
More than half (54%) of respondents believed the limit should be slashed to an effective zero tolerance of 20mg per 100ml of blood.