Rotorua parents are dropping their kids at school the morning after a boozy night, not realising they are still over the limit, a local road cop says.
Research has revealed driving the day after a heavy drinking session can be just as dangerous as getting behind the wheel drunk.
The Dutch study, presented to an Australasian drug and alcohol conference recently, found the risk of driving hungover was even greater than that of driving at the new blood alcohol limit, coming into effect next year.
Bay of Plenty road policing manager Inspector Kevin Taylor said most hungover drivers were still drunk from the night before.
"If you have a big night on the booze and think that having three or four hours' sleep is going to fix it ... when you wake up in the morning you're still going to be over the limit and still going to be affected.
"Sadly, anecdotally from around the districts over the last year or so, we even see parents dropping kids at school who are in that position."
With holidays approaching, people needed to be extra vigilant, Mr Taylor said.
"When people switch to holiday mode and school's out and work is finished, the laws of physics don't take a holiday. The world keeps rotating on its axis ... we need to keep our brains plugged in and drive accordingly."
However, Rotorua Principals' Association co-president and Otonga School principal Linda Woon said she had never heard of parents dropping off kids at school while under the influence of alcohol. She said if staff saw people driving erratically outside her school they would report it. Staff were very conscious of the safety of their students.
She said drivers had been seen driving on the footpath, performing U-turns on the pedestrian crossing and "blatting" along Otonga Rd at times when school children were either arriving at school or leaving and that had been reported to police.
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 with 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.
Tests were performed after the participants' blood alcohol concentration had returned to zero.
Study author Dr Joris Verster said the magnitude of driving impairment was higher than that observed with 50mg of alcohol per 100ml of blood, which will become the legal New Zealand limit for adult drivers from next year when the limit is lowered from 80mg.