The morning after your Christmas party might be your downfall under new drink drive laws.
The new limits will add a couple of hours to your sobering-up time, warns an emergency department specialist, meaning you could still be over the limit as late as mid-morning.
And women are particularly at risk of falling foul of the law, says clinical toxicologist Dr Paul Quigley.
"Even if females stop drinking at 1am and then go to bed and sleep they will still be over the legal limit at 10am. Under the old drink-driving levels they would just squeak under at 8am."
The legal alcohol count for drivers aged 20 and over was lowered from 80mg to 50mg of alcohol per 100ml of blood, or 250 micrograms of alcohol per litre of breath (previously 400) on December 1.
Quigley expects more people will be ticketed by police in the mornings as stricter levels mean on average it will take men about an extra hour to fall below the new alcohol limit the next day, and up to two hours for women. "This will be a particular issue for people in the 18-25 age group who go out drinking on a Thursday or Friday night and get up early to go to work," he said.
"Sleep does not speed up being sober ... our livers simply chug their way through one standard drink per hour, awake or asleep.
"Sleep may make you feel better, because when you wake you are less drunk and more energetic, but in fact you are still impaired for driving."
Research by Quigley on how the new limits will impact on motorists will be sober reading for some drivers.
Using a case study of someone who consumed 13 standard drinks between 5pm and midnight, and then went to bed, under the old regime, men would generally be fit to get behind the wheel about 5.30am. But that would now stretch out to about 6.30am.
Women would have passed a breath test about 8am under the previous breath limits, but that would change to about 10am under the new rules.
Police expect to issue 19,000 additional tickets in the first year of the new regime, potentially netting $3.8 million.
Adult drivers blowing between 251 and 400 will not face court action but will receive a $200 infringement fee and 50 demerit points on their licence. If a driver is caught a second time he or she risks three months without a licence. Police warn they will be out in force in the mornings during the festive season and insist there will be no leniency for motorists who plead ignorance of the new rules.
"There is a real risk people have a skinful at night and believe they will be fine after a few hours sleep or by laying off it for a bit," said Dave Cliff, assistant commissioner for road policing.
"What these drivers have to consider is that not only are they a danger to other people but there could be serious consequences for themselves, too. If people are going to have more than a few drinks they should plan not to drive the next morning."