Health experts are backing a government proposal to cut the blood alcohol limit, saying people driving within the current level may be slurring their speech and falling over.
The Government released its 10-year road safety strategy, "Safer Journeys" last August.
It proposed reducing the legal blood alcohol limit from 80mg per 100ml to 50mg per 100ml. There could also be a zero blood alcohol limit for those under 20 years of age and recidivist offenders.
Transport Minister Steven Joyce was progressing a road safety Cabinet paper on the impacts of alcohol out of Safer Journeys. Final Cabinet consideration on it was due shortly, a spokeswoman from his office said.
Capital Coast District Health Board chief medical officer Geoff Robinson said the 80mg level was reasonably high by international standards.
At that level people would be perceived as intoxicated with slurrying speech, unsteady walking, impaired judgement, nausea and tripping over, he said.
"People at 80mg/l are quite significantly intoxicated but I think that because 80mg/l is the legal driving limit they think it's ok."
A man weighing 85kg and measuring 1.8m can consume between five to eight standard drinks, or seven stubbies of beer, over a two-hour period and remain below the current limit, ESR forensic toxicologist Allan Stowell calculated.
An average woman weighing 70kg and measuring 1.65m could consume 3.4-5.4 standard drinks in a two-hour period.
"I'm not saying they'd be safe drivers, but they would probably not exceed the limit."
Increasing the time spent drinking meant more drinks could be consumed before reaching the current 80mg/l limit, Dr Stowell said.
Reducing the limit to 50mg/l would see the limit of standard drinks over two hours down to 3.6-5.9 for men and 2.4-4 for women.
Men and women have the same rate of clearing alcohol from their bodies but women do not need to drink the same amount as men to achieve the same blood alcohol level, Dr Stowell said. That accounts for the difference between the sexes in the numbers of drinks which can be consumed.
He said 50mg/l was an internationally recognised threshold above which the risk of being involved in an accident increased.
University of Otago head of preventive and social medicine Jennie Connor said a small difference in the blood alcohol level of drivers could result in a large increase in the risk of them crashing.
International research showed reducing the legal blood alcohol limit not only reduced the number of alcohol-related accidents but also the number of people caught with random breath testing and led to a change in public attitude.
With a lower level people were more likely to keep track of how much they were drinking and to decide earlier in the night whether they would drive, Prof Connor said.
A study in Denmark showed more people decided not to drink at all, or to have only one drink, when they were driving.
It was also shown to reduce problem drinking in general through increased awareness, she said.
The United Kingdom, the United States and Canada still have a 80mg/l limit. The majority of countries, including Australia, Austria, Belgium, France, Germany, Italy, and the Netherlands, have a 50mg/l limit.
There are others, Poland (30mg/l) and Norway, Russia and Sweden (all 20mg/l) who have even lower limits, Prof Connor said.
The comments came as the Alcohol Advisory Council (Alac) launched a new drinking campaign last night aimed at the friends and loved ones of problem drinkers.
Alac chief executive Gerard Vaughan said the advertising aimed to create an environment where people could have the confidence, social permission and tools to talk to a close friend or family member if they wanted to.