From Monday, the limit for drivers over 20 lowers from 400mcg of alcohol per litre of breath to 250mcg, and from 80mg of alcohol per 100ml of blood to 50mg.
The change will see fewer deaths and serious injuries on New Zealand's roads, Dunedin road policing manager Senior Sergeant Phil McDouall says.
Those recorded at 251-400mcg of alcohol per litre of breath will receive a $200 infringement notice and 50 demerit points.
National road policing manager Superintendent Carey Griffiths said the lower limit would have a ''strong deterrent effect'' on drink drivers.
''There is no 'safe' level of alcohol for driving, and the best advice is to avoid any doubt by choosing not to drive if you are going to drink,'' he said.
''Call a taxi, take a bus or get someone who hasn't been drinking to drive you home. Think ahead, it's always easier if you have a plan.''
Snr Sgt McDouall agreed and said Southern police would be on the road in force from December 1.
''From December 1 it starts and if you are over, you're over. There's no discretion, you get a ticket,'' he said.
The change in limit would see a change in drinking culture, he said.
''People think they can drink and drive safely, but now if they are over the limit they face a fine. Alcohol does affect people, there's no doubt about it.''
Dunedin City Council planning and regulatory committee chairman Cr David Benson-Pope said the council was pleased with the change.
''Any police attention to greater road safety in the city is most welcome.
''We have a wonderful lifestyle now and increased safety on the roads can only further improve that.''
Hospitality Association of New Zealand Otago branch president Mark Scully said while the association was supportive of measures to kerb drink-driving, the law change could have unintended consequences for Dunedin restaurants and bars.
''It's not about people having a session, it's about having a beer after a meeting or work, but now people will err on the side of caution [and not drink].''
''Some people won't come [into bars and restaurants] at all and for some their consumption will half.''
The law might end up targeting the wrong people, he said.
''I don't believe the damage in New Zealand is being done by the lady having a wine or two.
''You can legislate all you like but the guy having a skin-full and driving hasn't changed; he's still going to drive.''
Among those who continued to enjoy a post-work tipple or drink with their meal, low alcohol beverages might become the norm, he said.
Inch Bar owner Jonas Hjertquist said he had already bought 2.5% alcohol beer in anticipation of the change in behaviour.
''People haven't come to me and said `can I have a low-alcohol beer', but now there's going to be a change in behaviour,'' he said.
He had long offered a 3.7%-alcohol beer, but the new option was aimed at luring punters in what had become an increasingly difficult industry.
''The biggest worry from the entire industry is this is going to provide another excuse for people to stay at home and drink cheap alcohol from supermarkets,'' Mr Hjertquist said.
''I believe the law can be a blunt instrument with which to deal with bad driving.''
Emerson's Brewery general manager Bob King said it was too early to know what effect the law change would have.
''We are just really seeing how the landscape evolves because there's two schools of thought,'' he said.
''One saying people will drink lower alcohol and the other's saying people will drink less.''
He suspected it might be the latter because of brand loyalty, however, he was ''pretty relaxed'' about the law change and was taking a ''wait and see approach''.
New Zealanders would always drink in social environments, but their behaviour might change.
''We like to be social and interact with people and it would be a shame to lose sociability as part of our culture and lifestyle.''
