Under legislation passed this year, the legal alcohol limit for drivers aged 20 and over will be lowered from 80 to 50mg of alcohol per 100ml of blood, or 400 to 250 micrograms of alcohol per litre of breath.
Drivers whose breath registers between 251 and 400mg of alcohol will receive a $200 fine, and those who have more booze on their breath will still face criminal sanctions.
The alcohol limit for drivers under the age of 20 will remain at zero.
Cliff said there would be no grace period.
"We've been handing out brochures to drivers for weeks and weeks, there's been lots of advertising. We've been pushing the Safer Summer message everywhere and NZTA have got advertising on all the bus stop signs.
"It's just been so well publicised," he said.
"The really good thing is, when the Government announced this about 12 months ago we saw the number of prosecutions [for drink driving] plummet, so we think the vast majority of people have got the message already."
Cliff estimated the number of drink-driving offences would not change, although many would be for lower-level infringements.
"What we expect to happen is, based on the Australian experience, it pulls down drinking across the whole population."
He said police would be out in numbers enforcing the new rules as part of their Safer Summer campaign, which also had a strong focus on speed.
In New Zealand there are an average of 61 fatalities, 244 serious injuries, and 761 minor injuries every year caused by drivers who have been drinking.
Cliff said the new rules brought New Zealand up-to-date with most other countries.
"There's a couple of jurisdictions that are still in the stone ages - the United States and the UK - but Australia went down, and a lot of European jurisdictions have gone even lower so we're definitely lining up with the better-performing countries now."
Nonetheless, drivers at the new alcohol limit were still six times more likely to be involved in a crash compared with sober drivers, Cliff said.
There was no safe amount of alcohol for driving and it was always recommended that drivers not drink at all, he said.
On Thursday a woman blew nearly four times over the legal alcohol limit in Hamilton after she crashed into a road sign.