A zero alcohol limit for teenage drivers is now being enforced. The limit changed at midnight on Saturday.
It means drivers under 20 years old can no longer drink any alcohol before getting behind the wheel.
Those caught with a blood alcohol level between zero and 0.03% will be fined $200 and given 50 demerit points. Those with a higher level will face existing penalties.
The Government expects the zero limit regime will save many lives.
Last year, there were 60 deaths involving 15 to 19-year-old drivers.
The Students Against Driving Drunk group says it is thrilled with the new law.
Chief executive Anna Reid says it will reduce the amount of harm and save a lot of lives in the long run.