Alcohol interlocks in NZ: what NZTA's own numbers show
Most people have never seen an alcohol interlock. If you are convicted of a serious drink driving offence in New Zealand, you are likely to get very familiar with one.
We asked NZ Transport Agency Waka Kotahi (NZTA) for its data on drink driving and alcohol interlocks under the Official Information Act. NZTA declined most of the request, saying it would need substantial collation and research, but it did release an analysis of the Driver Licence Register that it had prepared for the Ministry of Transport in May 2025 [1]. This article goes through what that analysis shows.
What an interlock is, and who gets one
An alcohol interlock is a breath testing device fitted to your vehicle. You blow into it before the engine will start, and it asks for further samples at random while you drive [3].
A court must impose an alcohol interlock sentence if you are convicted of a qualifying drink driving offence with a breath reading of 800 micrograms or more (or a blood reading of 160 milligrams or more), or if you have a previous qualifying conviction for an offence committed within 5 years [2]. There are limited exceptions, but for most people in those situations the interlock is not optional.
Interlock sentences have been available to the courts since September 2012, and became mandatory in sentencing for serious driving offences involving alcohol from 1 July 2018 [1].
The numbers, year by year
One thing to be clear on: the interlock sentence comes from the court, and for serious offending it is mandatory [2]. The figures below count drivers sentenced to an alcohol interlock, from NZTA's Driver Licence Register [1].
This is the number of drivers sentenced to an alcohol interlock each year, straight from NZTA's analysis [1]:
| Year | Drivers sentenced to an interlock |
|---|---|
| 2012 | 1 |
| 2013 | 145 |
| 2014 | 217 |
| 2015 | 224 |
| 2016 | 307 |
| 2017 | 258 |
| 2018 | 925 |
| 2019 | 2,539 |
| 2020 | 2,474 |
| 2021 | 3,013 |
| 2022 | 3,079 |
| 2023 | 3,296 |
| 2024 | 3,585 |
- COVID-19 rules in place: 28 February 2020 (first case) to 12 September 2022 (traffic lights ended, most rules removed from 13 September 2022)
- Lockdown 1: Alert Level 4 nationwide: 25 March 2020 to 27 April 2020
- Lockdown 2: Alert Level 4: 17 August 2021 nationwide; outside Auckland ended 31 August 2021, Auckland ended 21 September 2021 (Auckland then stayed at Level 3 until 2 December 2021)
- Interlocks mandatory: From 1 July 2018 alcohol interlocks became mandatory in sentencing for serious driving offences involving alcohol [1]
A few things jump out.
- The 2018 law change is obvious in the numbers. In 2017, 258 drivers were sentenced to an interlock. In 2019, the first full year after interlocks became mandatory for serious offending, it was 2,539. That is almost ten times as many [1].
- The numbers have kept climbing. 2024 was the highest year on record at 3,585, about 41% more than 2019 [1].
- It is a big group of people. Between 2012 and the end of 2024, NZTA counted 20,063 interlock sentences, covering 18,588 different people [1].
Some people were sentenced to an interlock more than once in the same calendar year, which is why the number of sentences is slightly higher than the number of people. In 2024, 28 people accounted for 56 sentences that way [1].
How long people stay on the interlock
The law sets the minimum. After at least 12 months on an interlock licence, and with a clean record for the previous 6 months (or 3 months if you have been assessed as fit to drive), you can apply for a zero alcohol licence [2]. The zero alcohol licence then lasts 3 years, and your limit during that time is zero [2].
NZTA's data shows how that plays out in practice. Of the 18,588 people sentenced to an interlock, 11,215 had moved on to a zero alcohol licence by 29 May 2025. That is about 60% [1]. The data does not break down what happened to the other 7,373 people, so we will not guess. Some will simply still have been on their interlock when the data was pulled.
For people sentenced to an interlock once, from 1 July 2018 onwards, and later moved to a zero alcohol licence, this is how long it took [1]:
| Time from interlock licence to zero alcohol licence | People | Share |
|---|---|---|
| Less than 18 months | 6,805 | 68% |
| 18 months to less than 2 years | 1,732 | 17% |
| 2 years to less than 3 years | 1,038 | 10% |
| 3 years to less than 4 years | 291 | 3% |
| 4 years or more | 141 | 1% |
So roughly two in three got through in under 18 months, which lines up with the 12 month minimum plus the clean period the law requires [1][2]. But about one in seven took 2 years or longer [1].
NZTA points out that the time is measured from the start of the interlock licence to the start of the zero alcohol licence, and does not allow for any gaps when an interlock licence was not actually held, for example after a further conviction or if the licence expired [1].
What this means if you are facing an interlock
If you have been told an interlock sentence is likely, the numbers give you a realistic picture:
- Plan for more than a year. The legal minimum is 12 months on the interlock, and most people take between 12 and 18 months [1][2].
- Then plan for 3 more years at zero. The zero alcohol licence that follows lasts 3 years [2]. A single drink before driving during that time is an offence.
- The clean period matters. You need a clean record for the months before you apply for the zero alcohol licence, so a slip late in the interlock period can push your exit date out [2].
Where a limited licence fits
People often ask whether a limited licence (work licence) is an option instead. If you are subject to an alcohol interlock sentence, you cannot apply for a limited licence, and the same applies if you would have been subject to one but an exception applied [2]. For those drivers, the interlock licence is the legal route back onto the road.
Some first-time drink drivers with lower readings may be eligible for a limited licence. NZ Limited Licence prepares limited licence application documents. We are not lawyers, we do not appear in court, and the decision is always the judge's. Phone 0800 437 005.
For what happens from the roadside breath test onwards, see Blew over the limit in NZ? What actually happens next.
Sources
- NZ Transport Agency Waka Kotahi, response to Official Information Act requests OIA-23159 and OIA-23285 (2 September 2026), Attachment 1: Driver Licence Register analysis of alcohol interlock and zero alcohol licences prepared for the Ministry of Transport (report date 30 May 2025). Released to NZ Limited Licence; not published online.
- Land Transport Act 1998 (version as at 4 September 2026), sections 65AB, 65AC, 65AE, 65AG and 103, New Zealand Legislation, https://www.legislation.govt.nz/act/public/1998/0110/latest/whole.html (accessed 27 September 2026)
- Alcohol interlocks, Govt.nz, https://www.govt.nz/browse/transport/driving-fines-and-penalties/alcohol-interlocks/ (accessed 27 September 2026)
- History of the COVID-19 Alert System, Unite against COVID-19 (New Zealand Government), https://covid19.govt.nz/about-our-covid-19-response/history-of-the-covid-19-alert-system/ (page last updated 29 June 2022; site since retired, archived copy at web.archive.org accessed 27 September 2026)
- The next phase of our COVID-19 response, Unite against COVID-19 (New Zealand Government), covid19.govt.nz (page last updated 23 September 2022; site since retired, archived copy at web.archive.org accessed 27 September 2026)
Frequently asked questions
How many drivers are sentenced to an alcohol interlock in New Zealand each year?
NZTA's data shows 3,585 drivers were sentenced to an interlock in 2024, the highest year on record, up from 258 in 2017.
How long do you have to stay on an alcohol interlock?
The legal minimum is 12 months, with a clean record for the last 6 months (or 3 months if assessed as fit to drive) before you can apply for a zero alcohol licence. In NZTA's data, about 68% moved to a zero alcohol licence within 18 months.
What happens after the interlock?
You move to a zero alcohol licence, which lasts 3 years and has a zero alcohol limit.
Can I get a limited licence if I have an interlock sentence?
No. A person subject to an alcohol interlock sentence cannot apply for a limited licence.