Compulsory installation of alcohol interlock devices for repeat drink-driving offenders was the most effective way of changing their behaviour, according to a Northland company contracted to install the equipment.

Gavin Foster, owner of Smart Start Interlocks, made the comments while welcoming an announcement by the Government last week that alcohol interlock sentences would soon become mandatory for serious and repeat drink-drivers.

Judges currently have discretion whether to impose the sentence. But a change in legislation will mean anyone convicted of two or more drink-driving offences within five years and any first time offenders caught driving with more than 3.2 times the legal alcohol limit of 250 micrograms per litre of breath will be subject to an alcohol interlock sentence.

An alcohol interlock is a breathalyser wired into a vehicle's starting system. To start the vehicle, the driver must pass a breath test.


Mr Foster said the new changes were on par with research around the world that compulsory installation of the devices reduced repeat drink-driving offences.

"Most people regard it as an easy option but it's not. People who've had a vehicle comply with the sentence will tell you how it's changed their behaviour.

"Sentences such as disqualification and fines haven't changed the behaviour of repeat drink-drivers. Their repeat offending, which is second or more conviction within five years, has gone up," he said.

The alcohol interlock sentences came into effect in September 2012 and Mr Foster's company started installing the devices in January 2013.

He said only seven or eight installations took place then.

Cost was signalled as a major reason why judges in Northland were reluctant to impose alcohol interlock sentences.

Mr Foster said it cost $2500 annually - or $6.80 per day - but once it was made compulsory, offenders who could not afford to pay could tap into partial government funding. Government has set aside $4 million to help pay for compulsory installation.

Associate Transport Minister Craig Foss said New Zealand's road toll was too high and drink-driving caused an average of 77 deaths, 436 serious injuries and 1252 minor injuries every year.

"Mandatory interlock sentences are a targeted and effective way to help spare families, friends and communities the pain and suffering that inevitably follows each and every one of those crashes.

"Research shows interlocks reduce reoffending rates by about 60 per cent," he said.