It's thought 6,000 cases of drink driving will be prevented each year thanks to the new in-car breathalyser law.

Repeat and serious drink-drivers will now be forced to install breath-testing devices in their car.

The vehicle won't start if the offender has had a drink.

Sober Check managing director Gavin Foster told Mike Hosking the devices have made a huge difference in Australia and the US.

"Their reoffending rates when using interlocks dropped by up to 60 per cent which is pretty amazing compared to what we've got now."

LISTEN TO GAVIN FOSTER TALK WITH MIKE HOSKING ABOVE