All Victorian drink-drivers caught over the legal limit will be forced to install alcohol interlocks to their cars for at least six months, under tough new laws designed to drive down the road toll.

The Andrews Government will also consider lowering the legal blood-alcohol limit from .05 to .02 if evidence shows it will reduce the number of people killed on the state's roads.

Under the current system, most people caught with a blood-alcohol reading between .05 and .07 are fined and lose 10 demerit points.

But the legislation will mean anyone who is over the limit will also have to install an interlock for six months or more.

Roads Minister Luke Donnellan said the device would serve as a daily reminder to drink-drivers of their bad behaviour.

"Too many drivers pay the fine and forget about the potential consequences of drink-driving," he said.

"Fines and demerit points alone aren't working, more is needed to help reduce the number of Victorians who lose their lives or are seriously injured on our roads every year because of drink-driving."

Mr Donnellan said the Government would examine the evidence for reducing the drink-driving threshold.

"If the figures indicate that would improve behaviour we'd look at it, absolutely," he said.

"I'm sure some would think it's appropriate and some wouldn't think it's appropriate. We make no apologies for wanting to drive the death toll down."

Interlocks to cost offenders hundreds of dollars

Mr Donnellan said people caught between .05 and .07 would not automatically lose their licence at this stage, but a magistrate could still strip them of their licence in court.

Interlocks are installed at the drivers' expense and stop them starting the car without passing a breath test.

One in five drink drivers are repeat offenders, police statistics show. ( Supplied: Erin Stutchbury )

Drivers will be charged $170 to have the device installed, $150 per month to use them, and $100 to have them removed.

Assistant Police Commissioner Doug Fryer said the change would make Victoria's roads safer.

"If you have more than .05 in your system you double the chance of crashing on the road, at .07 it's four times, it just goes up and up," he said.

Mr Fryer said the blood-alcohol limit might need to be lowered for people aged between 21 and 25, because they were over-represented in drink-driving statistics.

Police statistics show about 13,000 drink-drivers are caught in roadside testing every year, with 2,500 in the .05 to .07 range.

About 20 per cent of drink-drivers are repeat offenders.

Mr Donnellan said the Government would introduce the legislation to Parliament soon.