P-plate drivers in their first year will be subject to a night curfew and banned from carrying more than one young passenger in a bid to lower the road toll.

The changes will be introduced to South Australian Parliament later this year and also include extending the minimum provisional licence period from two to three years.

First year drivers will be restricted from driving between midnight and 5am and only allowed one passenger between the ages of 16 and 20.

Drivers will not be able to graduate to a full licence until they are at least 20 years old.

The legislation will also see an end to regulations that require young drivers to regress to an earlier licence stage after a period of disqualification.

The State Government says the high rate of road deaths among young drivers has prompted the proposals.

Road Safety Minister Michael O'Brien says South Australia has the country's second-worst road fatality rate for 16 to 19 year-olds.

He says similar restrictions have succeeded in reducing road deaths in Victoria and New South Wales.

"We know that people progressing from Ls to Ps within a matter of weeks have a tendency, a statistical average of six times the number of accidents that they had when they were on their Ls," he said.

"The first year people are on their Ps, they are the most accident prone.

"Around 3 per cent of young drivers in that P1 period have an accident compared to five years down the track where they only have 1 per cent, so after five years their rate of accidents is actually reduced by two-thirds

"It's really to deal with a lack of maturity and lack of experience but particularly maturity and that's why in large part we've imposed the ban on carrying more than one passenger and the night-time curfew.

"A ban on carrying more than one passenger aged 16 to 20 is going to significantly reduce the numbers of deaths and serious injuries amongst our P-platers."

Mr O'Brien says exemptions to the curfew and passenger restriction will apply, including cases in which young people need to drive to work.

He says the Government opted against a proposal to raise the minimum driving age from 16 to 18 because of community opposition but has urged parents to consider it for the future.

'Draconian'

The RAA says it supports the proposed changes which will save lives.

RAA spokesman Charles Mountain says the changes are similar to those the association recommended to the graduated licensing scheme.

"I think the proposal to have a night-time curfew for drivers in their first 12 months of Ps is a very good strategy and that's proven to be effective interstate and also brings us into line with the existing system they have as well," he said.

The State Opposition has labelled the changes draconian but transport spokeswoman Vickie Chapman says the Liberals are still weighing up whether to support the plan.

"We are prepared to look at legislation but on the face of it this is an unreasonable imposition on young people and their families without any demonstrable benefit," she said.

"We will work with the Government on any initiative that will help young people's lives be saved on the roads but we have a number of concerns.

"The concerns include the accessibility for young people to public transport and taxis in outer metropolitan areas and the country."

Ms Chapman says exempting family members from the limitation on the number of young passengers makes no sense.

"The absurdity of that on the face of it is that you can put your sister at risk but not your girlfriend," she said.

Ms Chapman says the Opposition has been denied access to more than 1000 community submissions on the proposals.

"We need to sit down, look at the legislation, require the Government to show us the data that supports what appears to be a draconian impediment for young people," she said.