Drivers should be allowed to turn left on a red light at more intersections in South Australia in an effort to reduce road congestion, according to the State Opposition.

The practice is only allowed at six intersections state-wide but the Liberal Party said Australia Road Rules allowed it wherever a "left turn on red permitted after stopping" sign was located.

"I see this as another opportunity to do what is working in the eastern states," Opposition Transport spokesperson David Pisoni said.

"You can go to corners in Sydney where time and time again you can turn left on a red signal when it's signed to do so and it's safe to do so."

The Liberal Party will this week introduce an amendment to the Government's Road Traffic (Roadworks) Amendment Bill, which is aimed at preventing poor usage of roadwork speed limit signs.

It proposes only to legalise left-hand turns on a red light where the speed limit was 60 kilometres per hour or less.

Mr Pisoni wanted the SA Transport Department to conduct regular audits of traffic light-controlled intersections to identify where the practice could occur.

SA Government cites danger to cyclists and pedestrians

But State Transport Minister Stephen Mullighan said Mr Pisoni's push was "deeply concerning" because turning left at red lights could be "dangerous, especially for cyclists and pedestrians".

He said the Government had trialled left turns at 11 sites in the metropolitan area after the Australian Road Rules were changed in 1999.

Mr Mullighan said it was removed from five intersections because the trial found too many drivers did not stop before turning left, as required by law.

He said the left-turning drivers were more focussed on finding gaps in the traffic than making themselves aware of "vulnerable road users in the vicinity, such as pedestrians".

"Despite the evidence, the Liberals want to extend these dangerous red-light turns across the network," Mr Mullighan said.