More than a kilometre of temporary throw screens has been installed on bridges along Adelaide's Southern Expressway in an effort to prevent rocks being hurled at vehicles below.
SA Police said there had been 44 rock-throwing incidents along the expressway between Adelaide and Noarlunga since January.
The majority of those have involved objects being thrown from an overpass or bridge, but projectiles have also come from areas along the shoulder of the 18.5-kilometre expressway.
The road was duplicated between 2010 and 2014 by the former Labor government but throw fences were not installed despite bridges being extended.
SA Infrastructure Minister Stephan Knoll said it had been six weeks since the last confirmed incident and believed police responses to the situation along with "infrastructure solutions" had been successful.
"That's testament to the hard work of the police in the area who have really stepped up resources in trying to tackle this problem," he said.
"[They have] done a fantastic job in reaching out and integrating with the community to make sure we can have these incidents stopped.
"But it's also testament to the infrastructure solutions that we've been putting in place."
All road and pedestrian bridges across the expressway are now fitted with temporary or permanent throw fences, while fence netting has been laid over loose rocks along some expressway embankments.
CCTV camera coverage has also increased.
Fences 'not tall enough'
But those commenting on the design through Facebook said the fences were too low and rocks could simply be thrown "over the top".
A user named Wayne Sampson said he suspected somebody was "making money out of it all, probably laughing all the way to the bank".
Another user named Gordon Crabb suggested the fences needed to curve inwards at the top and were not tall enough, while Robby Cummins claimed engineering and fabrication firms in SA could have a different design installed in less than a month.
Mr Knoll said permanent anti-throw screens were still being designed ahead of their installation later this year and they would replace the temporary fences.
