Work has begun on upgrades to about 115 kilometres of the Ngarkat Highway, between Pinnaroo and Bordertown.
Various work - worth $16.37 million in total - will be undertaken until the second quarter of 2021, weather permitting.
This includes sealing shoulders, resurfacing about 11km of the road, improving road delineation, replacing guide posts, updating line marking, installing audio tactile edge lines, and putting up about 2km of safety barriers.
A Department of Planning, Transport and Infrastructure spokesperson said the shoulder sealing would reduce the risk of run-off road crashes, while the audio tactile edge lines will alert drivers when a vehicle goes off the road, providing extra safety for motorists.
Workers will be onsite between 7.30am and 5pm from Monday to Saturday, and while the highway will remain open while they work, a 40km/h speed limit is in place.
There may be other lane and speed restrictions, depending on onsite conditions.
Access to properties along the highway will be maintained.
The upgrade is part of the State Government's plan to raise the speed limit to 110km/h on the highway.
All works are part of the Federal and South Australian Governments' $143 million 'Rural Roads Package - Safety Package' which will deliver significant safety upgrades across the state.
In total, $70 million from the $143 million package will target safety improvements on more than 423 kilometres of country roads.
All works, including the final speed limit increase, are expected to be finished by April next year.
Anyone with questions about the project can email firstname.lastname@example.org or call 1300 794 880.