RAA is renewing its call for the next Federal Government to commit $2 billion to duplicating Dukes Highway as crashes on the road continue to add to the state's spiralling road toll.
Senior Manager Road Safety Charles Mountain said the busy single-lane highway was notorious for crashes, especially head-on collisions.
"There have been three fatal crashes on Dukes Highway in the past six months and these tragedies underscore the need for government to take urgent action," Mr Mountain said.
Before these latest deadly crashes, the highway's grim road toll already stood at 12 deaths and 96 serious injuries between 2013 and 2017.
Dukes Highway is South Australia's busiest regional freight corridor with thousands of passenger vehicles travelling alongside more than 1100 commercial vehicles on single carriageways each day.
"Mixing passenger and freight traffic, such as B-doubles, on single lanes is a recipe for disaster," he said.
"RAA is calling for all political parties to commit to the staged duplication of Dukes Highway between Tailem Bend and the border with Victoria to prevent more tragedies and senseless loss of life."
In addition to the lives saved and injuries avoided by upgrading the highway, RAA points to the strategic importance of Dukes Highway as a major route between Adelaide and Melbourne.
"Dukes Highway is a vital arterial link to domestic and export markets for agriculture, forestry and fishing industries in the Coroong, Tatiara and Limestone Coast regions," Mr Mountain said.
"The Victorian government has already committed to duplicating Western Highway which connects to Dukes Highway.
"Ultimately we want to see two lanes in both directions for the entire length of Dukes Highway, providing a non-stop two-lane connection for the capital cities of Adelaide and Melbourne," Mr Mountain said.
"This will position the highway and South Australia at the forefront of Australia's autonomous freight innovation and operations."