A key element of the $885 million Northern Connector project will open in Adelaide on Tuesday.
The six-lane, 5.5 km motorway links multiple popular highways and expressways across the state.
The new overpass will open to traffic about 6am from Waterloo Corner, in Adelaide's north.
Urban Infrastructure Minister Alan Tudge said the project provides a vital freight and commuter link between the Northern Expressway, South Road Superway, Port River Expressway and the Salisbury Highway.
"It forms part of the coalition government's $5.3 billion investment in public transport and road infrastructure across South Australia," he said in a statement.
About 14,000 tonnes of asphalt and 650,000 tonnes of fill were required to build the interchange.
The federal government has committed $708 million to the project, while $177 million is being put in by the South Australian government.
SA Transport Minister Stephen Knoll said the government continues to grow its investment in infrastructure.
"As the Northern Connector project reaches its job's peak, it's important the government continue to add to the record infrastructure pipeline of works in South Australia," he said.
"The government has been working hard and working collaboratively with the federal government to secure new funding for projects to provide a continuous pipeline of construction work and jobs."
The project is scheduled for completion in late-2019.
