The 3000t, 180m-long bridge was constructed offsite and moved into place using self-propelled modular transporters, similar to remote-controlled trailers.
A second bridge is scheduled to be installed later this year via the same method and will deliver northbound Main South Road traffic over the Southern Expressway to the non-stop lowered motorway.
The Darlington upgrade is part of a $5 billion infrastructure spend in South Australia.
“The Turnbull government is backing these key infrastructure projects in South Australia to ease congestion, and this is possible because of a stronger economy,” Federal Urban Infrastructure minister Paul Fletcher said.
“The Turnbull government will continue to work with the Marshall government to deliver key infrastructure projects for South Australia, including the completion of the remaining sections of the North-South Corridor.”
The project is now 65% complete and has so far supported approximately 370 jobs per year during construction.
The project is expected to be completed by mid-2019 and is jointly funded – with the Australian government contributing $496 million and the state government contributing the remaining $124 million.