The Morrison and Marshall Governments are delivering the biggest ever job-creating infrastructure project in South Australia's history - the long-awaited final section of the North-South Corridor.
The River Torrens to Darlington stretch will be transformed over the next decade with a combination of tunnelling and at-surface infrastructure to unlock Adelaide's traffic network and create up to 4,000 jobs.
The final 10.5km section is the most complex part of the North-South Corridor to deliver and has required extensive analysis of a number of design options including one long tunnel, an at-surface motorway and a hybrid combination of both.
Comprehensive analysis of traffic, ground conditions, local environment, heritage assets and also community and stakeholder feedback has confirmed the hybrid+ option will deliver the greatest social and economic benefits for South Australia.
The project will be delivered in two stages. Stage One - approximately 6km of motorway including more than 4km of tunnel between Anzac Highway and Darlington and Stage Two - an at-surface motorway and a second northern tunnel, connecting the River Torrens to Anzac Highway.
Prime Minister Scott Morrison said the North-South Corridor would deliver thousands of jobs to support hard-working South Australian families and motorists would benefit for generations to come.
"The North-South Corridor is a game-changing piece of infrastructure that will change the way people move across Adelaide," Mr Morrison said.
"This is the most significant and eagerly anticipated road infrastructure project ever delivered in South Australia."
Premier Steven Marshall has predicted the North-South Corridor will be one of the most important infrastructure projects ever delivered for our state and will revolutionise the way we travel.
"This project is a generational game changer for South Australian motorists - and the largest delivered in more than a century," said Premier Steven Marshall.
"The benefits of our decision will be felt for generations, with the project alone estimated to create up to 4,000 jobs, slash travel time by 24 minutes and connect the north and the south of our state with a 78km non-stop motorway."
Federal Minister for Population, Cities and Urban Infrastructure, Alan Tudge, said tunnelling will remove thousands of vehicles a day from South Road.
"This will slash up to 24 minutes in travel time from River Torrens to Darlington, that equates to more than eight days across a year that motorists will save," Mr Tudge said.
"When the entire corridor is complete it will deliver a 78km non-stop, free-flowing motorway from Gawler to Old Noarlunga."
South Australian Infrastructure and Transport Minister, Corey Wingard, said progressing the hybrid+ solution means we can maximise the project's benefits, including a free-flowing north-south motorway.
"After the previous Labor government put this project and tunnels in the too-hard basket, we've rolled up our sleeves and done the work to get it back on track," Minister Wingard said.
"The tunnelling solution we've come up with will minimise community impact, improve east-west travel, increase overall network capacity to reduce congestion, and deliver greater safety benefits.
"The other design options we assessed failed to meet the state's transport needs while getting the balance right between easing congestion across the network and enhancing the liveability of local communities - key objectives for the project.
"With the hybrid+ solution we can protect iconic community and heritage assets including the Thebarton Theatre, Hindmarsh Cemetery, Hoffman Brick Kiln and Queen of Angels Church, to name a few.
"This solution requires far less property acquisition, will have reduced impact to business during construction and saves a number of heritage buildings from demolition."
The motorway will be built in two stages, with Stage One focused on improving the most congested area of the network and delivering free-flowing travel between Anzac Highway and Darlington.
Most of this first stage will involve tunnel construction, meaning work can occur while minimising disruption to South Road traffic, businesses and the local community.
This stage will be built within the existing joint state and federal funding commitment of $5.4 billion, delivering a faster return on investment and early benefits to road users.
Current estimates put the total 10.5km project at $8.9 billion. The final cost estimate will be determined later next year after a detailed business case and consideration by Infrastructure SA and Infrastructure Australia.
The current estimate is around $1 billion less than the initial estimate for this tunnelling option following further project design and refinement, which has also resulted in 480 fewer property acquisitions than Labor's open motorway option.
The project will now progress to the next stage of development including ongoing ground investigations, detailed design work and a comprehensive stakeholder engagement program to inform a reference design which is expected to be released late-2021.
Early works including ground investigations are already underway, with utility relocation works scheduled to start in 2021 and major construction expected to commence in late 2023. Construction is to be completed by 2030.
