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Review brings a safer and better connected design for T2D motorway

Wednesday, 14 December 2022

A new design that improves connectivity and safety, and safeguards the fabric of local communities, has been unveiled for the crucial final section of the North-South Corridor (NSC).

Following a comprehensive State Government design and financial review, the 10.5km River Torrens to Darlington (T2D) section of the NSC will now incorporate major design changes such as the removal of large elevated roadways and the addition of new entry and exit ramps.

The T2D – consisting of two sets of twin tunnels, lowered and ground-level motorways, as well as overpasses and underpasses at key intersections – is estimated to cost $15.4 billion and be completed by 2031.

Once finished, it will complete 78 kilometres of non-stop motorway between Gawler and Old Noarlunga, and allow motorists to avoid 21 existing sets of traffic lights between the River Torrens and Darlington.

Key proposed changes to the project announced by the State Government include:

  • Torrensville area – At the northern portal of the Northern Tunnels, near where the T2D Project connects to the North-South Motorway, a proposed large elevated roadway running parallel to the Brickworks Marketplace has been removed, with the motorway corridor moving to the east. Instead, a shorter, low-height structure over the corner of the Hindmarsh Cemetery will be constructed. This improvement, along with changes to the construction methodology, means the project will require less of Kings Reserve during construction than previously planned.
  • James Congdon Drive/Deacon Avenue – An additional exit ramp for vehicles travelling north has been added near this intersection, providing access to Richmond Road and James Congdon Drive. This means vehicles travelling from the south, heading north to go to Adelaide Airport or the western suburbs, do not need to go through the Anzac Highway intersection, greatly reducing the number of vehicles on the surface road there and increasing travel options for motorists. An additional entry ramp at James Congdon Drive has also been provided for traffic wanting to enter the motorway and head south.
  • Anzac Highway connection – The elevated ramp going over the motorway and South Road, before coming down onto the middle of Anzac Highway at Ashford to join with citybound traffic, has been scrapped. Instead, three ground-level right-turn lanes onto Anzac Highway heading towards the city will be provided, with an additional exit ramp from the River Torrens to Darlington motorway for northbound traffic, north of the Anzac Highway intersection. Right turns from Anzac Highway onto South Road – which were removed in the 2021 Reference Design – have been reinstated, acknowledging strong community feedback. This solution reduces traffic at the Anzac Highway intersection and the number of trees needing to be removed (approximately 35 instead of 116).
  • Darlington connection – The southern portal of the Southern Tunnels will shift about 300 metres to the north to give traffic more distance and time to safely change lanes, while moving into and out of the new motorway. This provides the opportunity for better cross-corridor movement via a shared-use bridge, significantly reduces the duration of required closures of the Darlington motorway during construction (easing disruption for motorists), and reduces the length of the Southern Tunnels and the associated construction costs.

The project review has also recommended a revised delivery program, which will see construction of the Southern and Northern Tunnels undertaken sequentially, rather than with an overlap, in a more realistic approach to project timing and market capacity.

Early works are underway, with main construction works proposed to start in 2025, with tunnel-boring machine (TBM) works for the Southern Tunnels planned to begin in 2026 and project completion expected in 2031.

While some properties formerly earmarked for acquisition will no longer be required to deliver the new project, the design upgrade will result in a net increase of 112 properties required to construct the motorway.

In early 2023, the T2D Project will undertake a series of community information sessions along the alignment to engage with interested stakeholders and gain local insights to further inform the Project’s design.

Details on these sessions will be communicated early in the new year. A new project community hub at 1194 South Road and drop-in centre at the Brickworks Marketplace are now open for visitors. People are also able to book individual meetings with project staff at key locations across the corridor by visiting the project’s website or calling 1300 951 145.