Until now, Adelaide was the only mainland Australian capital without a continuous, non-stop motorway — creating growing congestion and safety concerns as traffic and population increased. The missing link in the city’s north-south corridor, the River Torrens to Darlington (T2D) section, posed the greatest technical challenge: a 6.5-mile (10.5 km) stretch cutting deep through established residential areas.
To overcome this, the South Australian Government turned to an alliance, including Jacobs, to design and deliver the final piece of the 48.5-mile (78 km) corridor. Once complete, this infrastructure project will allow drivers to bypass 21 traffic lights and reduce travel times by up to 40 minutes.
Jacobs brings extensive experience in holistic infrastructure delivery, including global leadership in both tunneling and transportation solutions, to bring this transformational investment to life.
By easing congestion and improving traffic flow, the project is expected to unlock $153 million (AUD $230 million) in annual productivity gains for South Australia — making it a cornerstone of the region’s long-term economic growth.
As part of the T2D Alliance Jacobs is involved across all design disciplines, including roads and civil, stormwater, civil structures, geotechnical and buildings, as well as leading tunneling design, transport planning and construction integration for the corridor — and working to accelerate delivery. The project features two sets of three-lane twin tunnels — the southern tunnels and northern tunnels — linked by an open motorway.
(78 km) Length of Adelaide’s North-South Corridor motorway
(AU $15.4 billion) Total project cost
Estimated jobs supported annually during construction
Peak-hour travel time saved by bypassing 21 traffic lights
Final stretch of the corridor to be completed
Tunnel boring machines building twin tunnels simultaneously
Massive tunnel boring machines (TBMs) started arriving in October 2025, marking a major milestone in South Australia’s largest infrastructure project. Each machine measures about 328 feet (100 meters) long and 49 feet (15 meters) wide — making them the largest pieces of construction equipment ever used in the state. Two TBMs will launch from the southern precinct to create twin 2.8-mile (4.5-kilometer) tunnels, while a third will deliver the twin 1.4-mile (2.2-kilometer) northern tunnels. Procuring all three machines allows crews to work concurrently on both tunnel sections, ensuring efficient delivery of this landmark infrastructure project. The project also includes upgrades to local infrastructure, including walking and cycling paths, and revitalizing green space exemplifying our ability to deliver transformative outcomes while investing in community resilience and sustainability.
In June 2025, the T2D Alliance hosted an industry engagement event at the Adelaide Convention Centre, drawing over 700 attendees. The event showcased upcoming work packages and reinforced the commitment to supporting local businesses.
Jacobs is also supporting local workforce development and inclusion initiatives. With more than 300 South Australian businesses expressing interest, the project is creating a supplier legacy for the state.
At a ceremony in May 2026, the T2D project marked a critical milestone with the naming of the three TBMs and the blessing of the first, Mary. Following strong community engagement with more than 2,000 name submissions received, the TBMs were named Mary, Catherine and Elizabeth in honor of South Australian suffragists Mary Lee, Catherine Helen Spence and Elizabeth Webb Nicholls, whose advocacy helped make South Australia the first place in the world where women could both vote and stand for election.
Mary will soon begin tunneling from Clovelly Park toward Anzac Highway, with Catherine and Elizabeth expected to be operational by the end of the year. All three TBMs will then work to build the two sets of twin tunnels, bringing a non-stop South Road closer to reality.
Across aviation, rail, transit, highways, bridges and ports, Jacobs turns complex transportation challenges into systems that perform. Our global experience and local insight come together through integrated planning, design and delivery — supporting programs that keep communities connected and moving forward.
Delivering safe, resilient transportation infrastructure in complex ground and constrained environments
