Strengthening a major corridor of Adelaide

Adelaide’s north-south road corridor is a vital route for the region’s motorists and freight heading to key transit hubs. Rising congestion problems, low travel speeds and low productivity were triggers to the redevelopment of this route.

The Torrens Road to Torrens River Project, also known as T2T, forms a crucial part of the north-south corridor. This section marks one of the busiest sections of what is a major Adelaide north-south corridor for traffic. It will be a 4 km non-stop section of road, providing significant travel time savings for commuters and freight.

Turning the key on travel times

In 2015, Aurecon, in alliance with CPB Contractors and South Australian company York Civil, appointed by the Australian and South Australian governments to design and construct the T2T project. The upgrade to this section of the corridor will provide motorists with a non-stop route for 4 km from the River Torrens to a point north of Torrens Road, significantly improving travel times. As part of the T2T Alliance, working with sub-alliance design partners W&G and Mott MacDonald, Aurecon is providing design management, detailed design and construction oversight services.

Upon completion in 2018 it is envisioned to vastly improve freight and commuter traffic congestion and travel times.

The project includes:

• A 3 kilometre section of lowered non-stop motorway
• Parallel surface (at-grade) roads along the length of the lowered motorway to connect local roads and arterial roads to South Road
• An overpass of the Outer Harbor rail line
• Three major road bridges, a pedestrian bridge and a services bridge over the lowered motorway
• Various intersection upgrades
• Improved cycling and pedestrian facilities
• Improved cycling and pedestrian facilities
• Landscaping and noise barriers
• Major services relocation and accommodation works, including HV power, sewer, telecommunications and gas

3D modelling at your service

The construction of the 3 km lowered motorway in this section required the movement and accommodation of a very large number of pre-existing utility services. South Road is not just a busy traffic conduit, but also a critical corridor for major services for Adelaide. A large and sensitive high voltage sub-station, positioned near the centre of the project, had to be accommodated. All the affected electrical cables feeding into this substation were moved underground as part of T2T. 

“The complete disruption of the utility services along South Road would be a disaster for Adelaide, which is why we needed solutions to ensure uptime during this part of the project,” says Turner.

In order to minimise risk of service strike and create a useful legacy model for the client, Aurecon constructed a 3D model that showed the location of the thousands of services along the route.

"The 3D model that we built enabled us to look at how we can provide an asset to the South Australian Department of Planning, Transport and Infrastructure. We’ve mapped all of the services to get a tool that shows the legacy of the infrastructure that exists underground through this area,” says Paul Steendyk, T2T Alliance General Manager.

Giving community a voice

A great deal of consideration also went into the noise impact on residences and businesses in close proximity to South Road. Walls between 2.4 and 3.5 m high were erected to reduce the sound pollution from operational road noise. Residents were consulted individually to agree on appropriate acoustic modifications that could be made to each house.

“A significant amount of consultation and liaison with residents, designers and urban planners was needed to get the right balance of solutions for acoustic comfort,” says Turner.

The flow towards digital

“Traffic flow is arguably more important on this project than any other that I’ve worked on because South road in Adelaide is unique,” says Turner. "There is no other road like this."

"The fact that this key road is subject to heavy freight and commuter traffic all day meant that Aurecon and its partners couldn’t adopt a normal road upgrade approach by narrowing the lanes or reducing the speed because the impacts on the wider Adelaide network would be huge.”

Maintaining the traffic flow on the road was a key outcome that the project team had to achieve, and this has been done in three key ways:

1. Analysing traffic

   Under the terms of the T2T Alliance contract, the Department of Planning Transport and Infrastructure (DPTI) would specifically penalise the team for affecting traffic flow between 7am and 7pm on weekdays. Given the unusual nature of South Road, “peak” conditions do not apply to the same degree as most roads, so this 12 hour window was mandated, within which traffic performance was measured. 
   
   
   
   Major disruptions were scheduled outside of these times, but not all work could be arranged for evenings or weekends. In order to determine the effect of the many temporary road configurations, microsimulation modelling of the various scenarios was undertaken. The results were calibrated against measured traffic performance, generally indicating good correlation.

2. Working safely next to the road

   The conventional approach to the construction of a project such as T2T would be to use temporary traffic cones and involve many controllers that regularly engage with traffic. Based on the agreed temporary traffic arrangements that are described above, the project team set up infrastructure, which included rigid barriers that allowed them to safely work next to the traffic. Digital Variable Message Signs and excellent web based communication tools kept the public informed of the various changes in configuration.

3. Signalling progress with Bluetooth

   Real-time traffic flows are measured and compared to the times that were recorded from prior to the commencement of construction. DPTI installed Bluetooth devices throughout the Adelaide traffic network as part of its award-winning Addinsight Traffic Intelligence System. This provided network-wide performance indicators in real time, allowing the public to readily track travel times and incidents throughout the network using their smart phones and the Addinsight app.
   
   
   
   The signalling stations that have been installed can track the travel times from point A to B with a high degree of accuracy. The data was collected with the assumption that 15 to 20 per cent of all vehicles carry an active Bluetooth device. This traffic information was broadcast on a large screen in the project office and it was used as a method to determine exactly how the upgrade was affecting traffic flow. At the beginning of 2017 the results showed that traffic on some sections of South Road had actually improved from before the project had started.
   
   “It’s very easy to become consumed with the day-to-day challenges of delivering design packages on time and overcoming technical challenges on projects of this magnitude. But the project team continued to maintain focus on the big picture, which is making life better for people and delivering value to the community,” says Turner.
   
   

"The fact that the traffic flow was better during the construction of a major road upgrade compared with normal conditions is a testament to our project team, but also to what the client and the Commissioner of Highways wants to achieve from this project," concludes Turner. "The controlled temporary roundabout at Grange Road, which was put in place to allow a bridge to be constructed inside the circle, actually performed better than the old signalised intersection."