What we delivered

  • Developing an innovative design solution to transform the Caloundra Road interchange into a Diverging Diamond Interchange (DDI) to tackle traffic. 

  • Rectifying the conflicts of conventional intersections that cause congestion, delays and crashes by conveying traffic in different forms.

  • This project helped develop new Australian road design guidelines to inform future implementations of the DDI in Queensland and shared more broadly across Australia

Get in touch with our team

Arup, in a joint venture with Jacobs, was engaged as the designer for the Fulton Hogan Seymour Whyte Joint Venture (FHSW JV) to construct the Bruce Highway Upgrade, from Caloundra Road to Sunshine Motorway (CR2SM) on behalf of Department of Transport and Main Roads (TMR). The project team developed an innovative design solution to transform the Caloundra Road interchange into a Diverging Diamond Interchange (DDI) - the first of its kind in Australia.

Like roundabouts, DDI’s tackle the interchange conflict points that cause congestion, delays and crashes by removing traffic, or conveying the traffic differently altogether and resulting in profound traffic performance and safety improvements. Compared to equivalent conventional upgrades, these treatments can provide up to 50% more traffic efficiency and over time are significantly safer due to removing the intersections’ severe crossing points. 

CR2SM is a great example of innovating for impact, using fresh thinking to consider the environmental, social and economic implications and demonstrating how we can do things differently. 

Planting the seeds of design innovations

The DDI concept was first presented by Arup 10 years ago for a different high-profile Southeast Queensland TMR project, and although the concept wasn’t the right fit, it planted the seed for innovation, ultimately showing TMR we wanted to push the boundaries of Australian road design. So, when the Bruce Highway Upgrade CR2SM project arose, we knew it was the perfect opportunity to put this innovation back on the table. 

Innovating for impact video
The CR2SM project is a great example of innovating for impact, using fresh thinking to consider the environmental, social, and economic implications and how we can do things differently.

Bringing DDI to Australia

Through Arup’s global skills network, our San Francisco team introduced our Queensland team to Gilbert Chlewicki, based in Washington DC, who is recognised for creating DDI’s concept and the driving force behind his ground-breaking design across the US. Arup invited Gilbert for a speaking tour across Australia, discussing the concept and success stories from the 60 plus interchanges already built in the US with state government highway organisations. 

During this Australian tour, we paid particular attention to Queensland and TMR. We explained that while innovation may seem risky, this approach introduced new ideas in a tempered way using previous examples and experience from the US. Not long after this engagement, we were appointed to the project and visited the US to see the new concept in action and develop a detailed understanding of DDI design, construction and operational aspects. 

The completed interchange
The completed Diamond Diverging Interchange at Caloundra © Department of Transport and Main Roads

Employing sustainable road design techniques

The CR2SM Bruce Highway Upgrade opened in 2020, with the design’s positive impact already being noticed by many. Choosing this design led to the reuse of 130,000m³ of material and a 29-hectare footprint reduction on the Mooloolah River National Park, conserving this environmental and culturally significant space for the future. The design has proved safer, by reducing traffic incidents and travel time through the interchange. In addition, the new highway provides active transport infrastructure for cyclists, pedestrians, new carpool and bus stop facilities. 

Infuencing the way clients approach their projects

TMR has now adopted the DDI methodology for more interchange sites across Southeast Queensland. This project helped develop new Australian road design guidelines to inform future implementations of the DDI in Queensland and shared more broadly across Australia.