Main South Road duplication milestone: design and safety notes for road engineers
Reviewed by Tom Sullivan
First reported on Roads & Infrastructure (AU)
30 Second Briefing
The second stage of the Main South Road Duplication Project has opened to traffic in Adelaide, doubling carriageway capacity between Aldinga and Sellicks Beach and removing a key bottleneck on the Fleurieu Peninsula corridor. Delivered by the Fleurieu Connections Alliance, led by CPB Contractors, the works convert this section of Main South Road from a single to dual carriageway, with new intersections and median separation improving traffic flow and crash risk performance. For civil and pavement engineers, the duplication sets the geometric and structural standard for future upgrades further south.
Technical Brief
- Median separation and access control were designed to reduce high‑severity head‑on and right‑angle crash types.
- Construction staging maintained traffic under live conditions, requiring temporary barriers, reduced speeds and night works.
- Road geometry, sight distances and crossfall were upgraded to contemporary design standards to reduce run‑off‑road incidents.
- Drainage and verge treatments were re‑worked to minimise hydroplaning risk and improve clear zones for errant vehicles.
- Lessons on alliance contracting and staged duplication under traffic are directly transferable to other regional corridors.
Our Take
CPB Contractors features across multiple Australian Infrastructure items in our database, and its repeated selection on South Australian road schemes suggests state agencies are favouring large Tier 1 contractors for complex duplication and safety upgrades.
Among the 707 Infrastructure stories, relatively few focus on peri-urban corridors around Adelaide, so the Main South Road Duplication Project stands out as one of the more substantial recent investments in South Australia's coastal commuter and freight links.
With this project tagged under both ‘Projects’ and ‘Safety’, it aligns with a cluster of recent Australian road pieces where safety outcomes (separation of traffic, intersection treatments, and speed environment changes) are treated as primary performance metrics rather than secondary benefits to capacity increases.
Prepared by collating external sources, AI-assisted tools, and Geomechanics.io’s proprietary mining database, then reviewed for technical accuracy & edited by our geotechnical team.
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