O-Bahn City Access Project


Customer: Department of Planning, Transport and Infrastructure 

Contract: Design & Construct

Location: Adelaide, South Australia




Transport Solutions Australia

Fast Facts

  • 670 m tunnel construction
  • 2,000 tonnes of steel
  • 450 jobs created for the project
  • Over 70,000 m³ material excavated
  • 2018 CCF Earth Award for Excellence

The O-Bahn City Access Project builds on the SA Government’s investment in a stronger public transport network. Its primary objective was to improve travel times and reliability for users of the O-Bahn service and to reduce traffic congestion and delays, particularly on the Inner Ring Route.

Specifically, the project extended the O-Bahn system from the end of the busway at Gilberton into the cross-city priority bus lanes on Grenfell Street, and included the creation of centrally aligned priority bus lanes along Hackney Road and a dedicated 670 metre bus tunnel providing quicker, more reliable access for O-Bahn buses into the city.

Rundle Road and East Terrace were also reconfigured to deliver pedestrian, cycling and vehicle improvements. A shared pedestrian/cycling path was provided on the western side of Hackney Road between Bundeys Road and Botanic Road including a new shared use pedestrian/cycling bridge over the River Torrens.

The Project was situated within a complicated and sensitive environment; delivery occurred within a two-kilometre corridor in a highly trafficked, brownfield environment in the heart of Adelaide’s CBD, with complex traffic and logistic requirements, and adjacent operating stakeholder businesses and residences with varying priorities and needs.

The multi-disciplined scope included tunnel construction of various types (sheet-pile tunnel in road reserves and cut and cover insitu/precast concrete box tunnel in the Park Lands); new bridge construction and existing bridge widening and strengthening; existing road widening and new road construction including all utility and public service relocations.

The O-Bahn tunnel is the only guided bus-only tunnel project in Australia. The design is based on current best practice in road tunnel design standards, however the unique nature of a guided bus-only tunnel allowed the team to develop and optimise the design.

The result was an innovative design with different tunnel construction methodologies used along the length to suit the construction constraints. Tunnel services use the latest technology and system integration principles to deliver a safe, operational tunnel with reduced whole of life costs.

Key to the Project’s success was the collaborative team environment developed over the project life amongst a large number of project partners and consultants. This ‘One Team’ and best-for-project culture meant that all participants took a genuine approach to delivering an outstanding piece of infrastructure.

The O-Bahn City Access Project demonstrates engineering excellence across all facets, as well as a highly integrated, collaborative engineering and construction approach and innovation in delivering multi-disciplined infrastructure outcomes for the community and daily O-Bahn users.


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