Medlow Bath Pedestrian Bridge creates a new vantage point while improving accessibility

The Great Western Highway (GWH) is one of Australia’s most historic roads and a key east-west connection out of Sydney. Over the last 100 years the NSW Government has progressively upgraded sections of the highway to make it safer and more reliable. 

From 2019 – 2023 Transport for NSW conducted planning, design and environmental approval of a series of proposed highway upgrades between Katoomba and Lithgow. 

As part of this investigation Transport investigated a wide range of upgrade options and the option selected for Medlow Bath was a surface upgrade of the highway, including duplication of the existing road, improved intersections and facilities, a new pedestrian bridge delivering improved access across the highway and linking to new lift access to Medlow Bath Station, and an upgraded active transport link. 

The footbridge is situated at Medlow Bath adjacent to the train station and is subject to strict heritage interpretation requirements. The new pedestrian bridge required approval from both the Heritage Council and a dedicated local community group. 

The access bridge had to comply with DDA requirements, minimise disruption of the highway, and appear visually recessive and seamless with minimal support locations.

GHD provided the engineering design services for the bridge and adjacent train station upgrades including:

• Structural and bridge engineering
• Geotechnical interpretation and pile design
• Civil, surface and hydraulic modelling
• Lighting, security, communications and electrical designs
• Safety assurance
• Bushfire and fire engineering assessments
• Lift shaft ventilation

Heritage and community engagement:
The local community and Heritage Council were directly involved in the development of concept options and selection of the preferred design. Three alternative layouts were originally presented for consideration, with the chosen layout then undergoing extensive iterative design and adjustment. This optioneering stage required rapid and intense structural engineering input to confirm the suitability and maintain a grounded design that aligned with community expectations and desires. 

Facing significant site constraints, the team developed complex solutions, incorporating novel engineering elements and construction techniques. These included the adoption of a closed-cell fabricated steel box girder to minimise weight and accommodate significant torsional moments, an end-bearing temporary splice design for rapid erection and seamless site splicing, supports integrated into the lift core to minimise visual clutter, a wrap-around tight radius viewing platform with integrated stairs, and a composite flooring system to provide a slip-resistant walking surface on icy mornings

Design Considerations:
The aim of the project was to create a seamless, visually recessive structure that responds to the environmental beauty of the location rather than detracts from it.

Extensive collaboration between the engineering, architectural and construction teams was instrumental in the development of design and ultimate successful outcome of the project.

A closed-cell steel box girder design was selected to minimise the structural depth and support locations, which combined with the flowing configuration reduces the visual impact. The bridge spans clear over the highway and cantilevers out to the vista of Megalong Valley on the west. The abutment and main pier lands adjacent to a 5 m embankment located between the highway and the main Western passenger/freight rail line connecting Sydney to Western NSW. 

Constructability:
Constructability was a key consideration during the development of the design. Fabrication, transport, handling, erection and disruption requirements all fed into the ultimate design of the box girder. A complex construction sequence and temporary splice design was devised through collaboration with the construction team and fabricator to minimise disruption to the local community and users of the Greater Western Highway.

The design achieved the desired compliant connection while minimising visual intrusion on the station and Hydro Majestic hotel through adoption of a complex alignment, innovative structural form, and minimised support locations and lifts. The Great Western Highway remained open throughout construction, except for a single, 48-minute closure to erect the main span.

The bridge created a new vantage point overlooking the Megalong Valley and has been described by the President of the Medlow Bath Residents’ Association as “the best bridge in the Blue Mountains”.