The Timber Truss Bridge Strategy

Background

Transport for NSW manages most of the remaining timber truss road bridges (TTBs) in NSW. Through the regional rail network it also is responsible for the remaining timber truss bridges on former rail lines.

Over time most of the more than 450 TTBs have been replaced by more modern bridges, but it is recognised that the remainder have high individual and collective heritage significance, being nationally unique in their technological development and forming a record of NSW’s non-Aboriginal settlement history.

In 1999 the Roads and Traffic Authority commissioned an overview of the 82 road TTBs still standing. The report identified a number of bridges considered to be of the highest level of heritage significance, which were added to the NSW State Heritage Register.

Retaining bridges on their heritage merit alone caused problems with some bridges because they were unable to meet modern operational demands from increasingly heavy vehicular freight traffic. For other bridges, such as Dunmore, Morpeth and Junction Bridge near Tumut, it prompted long-overdue repairs and capacity upgrades that gave these new bridges life and continued service and made us appreciate again their beauty and intricacy.

Need for a strategy

The need to reconcile the conflicting demands of heritage conservation and providing safe operation was first addressed in the Timber Truss Road Bridges – A Strategic Approach to Conservation (the Strategy) in 2010. The Strategy identified 26 out of the 48 then extant TTBs that Roads and Maritime committed to retaining and conserving because of their heritage value and importance to the state. The bridges selected represented the range of former bridge types, their age, sizes and diverse configurations. They were also on roads which were forecast to not have a freight demand beyond what the bridges would be able to carry.

In 2011, with the support of the NSW Heritage Council, Roads and Maritime consulted the NSW community and stakeholders. The Strategy was amended in response and the final version of the Strategy was endorsed by the NSW Heritage Council in 2012.

The endorsement of the Strategy provided improved certainty for the Heritage Council about our commitment to their conservation, and also directed our bridge maintenance program how to best spend limited resources. The Strategy was considered a landmark in progressive heritage conservation approaches at the time.

Review of the strategy

About six years after the Strategy began, with the benefit of better understandings of the structural truss types and strengthening methods available which conserve heritage values while providing adequate capacity to keep bridges operational, it became clear that the Strategy needed to be amended.

A revised Strategy was developed. Of the 26 bridges to be retained under the 2012 TTB Strategy, seven were unable to be modified to meet community and network needs while retaining their heritage value and were identified to be removed from the list of those to be kept. To balance them, eight other bridges were reassessed and were found able to be kept, giving an updated number of 27 bridges to be retained.

This included some bridges that had been owned by local government which had previously not been included in the first strategy, but it had become clear that they were more vulnerable to limited funding and that including them in the Strategy went some way to ensuring the survival of several better examples.

Where we are today

The revised list of bridges to be kept under the Strategy was endorsed by the Heritage Council in June 2019. It continues to protect a representative sample of 27 TTBs within the operational road network, where they can receive maintenance funding and are managed consistently, with their high heritage values being conserved.

A similar approach to the development of a conservation strategy is planned for the rail timber truss bridges.

These are the 27 road bridges to be retained under the Strategy: