Bridges

This paper proposes the establishment of a funding program for the systematic replacement of end-of-life timber bridges owned by the Queensland Department of Transport and Main Roads (TMR). The initiative aims to address TMR’s priorities on a consistent statewide basis through a sustainable approach to managing timber bridges, encompassing maintenance, rehabilitation, and replacement. This project seeks to balance context, demand, cost, risk, and performance, with a focus on whole-of-life costs.

The core issue is clear: the nominal expected life of a timber bridge is 80 years, yet the average age of TMR’s timber bridges is 75 years. TMR has over 280 timber bridges, representing less than 10% of its bridge inventory but incurring significant maintenance costs. In some districts, annual maintenance expenditure on timber bridges exceeds 50% of the available budget for bridge and culvert maintenance. Statewide, timber bridge rehabilitation costs consume 15-20% of the available rehabilitation funding for only 4% of the network. This disproportionate expenditure is unsustainable, inefficient, and compromises the maintenance of non-timber bridge assets. The current condition of timber bridges exacerbates the challenge, with 65% rated as poor or very poor and approximately 50% structurally inadequate for TMR’s standard heavy vehicle tasks. Additional concerns include road safety issues related to bridge barriers and narrow access.

Addressing this challenge needs to be consistent with TMR’s visionary principles of a transport system that is responsive and resilient to the changing environment. Therefore, a focused investment and innovative delivery solutions are essential. The proposed Timber Bridge Priority Replacement Program aims to develop a systematic process for prioritising and funding the replacement of uneconomical timber bridges. Strategic planning has been completed with the development of a prioritization tool that incorporates targeted criteria focused on road usage, specifically low-volume traffic roads, and the optimal cost of bridge replacement. The concept phase of pilot delivery works is currently underway, serving as an output for an investment strategy and the adoption of innovative design and construction solutions. This approach aims to enhance the sustainability, safety, and efficiency of the transport network