Tunnel – Risk Assessment & Mitigation Strategies (r2a Case Study)


This report covers fire and other tunnel hazards, and describes best practices for tunnel risk mitigation.

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In Australia, there appears to be no single agreed approach to tunnel design and fire protection. Even within the states there are different criteria and approaches. Compared with Europe, Australia has limited experience with long tunnels. Even so, Australian tunnels are unique. They provide deluge systems, which is not the norm overseas. They are also regularly subject to small fires, but there have been no recorded large fires to date. The performance of Australian tunnels for large fires appears to be empirically untested, which is also unique.

The conventional approach to tunnel risk management in Australia is exemplified by the “Emergency Response and Incident Management Plan” developed by the Roads and Traffic Authority of New South Wales. Risk assessment and mitigation strategies are nowadays developed through the Environmental Impact Statement (EIS) process and embodied in prescribed standards and services. For example, a 50 MW maximum single incident hydrocarbon fire is to be fully controlled by mechanical ventilation and smoke control systems.

The authors note that until recently, Australian road safety authorities have not adopted a risk-based approach. In addition to the generic Australian Risk Management standard ISO31000, reference can be made to transport domain standards such as AS 4292 (railways); the functional safety standard AS (IEC) 61508; tunnel specific standards such as NFPA and PIARC; the technological risk analysis standard AS/NZS 3931:1998 and the International dependability standards for failure mode and effects analysis, fault tree analysis, reliability block diagrams and human reliability as well as various defence standards applicable to the safety assessment process.