Road tunnel safety levels and minimum operating requirements

摘要

A concept and process for the definition of minimum operating requirements (MORs) is presented, following the key principles that the MOR is applied to the Safety Functions, rather than to specific items of equipment or systems, and the MOR is considered to reflect the minimum level of safety accepted by tunnel users so if the tunnel is below its MOR then it should not normally be open to traffic, without mitigations. Little guidance exists for the derivation of MORs. The process is complex because of the scale of systems and procedures required for the safe operation of road tunnels and the inter-dependency between those systems and procedures. When a piece of equipment, a system, procedure or other element of the tunnel operating condition fails or degrades, the impact on safety is not always clear and judgement is often required, resulting in the potential for uncertain or inconsistent outcomes. Discussion is presented on the current tunnel safety landscape to provide context for the discussion of the benefits and principles of MORs. A practical example of MOR application is presented, showing how compensatory measures may be deployed to enable continued safe operation of a tunnel with degraded systems.