Safety measures

Following the integrated approach for the planning of a (sufficiently) safe tunnel system  design and operation of a tunnel has to comply with minimum safety requirements. Further, alternative or additional safety measures may be required for various reasons, like for instance:

• to counterbalance the influence of specific risk increasing factors, like frequent congestion in a urban tunnel or a high gradient exceeding a defined reference value
• to compensate shortcomings in the construction or the equipment of an existing tunnel, for instance in the course of an upgrading process

The decision whether or not additional safety measures are required, can be based on a prescriptive as well as a risk-based approach

In general, safety measures can be grouped into 4 categories, according to their mode of action and their main effects on risk:

• Measures preventing the occurrence of significant incidents – thus reducing their frequency
• Measures mitigating the consequences of significant incidents
• Measures supporting self-rescue
• Measures supporting emergency response.

Measures may concern tunnel structure or tunnel equipment, as well as procedures for tunnel operation or emergency response. If the transport of dangerous goods is authorized in a tunnel specific measures may be required. Any additional safety measure needs to be integrated into the existing complex safety system of a tunnel in the best possible way, taking all relevant interaction effects into account.