In the late '90s, the tunnel safety issue was dramatically raised by a number of tragic fire events in road tunnels, such as Mont Blanc Tunnel (1999, 39 deaths), Tauern Tunnel (1999, 12 deaths) and San Gotthard Tunnel (2001, 11 deaths). After these events, an increased attention has been paid to the safety of tunnel users by road agencies, industry and research community.
Several regulation codes and guidelines have been issued, often motivated by a European Union Directive (EU 2004/54/CE) which prescribes the minimum safety requirements for EU tunnels. These requirements involve structural solutions (cross-section geometry, emergency exits, lay-bys, etc.) as well as non-structural systems (ventilation, lighting, water supply, monitoring, road signs, etc.).
For the (frequent) case in which all the aforementioned requirements cannot be satisfied at a reasonable cost, the EU Directive allows for the implementation of alternative safety measures. A quantitative assessment of tunnel safety is prescribed to demonstrate that the alternative measures result in equivalent or improved protection. The recommended assessment tool is a risk analysis performed by an independent specialist, taking into account all the structural and non-structural features of the given tunnel as well as traffic flow and composition.
In this conference, we present the main features of a risk analysis procedure, referring to the experience gained through the safety assessment of several new and existing tunnels. The procedure involves the use of multidisciplinary tools, including: traffic analysis for the identification of the frequency of initiating events; event tree analysis for the definition of accident scenarios with their probability; 3D computational fluido-dynamics for the simulation of smoke propagation; evacuation modeling to evaluate the number of victims.
Carlo Callari, University of Molise, Italy