Rail tunnels risk analysis: the UNIFI approach

The Italian standard on Rail tunnel safety issued in 2005 identified the minimum safety requirements for each type of rail tunnel. This standard introduces two types of risk analysis (base and extended) to be performed in order to verify the fulfilment of all safety requirements and to compare the tunnel risk level with fixed acceptability thresholds. A methodology to conduct an extended risk analysis was developed at the University of Florence in order to evaluate heat and toxic gasses concentration, their diffusion and their effects on passengers in function of infrastructure, train and fire characteristics and evacuation procedures. The proposed methodology allows to account for tunnel geometric characteristics (section and sidewalks number and width), vehicle characteristics (type of train and number of passengers) and fire event conditions (heat release rate, heat release rate time development, toxic gasses type and concentration). The application of this methodology allows to estimate the saving people likelihood and the number of expected deaths as a function of the distances covered by each passenger depending on different accident scenarios and on evacuation procedures such as scheduling of door openings and tunnel characteristics and safety measures available. The applied methodology has been proven highly useful as a design tool in order to identify the best design, construction and management options to increase safety levels. It could also be used to define the most effective evacuation procedures for each emergency scenario (A). For the covering abstract of the conference se ITRD E216739.