Road tunnel risk-based safety design methodology by GU@LARP Quantum risk model

The ALARP concept is used in different countries for different sectors of activity where a risk assessment or measure is requested. In this paper a model is developed based upon ALARP principle for tunnel risk-based design in case of fire accident scenarios. In Italy, ALARP risk acceptability and tolerability criteria have been adopted then the compliance with them has to be verified in order to guarantee a minimum-sufficient level of safety. The quantum of risk coupled with any design scenario is defined and modelled and the consequent individual quantum of risk coupled with the single exposed unit in the scenario is defined too. The methodologies for the identification of the requested design scenario, in number and type, are outlined. The scenarios are described in a shape suitable as INPUTS in the thermo-dynamical numerical simulations for fire generation and exposed units evacuation. The expected OUTPUTS of the numerical simulation are the estimations of the number of the fatalities (N) coupled with the single specific scenarios. In parallel with the above physical deterministic scenario simulations, a conceptual and operational procedure has been also established for the scenarios probabilities assessment. Merging the resulting data of both the above separate models, the risk quanta Gu@larp model is finally established. A case study is developed considering scenarios related to a virtual limit tunnel to support the description of the model itself, properties, advantages and perspectives.