Risk assessment related tunnels

Following the fire which occurred in March 1999 in the Mont Blanc tunnel located between France and Italy, an Appraisal Committee has been committed to assess the safety of 40 existing French road tunnels, with a length exceeding 1 km. Later, a new regulatory document (circular) was issued (25/08/2000) about the safety of existing road tunnels. In this document, a new procedure is requested : a specific hazards study (SHS). A work is still under progress between different partners to define the methodology to be applied for these SHS. Every SHS will be submitted for acceptance to a National Evaluation Committee. New regulations are under preparation. Such SHS are prepared only after achievements of preliminary studies (traffic studies, rules of operations, specific study for the transportation of dangerous goods if any...) from which a reference state if defined. The different steps of this SHS are : risks identification, definition of scenarios (standardised and customized) from which it is possible to describe a sequence of events, possible consequences and the validity of the system management of the system especially in emergency situations. The conclusion of the study is the evaluation of the safety level with possible use of severity/occurrence matrix. Proposals are then to be made by the contractor and operator to improve the safety level on weak points. Among the difficult issues are : the need for preventive closure of a tunnel when a situation is incidental but without major consequences, the assessment of fire developments for different types of vehicles and the influence of the ventilation, the efficiency of fire fumes extraction, the definition and use of severity/occurrence matrix.