Ventilation during road tunnel emergencies

A review has been undertaken of the requirements and advice on ventilation during road tunnel emergencies, contained in the standard BD 78/99 'Design of Road Tunnels' and the draft standard TD 43 'Limited facility grade separation'. The study has involved evaluating published literature, consultation with other organisations involved in this field, assessing key technical issues, and preparation of recommendations. All factors that are relevant for the design and operation of tunnel ventilation systems have been considered. A set of standardised vehicle fire scenarios and a framework for risk-based design have been proposed. A key objective is to ensure better consistency between tunnel designs and with current international best practice. The proposed framework is capable of supporting key decisions such as the choice of design scenario for a particular tunnel and the selection and justification of the ventilation configuration. Improved design guidance is given on minimising smoke spread between bores and defining ventilation systems with extract capability. New guidance is proposed on ventilation analysis, covering the choice of ventilation model and modelling strategies, the expertise required by the user, and the interpretation and reporting of results. Better guidance is also given for operations and emergency response. This covers the roles and responsibilities of the tunnel operator and the fire brigade, and the selection of ventilation responses. A key aspect is the need for pre-defined ventilation plans, which can be used without delay by the tunnel operator.(A)