WP 2 aims primarily at developing cost efficient mitigation measures in case of fire in a tunnel. The focus of the work package is therefore on existing and innovative mitigating systems. In support of this objective, it aims at improving the necessary evaluation tools and at providing innovative new tools where appropriate. Specifically envisaged tools are the mathematical models and the appropriate design scenarios that enable the prediction of hazard conditions. The appropriate design will be based on statistical data and laboratory-scale tests. By providing better knowledge about the fire and explosion hazards involved, design fire scenarios and acceptance criteria will be developed. Fire safety engineering provides the framework for this.