Ventilation and Distance of Emergency Exits in Steep Bi-directional Tunnels

Experience from occurrences of fires in road tunnels shows that victims are usually found within a few hundred metres of the scene of the incident. The fatal consequences of a fire in a tunnel measuring only a few hundred metres can be comparable to those resulting from a fire in a long tunnel. In tunnels with considerable slope the hazard for tunnel users increases due to rapid smoke dispersion. In addition to an efficient alarm system, successful self-rescue requires tunnel users to be provided with measures that enable them to reach an emergency exit. When it comes to short, steep, bi-directional tunnels, the aerodynamic approach to avoiding or slowing down smoke dispersion reaches its limits. Longitudinal ventilation systems can cause additional danger by worsening visibility conditions. The largely passive safety system consisting of a parallel safety gallery featuring short distances between emergency exits promises great benefits in terms of safety in these particular constructions. But even here, the question is raised as to determining an appropriate distance.