On November 11, a confirmed number of 159 people died after fire broke out in the Kitzsteinhorn fenicular railway tunnel near the ski resort of Kaprun, Austria. The tragedy has been described as Austria’s worst ever accident and looks certain to once again throw the spotlight on tunnel safety following last year’s fatal fires in the Mont Blanc and Tauern Tunnels.

Currently there is no indication as to the cause of the fire. Austrian police are holding an investigation into the tragedy that will be followed by a thorough technical inquiry.

The inquiry looks certain to focus on the possible sources of ignition of the fire, currently thought to be friction, and the nature of the flammable material on or within the train that was said to be un-burnable. The lack of the safety systems will also be questioned given the virtual impossibility of external rescue during a fire event within the mountain tunnel.

The train had stopped following the discovery of the fire some 600m into the 3.3km long tunnel.The passengers were unable to open the doors, apparently controlled by the train attendant, effectively trapping them inside the train.

Only 12 people escaped the inferno by breaking the back window of the train, climbing out and making their way down the 800mm wide inclined metal staircase at the side of the track. As the tunnel was open at both ends there was a substantial chimney effect with air drawn in from the lower portal feeding the combustion process. Railway workers who entered the tunnel after the fire report that the train’s base is all that remains following the intense heat of the fire that reached 1000° C.

The train carriages are a close fit to the tunnel cross-section. A haulage rope arrangement pulls the rolling stock up the incline. As one train goes up, an empty train comes down with a central passing place within the structure.

Construction of the tunnel started in 1970. The JV of ÖSTAG/ Hochtief /Gerwerkschaft Walter/Thyssen Schachtbau used a 4.2m diameter DEMAG TBM to drive the 3.3km long, 40° inclined tunnel that opened in 1974.