Tunnels form microcosms in which you can find equipment for operations and precautions in case of emergencies. The superstructure, which refers to the track bed on which the tracks are mounted, is responsible for safety transporting trains weighting over 160 tonnes.
It also absorbs the sound of the trains.
You can identify the method used to build the tunnel by looking at the shape of the cross-section: if it is circular, it was created by a tunnel boring machine.
If it is slightly asymmetrical, it was excavated using the New Austrian Tunnelling Method.
The inner workings of a tunnel
Equipment for operations and precautions for the elevated underground lines (left, station U2 Seestadt) and for the cut-and-cover tunnelling method (right, station U2 Volkstheater)