There are different methods for building an underground tunnel.
These depend on how deep the line is, the soil it passes through and whether there are any buildings on the surface above.
If the line travels at a shallow depth along a road or through an undeveloped area, it can be excavated from above using the cut-and-cover method.
This method will only be used to a limited extent for the new U2/U5 underground lines due to the level aboveground development: only for station buildings and for a section along Landesgerichtsstraße.
In all other cases, either a tunnel boring machine (affectionately known in Vienna as the ‘mole’) will be used or the New Austrian Tunnelling Method.