Tunnels are an easy way to avoid high pitches and rivers. They are used for several kinds of surface transport.
The tunnels once were built using techniques known from mining. Miners dug the tunnels like they built their mine adits before. The earliest tunnels were built using various shafts along a line and staring into both direcions at the sole. This technique is used until today, the new Gotthard tunnel is built this way at the moment . But modern technology also provides new techniques for the construction of road tunnels. Huge drilling machines drill into the rocks, transport the material away, use some of the rocks and additional material like cement to produce concrete, support the ceiling with a hydraulic system which also forms the mould for the concrete. Such tunneling machines are somtimes a hundred meters long and at their end the tunnel is almost complete. They produce the tunnel while moving forward.