Tunnels and underground networks

Tunnels are useful to pass hills or mountains and also to build underground networks or undersea tunnels.

Select the tunnel tool and click on one of the extremity of the future tunnel, is the both facing extremities allow the construction of a tunnel entry, the tunnel is built :

As seen in the tutorial Settings and interface there are two ways to see under the ground. To have a global looking at the underground networks, it's better to use the normal underground view keyboard shortcut “shift+u”, to build easily an underground network in one or more layers you'd better use the layer sliced view :

It's possible to build just a tunnel entry instead of a complete tunnel by holding down ctrl key while building :Then the underground constructions are the same as ground's ones but instead of using a way tool you have to use the tunnel tool which works the same way :

Then you can build stations, signals and electrifications as you want.

To make an underground slope, use first the adapted artificial slope tool on a way extremity to make a down or up slope.Then vary the height of the layer sliced view to go to the lower or higher layer and extend the network.

You can build undersea tunnels by the same way but of course you have to take care of the sea deepness : more the sea is deep and more the tunnel must be deep.