The BasicsEditTunnel blocks face the direction they are placed with a flat concrete back and a dark “tunnel” face. Tunnels can span either 2 blocks, 1 block, or zero blocks. For a tunnel to function correctly you must have and input tunnel and an output tunnel facing away from each other. Input and output tunnel blocks need a transportation block (conveyors, etc) connected to the tunnel block face, the transportation block connected to the tunnel block determines if it is an input or output tunnel. Therefore the required area to build a tunnel would be 1x 6 maximum and 1 x 4 minimum.
Conduit Junction:EditThis is an important way to use tunnels because there is no other way for a conduit and a conveyor to cross paths.
Avoiding Router:EditRouters are very useful blocks. Sometimes you may want to limit what conveyors a router can feed to in a tight space, like in the middle of other conveyors. One strategy for this issue is to use tunnels to avoid the router or other similar outputs.
These tunnel builds can be invaluable for their special behavior. The principle that these builds function on is that a 0 span tunnel can fit inside of a 2 span tunnel sharing one of the tunnels for a 3 tunnel block build. The knowledge that tunnels could be used in this way was posted by Anuke themself in the Mindustry discord.
By using a 3 block tunnel build with two outputs you get a kind of splitter (like a router) but with special priority behavior. Items will flow into the single input tunnel and will feed the first output tunnel block. If this conveyor line becomes full the items will feed the second output tunnel block. With this build you can assure a conveyor line is always full without clogging your item flow. An example would be for use in feeding iron to a smelter when you still want extra iron to “overflow” to your core.
By reversing the overflow tunnel build with two inputs and one output you get merging behavior that is slightly better than the T merge. If enough items are input this build will output items faster than a pulse conveyor can move items away.
This example tunnel build is just two normal 2 span tunnels overlapping. This can create a two-way conveyor for those moments when you are really out of space.