The Tunnel is used to transport items underground for a set maximum distance. This allows for item lines to cross buildings or other item lines. Tier I tunnels are black and trapezoidal, while Tier II tunnels are white and rectangular.
They come in pairs, with each pair consisting of one entry tunnel and one exit tunnel. Tier I tunnel pairs can be placed 5 tiles apart, while Tier II tunnel pairs can be placed 9 tiles apart. This allows them to cross 4 tiles and 8 tiles, respectively.
Like belts, tunnels will not be automatically deselected after being placed. An exit tunnel will be placed if a valid tunnel pair can be formed; otherwise, an entry tunnel will be placed. While placing tunnels, if the location where the cursor is at can form a valid tunnel pair, the potential pair will be shown by a green line.
Because exit tunnels are treated as facing in the opposite direction as their corresponding entry tunnels, placing a tunnel will flip the current building placement rotation.
Each entry tunnel automatically links itself to the nearest in-range exit tunnel of the same type and opposite orientation. Tunnel pairs do not act like teleporters, and instead, they will form a hidden belt track that acts like a regular belt.
Tunnels provide little to no speed advantage when used in replacement of regular belts, but because items are transported underground, less buildings are needed, and the items do not need to be rendered.
Smart Tunnels[]
The Smart Tunnels setting, turned on by default, allows tunnels to automatically delete unnecessary belts when being placed.
A newly-formed tunnel pair will check for and delete a stretch of belts facing the same direction that occupies the entire space between the two tunnels. Smart Tunnels will also delete unnecessary extra tunnels if a potential new tunnel pair stretches past them, allowing for tunnels to be placed via dragging.
The setting only works for exit tunnels and cannot detect both belts and unnecessary tunnels in tandem.
Notes[]
- Both automatic tunnel type selection and smart tunnels can be circumvented with copying and pasting.
- If two entry tunnels point to the same exit tunnel, only the closer one will work.
- Before the Wires Update, no check was performed to see if an exit tunnel has already been linked, meaning that more than one entry tunnel could send items to the same exit tunnel. Additionally, farther entry tunnels were prioritized. This was marked as a glitch.