Rail signal

A rail signal is a basic train control device used to divide rail networks into blocks and regulate when trains may enter them. It is one of the core tools for building safe rail junctions and separating tracks so that multiple trains can share the same system without colliding. By default, signals are placed on the right side of the track and allow travel in that direction; this can be changed in the options. An automatic train will not enter a block that has signals only on the left side. If two signals are placed directly opposite each other, trains may travel in both directions through that point. When holding a rail signal, the game highlights the position directly opposite an existing signal in white.

Rail signals have four visible states. A green signal means the monitored block is empty. A yellow signal means a train cannot stop before the monitored block and will continue through the signal; in this case the block is already reserved for that train, and every other entrance signal to that block turns red. A red signal means the monitored block is occupied, or another signal monitoring that block is already yellow. A blinking signal indicates that the signal is not placed on a rail, or that the block being monitored is the same as the block before the signal. When a signal is red, locomotives stop before it. For earlier stopping behavior, a rail chain signal is used instead, since chain signals mimic the state of the next signal in front of them.

Rail signals can also be integrated with the circuit network. A circuit condition may be configured so that, when it becomes true, the signal is forced red. In addition, the signal can output circuit signals corresponding to its green, yellow, or red state. If the signal is red because of a circuit condition, it does not output a circuit network signal.