Signal Boxes are important structures on a railroad that are used by signallers to control signals, points and the communication with other signal boxes. They ensure the safe and efficient movement of trains across the network.
While most of the signal boxes in the game are dedicated to a specific station and surrounding area, Marigot Crossing Signal Box and Benyhone Loop Signal Box are an exception for that, controlling a crossing and a passing loop respectively.
All signal boxes have an XP requirement. As you play the game, you gradually gain XP and therefore gain access to more signal boxes over time. Glassbury Junction Signal Box is currently the only signal box with the lowest XP requirement, currently being 750 XP. In contrast, Dovedale Central Signal Box and Cosdale Harbour Signal Box has the highest requirement, currently being 7500 XP.