Railway block safety systems make part of the safety and signaling systems for railway transports, which also include train control systems, train traffic systems, and wireless communication devices. The necessity for such systems arose from the fact that trains are much heavier than road vehicles, requiring a much larger breaking distance to come to a complete halt (Takashige 2019). At the same time, only one train can occupy a part of the railway at any given moment. The section occupied by the train is called a block. The system works by making a train circuit to shorten out whenever a train crosses it, allowing detection of a train on a block.
In addition to locating the train and giving out signals to other participants in the traffic, the system ensures that trains comply with rules and regulations assigned to a specific block. The train is put under surveillance and is required to comply with the speed limit. If it goes too fast – emergency breaks will activate and force the train to either slow down or go into a complete halt (Takashige 2019). The primary actor in this scenario is the train driver, who has to follow the signals provided by the system. If the signal warns him of danger, the speed must be reduced to zero, before any hazard is removed and it is safe to proceed. Once the light returns to green, they may continue (Takashige 2019). Since the system is automated, there is no actor operating it. In rare instances where the system is not operated by a machine, the driver has to comply with the signals of a human regulator.
Reference
Takashige, T. (2019) ‘Signaling systems for safe railway transport’, Japan Railway and Transport Review, 21, pp. 44-50.