The interlock equipment has supported the safe train operations of today as a device for controlling the operation in the safe station premises. This paper surveys interlock device’s transition from mechanical signals to today’s electronic signaling devices and analyzes how security mechanisms have evolved. It shows that safety has been supported by the notion of fixed block system, in which only one train is allowed to travel in one route. In addition, this paper discusses the realization of moving block suitable for Communication Based Train Control era and proposes a new interlock table. Unified Train Control System (UTCS) is introduced as an implementation example, and it is shown that the UTCS is an IoT-era train control, which realizes simplification of the interlock function itself and flexible and safe control by exchanging information between the central processing unit and the point machine, the level crossing device and the train.
CBTC, interlocking equipment, moving block, railway signaling, train control
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