## 3 Railway Traffic Control Systems  
In terms of implemented functions, RTC devices can be divided into interlocking and line devices, as well as level-crossing signalling devices. They differ in terms of execution technology, starting from mechanical, through relay electric and then computer based [41]. This research paper focuses on interlocking devices as the most functionally developed, and the execution technology does not impact the application of the proposed method. Railway traffic control devices are employed to ensure railway traffic security and efficiency [42; 43; 44; 45]. Technology development entailed a change in the manner of implementing setting functions, entering commands and visualizing the traffic situation and device condition [46]. Key-operated equipment requires a proper points key that depends on the turnout position, which after placing in the combiner enables removing a signal key and setting the signalling device in the \"proceed\" position. Mechanical transmission devices were next to develop. Their operating principles involve physically blocking the possibility to switch the points or semaphores. Electric drives and signalling devices were developed by applying electromechanical engineering practices, which combined interlocking functions with the possibility of actuator control. The appearance of relay devices entailed the development of new functions associated with the visualization of the traffic situation, equipment status and command entering, as well as interlocking function separation [47]. In the case of computer-based devices, these functions have been clearly separated and implemented by appropriate layering. When analysing the conditions that the discussed devices must meet, one can conclude that all devices involve an interlocking system, wherein any action is most often based on information from occupancy monitoring systems. Examples of such systems are track circuits, axle counter systems or elements with a point-based operation nature--wheel/axle/train sensors. All devices implement safe train travel conditions in a dependent manner, i.e., meeting specified requirements is monitored with the use of devices designed for this purpose. Displaying a proceed signal in interlocking station devices is possible only in the case of satisfying route setting conditions within a given control area, whereas in the case of automatic line devices, safe train traffic is managed by separating them with an appropriate free route section that may be constant (constant block section) or variable, depending on the rolling stock traction features and speed (floating block section). Interlocking devices at stations constitute the most extensive system in functional terms. This arises from the nature of the implemented operations and the extensive track system. They execute train route and shunting settings under normal conditions and, sometimes, in the case of faults or disturbances. A train's movement is based on the proceed on sight authority (PoSA) signal, which can be displayed virtually without taking into account all dependencies (besides the W24 indicator) or on a written order, at the full responsibility of an operator. A block system implements only train movement (shunting is implemented only within posts), securing train traffic through displaying appropriate signals on block signals, depending on the traffic situation along the route, based on information from occupancy monitoring systems. A railway traffic control system is a set of control and controlled devices (elements), with its operating range covering a specific control area. These devices form the technical structure of a control system, and their interconnections constitute an RTC system functional structure. A system structure is unique for each control area. Elements are controlled using strictly defined control algorithms.