page_title: Centralized traffic control
section_title: Operation
hierarchical_section_title: Centralized traffic control / Operation
caption_attribution_description: English: Antwerpen-Noord signal box, during an open day visit. The system shown is EBP (Elektronische Bedien Post), made by Siemens. Nederlands: Seinhuis in Antwerpen Noord, tijdens een open dag.
context_page_description: Centralized traffic control is a form of railway signalling that originated in North America. CTC consolidates train routing decisions that were previously carried out by local signal operators or the train crews themselves. The system consists of a centralized train dispatcher's office that controls railroad interlockings and traffic flows in portions of the rail system designated as CTC territory. One hallmark of CTC is a control panel with a graphical depiction of the railroad. On this panel, the dispatcher can keep track of trains' locations across the territory that the dispatcher controls. Larger railroads may have multiple dispatcher's offices and even multiple dispatchers for each operating division. These offices are usually located near the busiest yards or stations, and their operational qualities can be compared to air traffic towers.
context_section_description: Although some railroads still rely on older, simpler electronic lighted displays and manual controls, in modern implementations, dispatchers rely on computerized systems similar to supervisory control and data acquisition (SCADA) systems to view the location of trains and the aspect, or display, of absolute signals. Typically, these control machines will prevent the dispatcher from giving two trains conflicting authority without needing to first have the command fail at the remote interlocking. Modern computer systems generally display a highly simplified mock-up of the track, displaying the locations of absolute signals and sidings. Track occupancy is displayed via bold or colored lines overlaying the track display, along with tags to identify the train (usually the number of the lead locomotive). Signals which the dispatcher can control are represented as either at Stop (typically red) or "displayed" (typically green). A displayed signal is one which is not displaying Stop and the exact aspect that the crew sees is not reported to the dispatcher.
caption: Computer-based controls for a modern electronic interlocking
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