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Centralized traffic control (CTC) 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.
Railway signalling (BE), or railroad signaling (AE), is a system used to control the movement of railway traffic. Trains move on fixed rails , making them uniquely susceptible to collision . This susceptibility is exacerbated by the enormous weight and inertia of a train, which makes it difficult to quickly stop when encountering an obstacle.
CBTC is a signalling standard defined by the IEEE 1474 standard. [1] The original version was introduced in 1999 and updated in 2004. [1] The aim was to create consistency and standardisation between digital railway signalling systems that allow for an increase in train capacity through what the standard defines as high-resolution train location determination. [1]
Standards for North American railroad signaling in the United States are issued by the Association of American Railroads (AAR), which is a trade association of the railroads of Canada, the US, and Mexico. Their system is loosely based on practices developed in the United Kingdom during the early years of railway development. However, North ...
Track circuits transmit train locations to distant control centers and data links allow direct manipulation of the points and signals. While some railway systems have more signal boxes than others, most future signaling projects will result in increasing amounts of centralized control relegating the lineside signal box to niche or heritage ...
Interoperable Communications Based Signaling (ICBS) is an initiative backed by the Federal Railroad Administration to enhance interoperability and signaling procurement in the railway system of the United States by creating a single national standard for train control and command systems. The concept was launched in 2005 and an interoperable ...
Signals are most commonly mounted on trackside masts about 12 to 15 feet (3.7 to 4.6 m) high to put them in the eyeline of the engineer. Signals can also be mounted on signal bridges or cantilever masts spanning multiple tracks. Signal bridges and masts typically provide at least 20 feet (6.1 m) of clearance over the top of the rail.
The units are connected to a central control computer by internet. The central computer conducts a "census" of keys before releasing a solenoid and freeing a key for the required section of track—an engraved tag identifying the respective section of track is securely attached to the relevant key.