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In Track Warrant Control, or TWC, the train dispatcher issues "track warrants" via radio that authorize the train between two specified limits. The limits are often mileposts or stations. The track warrant may authorize a train to proceed to a station and "clear the main", or enter a siding so an oncoming train can pass.
There are two main types of signaling aspect systems found in North America, speed signaling and weak route signaling. [citation needed] Speed signaling transmits information regarding how fast the train is permitted to be going in the upcoming segment of track; weak route signaling transmits information related to the route a train will be taking through a junction, and it is incumbent upon ...
In double track territory one may find two signals mounted side by side on a bracket which itself is mounted on a post. The left hand signal then controls the left-hand track, and the right signal the right-hand track. A gantry or signal bridge may also be used. This consists of a platform extending over the tracks; the signals are mounted on ...
Signals in CTC territory are one of two types: an absolute signal, which is directly controlled by the train dispatcher and helps design the limits of a control point, or an intermediate signal, which is automatically controlled by the conditions of the track in that signal's block and by the condition of the following signal. Train dispatchers ...
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.
Unlike ordinary signals, there may be a series of identical signals installed along the track so that at least one is always visible to the train driver at any time. All signals in the same group display the same indication simultaneously. A 'stop' indication means "stop immediately", even if the train is not at the signal. The signals can also ...
A rail break between the insulated rail joint and the track circuit feed wiring would not be detected. Failure modes that result in an incorrect "track clear" signal (known usually in North America as a "false clear") may allow a train to enter an occupied block, creating the risk of a collision. Wheel scale and short trains may also be a problem.
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 ...