Token (railway signalling)
In railway signalling, a token is a physical object which a train driver is required to have or see before entering onto a particular section of single track. The token is clearly endorsed with the names of the section to which it belongs. A token system is more commonly used for single lines because of the greater risk of collision in the event of a mistake being made by a signaller or traincrew, than on double lines.
A token being offered by a signalman on the Keighley & Worth Valley Railway
Examples of single line tokens: Tablet on left, key token on right
One Train Only token used by Indian Railways
Electric staff instruments manufactured by Webb and Thompson
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. In the UK, the Regulation of Railways Act 1889 introduced a series of requirements on matters such as the implementation of interlocked block signalling and other safety measures as a direct result of the Armagh rail disaster in that year.
A Class 66 locomotive (right) is waiting at a red signal while a First Great Western passenger train (left) crosses its path at a junction.
A block signal and a 130 km/h speed limit at kilometer post 547 in Iisalmi, Finland
Short signal blocks on the Toronto Transit Commission subway system. A train (not visible) has just passed the most distant, leftmost signal, and the two most distant signals are red (stop and stay aspect). The next closest signal is yellow (proceed with caution), and the nearest signal shows green (proceed).
Traditional mechanical signals on display at a railway station in Steinfurt, Germany