Certain locations are permitted to allow more than one train into a single section, e.g. to join trains or enable 2 trains to use one platform.
The movement of the second train into an occupied section is by setting a "call-on" route. The call-on can be from a shunt signal or as a subsidiary to a main signal . In either case the call-on aspect is approach released which should ensure the approaching train is running at a slow speed (15mph) to mitigate collision damage.
In some boxes a track circuit override also needs to be activated before the signal will clear.
See also Huddersfield Control
Last edited by GeoffM on 15/09/2016 at 03:00