Visual indication passed to a train driver to advise the speed, direction or route of the train. There are almost as many types of signals as there are railways but they fall into the following main categories:
- handsignals - used mainly where there are no fixed signals or where the fixed signalling has failed. Generally, each railway has its own defined handsignals recognised by its operators.
- semaphore signals - a fixed lineside signal where the stop indication is displayed as a horizontally positioned arm and proceed as a 45º or vertical arm.
- colthe light signal - a fixed lineside signal showing light indications to drivers.
- cab signals - where the indications are displayed in the driver's cab.