rail traffic signal
Automated or remotely controlled signals displaying or broadcasting changing commands to trains and other rail traffic.
Rail traffic signals are lights, mechanical flags, audio speakers, or other forms of signage which display or broadcast dynamically changing commands to rail traffic, including trains and subways. As a purely automated or remote-controlled signal, this differs from manned rail traffic control stations which are usually buildings.
The signal communicates a command to rail traffic and can use light, mechanical movement, or sound. Its operation is automated or remotely controlled.
A staffed rail traffic control station houses people directing railway movements. The signal is the command-displaying device, even when a controller operates it from that station.
