colour-light signal
Quick Summary
Color-light signals are a modern type of railroad signal that use powerful electric lights to display information to train crews. These signals typically use red, green, and yellow lights, which can be displayed individually or in combination. Red universally signifies stop or danger, green means the track is clear, and yellow indicates a warning. While these basic meanings are consistent worldwide, specific combinations of colors can convey different instructions depending on the railway system. Color-light signals have largely replaced older systems like semaphores and are now standard on most major railways globally.1
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