What term describes the appearance of a fixed or cab signal?

The term that describes the appearance of a fixed or cab signal is "signal aspect." In railway terminology, the aspect refers specifically to the visual representation of a signal, which conveys to the train crew the status or instruction related to the operation of the train. This could include conditions such as whether to proceed, reduce speed, or stop.

Understanding signal aspect is crucial for safe train operations, as different aspects will indicate different commands that the crew must follow. Each aspect is designed to be easily recognizable and conveys important operational information clearly to ensure adherence to safety protocols while in motion.

In contrast, the other terms do not accurately represent what is being described. For example, "signal indication" could suggest a broader meaning that encompasses various interpretations of signal behavior without specifically referencing the visual state. "Signal reasons" does not relate to the visual appearance of signals at all, while "signal position" refers more to the physical location of the signal rather than its visual indicators. Thus, the term "signal aspect" is the precise definition needed in this context.