What indicates that a signal is showing a Restricted Proceed?

Answer: B — number plate is present

A Restricted Proceed signal is indicated by the presence of a number plate attached to the signal. This number plate usually contains a specific number that corresponds to the speed limit authorized for the train to proceed under restricted conditions. The presence of the number plate serves as a critical visual cue for conductors and engineers, ensuring that they can safely navigate the track while adhering to speed restrictions or other operational guidelines that may be in effect due to track conditions, emergencies, or scheduled work. The other indicators mentioned do not specifically signal a Restricted Proceed. For example, signal lights that stay steady may indicate other types of operational statuses, while a horizontal signal arm typically represents a complete stop. The display of two red lights also signals a stop, which is not consistent with the concept of a Restricted Proceed, where the train is allowed to move but with restrictions. Understanding these nuances helps train crews maintain safety and efficiency in their operations.