What is the name of the signal aspect represented by yellow over lunar?

The signal aspect represented by yellow over lunar indicates "Approach Restricting." This aspect is typically used to inform train crews that they should prepare to slow down and be prepared to stop at the next signal while also indicating that the track ahead may be occupied, potentially indicating a restriction such as a work zone or other conditions that require caution.

Under GCOR rules, the lunar light signifies a clear indication of a restrictive condition, prompting engineers to maintain a cautious speed and be ready for any upcoming operational changes. Recognizing the significance of this signal aspect is crucial for safe and effective railway operations, as it directly relates to the movement of trains in proximity to signals regulating train speed and track conditions.

The other options do not accurately reflect the meaning of this signal aspect. For instance, "Stop" would require a different configuration altogether, while "Clear" and "Diverging Clear" indicate more favorable conditions for train movement. Understanding the nuances of signal aspects, like yellow over lunar, is essential for ensuring safety and compliance on the railroads.