What should a operator do upon seeing a YELLOW OVER YELLOW signal?

A YELLOW OVER YELLOW signal indicates that the operator must proceed with caution while being prepared to stop. This signal serves as a warning that there might be a condition ahead that requires the operator to reduce speed and be alert to any potential hazards or changes in the operating environment. The operator should remain vigilant and ready to respond to any subsequent signals or conditions that may require stopping or slowing down further.

In contrast, other options suggest actions that are not appropriately cautious in this context. For example, proceeding at full speed does not account for potential risks ahead, while stopping immediately could disrupt operations unnecessarily. Proceeding normally on the main route without caution disregards the warning indicated by the yellow signals. Therefore, understanding the appropriate response to a yellow signal is crucial for safe and effective tower operations.