Which signal requires immediate reduction of speed for trains exceeding Medium Speed?

The signal that requires an immediate reduction of speed for trains exceeding Medium Speed is the Approach Sign. This particular signal indicates to the engineer that a more restrictive signal is ahead and prompts them to reduce their speed to prepare for a possible stop or to comply with the upcoming signal's requirements. It is essential for maintaining safety and ensuring that trains can stop in time if necessary.

The need for immediate action stems from the fact that the Approach Sign serves as a critical indicator of upcoming conditions that may not be compatible with high speeds. By adhering to the instruction to reduce speed, the locomotive engineer helps to prevent potential accidents caused by running through signals at excessive speeds.

Other signals, while important, do not specify an immediate speed reduction in the same way as the Approach Sign. Instead, they may indicate general operational guidelines or other speed conditions, but they do not carry the urgent directive that an Approach Sign provides. Understanding and recognizing the significance of the Approach Sign is vital for safe train operation, particularly in areas with variable speed limits or where signal compliance is crucial.