What does an illuminated "S" at a Subdivision "A" signal indicate?

An illuminated "S" at a Subdivision "A" signal serves as an important indicator for operators, specifically notifying them that there is a switch control ahead. This is crucial for train operators as it prepares them for the necessary adjustments in their approach to the track. An illuminated "S" alerts them to the presence of track switches, which must be navigated correctly to ensure the safety and efficiency of rail operations.

Recognizing this signal allows train operators to remain vigilant and prepared for any track changes they may need to execute. This preparation is essential in maintaining orderly train movement and preventing potential collisions or derailments associated with improperly managed switches. Understanding the function of this signal is key for effective train routing and operational safety.