What does the signal aspect of red over flashing yellow indicate?

The signal aspect of red over flashing yellow indicates "Prepare to enter a diverging route at restricted speed." This combination of signals is critical for safety and operational awareness on the tracks. A red signal signifies that the train must stop, while the flashing yellow serves as a warning that the upcoming route diverges.

When encountering a red over flashing yellow signal, the engineer must be prepared to stop in a controlled manner because the red signal mandates a stop. The flashing yellow indicates that the train will be required to proceed on a diverging route, which often involves navigating a switch or turnout. Proceeding under these circumstances means doing so at restricted speed, which allows for the necessary precautions to ensure safe passage through a potentially complex track configuration. This signal setup is essential for ensuring that operators understand the need to reduce their speed significantly when approaching the diverging route to avoid accidents or derailments.

In contrast, options that suggest proceeding at full speed or that the route is clear would not align with the meanings of the red and flashing yellow aspects, which are designed to enforce caution and preparedness for changes in track direction.