What does the Minimum Allowable Level (MAL) indicate when approaching a failed signal?

The Minimum Allowable Level (MAL) is an important safety parameter indicating the lowest acceptable operational threshold for a signal in scenarios where signal failure occurs. When the MAL reflects a red signal, it serves as a clear warning of impending danger or critical malfunction, signaling operators that immediate action needs to be taken to address the issue. This red indication is crucial for maintaining safety protocols and ensuring that the situation is managed effectively to prevent further complications.

In this context, the other options do not accurately represent the purpose of the MAL in the operational landscape. A green signal would imply that conditions are normal and safe, while a flashing yellow might suggest caution but does not denote a failure situation. An indication of no change fails to communicate any urgency or the requirement for intervention in the face of a failing signal, thereby making it less effective in ensuring prompt corrective actions.