In what situation would 14L not be sounded in a Quiet Zone?

In a Quiet Zone, the primary purpose is to minimize noise from train operations, particularly the sounding of horns at crossings. The correct situation in which 14L would not be sounded is when exceptions are specified by Special Instruction. This means that there may be specific conditions or designs implemented in particular areas of the Quiet Zone that allow for the sounding of the whistle as needed for safety purposes, despite the general guidelines meant to reduce noise.

Special Instructions are often enacted to ensure safety and compliance with unique local regulations or conditions that may not align with standard operational procedures. Thus, the determination of whether or not to sound the whistle in a Quiet Zone is ultimately governed by these additional instructions that pertain to specific circumstances.

In contrast, the other options do not account for the nuances of operational safety and local regulations. The absence of trains or undergoing maintenance might suggest a quieter environment but does not provide the same regulatory backing that Special Instructions do regarding when a whistle would be essential for notifying personnel of train movements, regardless of the surrounding conditions.