What is the maximum speed allowed if the horn or whistle fails?

The maximum speed allowed when the horn or whistle fails is set at a specific limit to ensure safety in operations. In this context, 30 MPH is the correct speed limit because it provides a balance between maintaining operational efficiency and ensuring safety. The regulation acknowledges that the horn or whistle is a critical signal device for communicating with other trains and personnel; its failure likely indicates a more cautious approach is necessary.

While higher speeds can be more convenient, they come with increased risks, especially in situations where audible signals are not available for warnings or announcements. Therefore, the limit of 30 MPH serves to mitigate potential hazards that could arise from the lack of auditory signaling, promoting safe train movements under compromised conditions.