What is the maximum speed permitted if a speed indicator on a controlling locomotive fails enroute?

In the event of a speed indicator failure on a controlling locomotive, the maximum speed permitted is typically the normal track speed. This standard assumes that operational safety is maintained under the given circumstances.

When a speed indicator fails, the crew is trained to operate consistently with the known parameters of the track. Operating at the normal track speed allows the train to maintain predictable and safe speeds while ensuring compliance with the established guidelines unless otherwise specified by local rules. The normal track speed is designed to ensure safe operation under various conditions.

Other options like half the normal track speed or local guidelines may feel conservative in nature, but they do not align with industry practices that prioritize safe, effective train handling based on established limits unless there is a specific directive to reduce speed. The highest legal limit known to the operating crew from prior training and knowledge of the train's capabilities ensures a balance of safety and efficiency, making normal speed the logical choice.