When can a train use a secondary track in the reverse direction without permission?

A train can use a secondary track in the reverse direction without permission in an emergency situation. This is critical because emergencies can arise unexpectedly, such as a failure of the primary track, technical issues, or any incident that poses an immediate risk to safety. The rules prioritize the safety of passengers and crew, allowing for the immediate need to divert trains to avoid accidents or further complications.

In contrast, the other scenarios, like maintenance work or scheduled service, require specific permissions and procedures to ensure safety and efficiency. Using a secondary track for maintenance typically involves planned operations that need coordination with dispatch and adherence to established protocols. Similarly, during scheduled service, trains must follow designated routes as planned, ensuring consistent and safe operations. Adverse weather conditions also warrant caution and specific protocols, but they do not automatically allow for reverse movement on secondary tracks without prior approval. Thus, the emphasis in emergencies is on rapid response and safety, justifying the allowance for such action without needing additional permission.