Under what condition do Form L's become void?

Form L's, which are instructions or requests for train operations, become void under specific circumstances. One primary condition is when a new timetable goes into effect. This is because a new timetable can introduce changes to train schedules, routing, and operational procedures, which would render any prior instructions outlined in the previous Form L obsolete. Therefore, any adherences to earlier instructions would need to be reassessed and updated according to the new rules and schedules.

The other scenarios presented do not typically nullify Form L's. For example, when a train stops, it may still require the operations outlined in the Form L until it is either cancelled or superseded. Arriving at a destination does not automatically void the Form L, as the train may still have operational obligations in regard to any subsequent movement. Similarly, a signal malfunction does not directly render the Form L void; rather, it may necessitate additional procedures to ensure safety and compliance with operational protocols. For these reasons, the condition of a new timetable coming into effect is the definitive answer to the question about when Form L's become void.