What is the effect of Form D Line 4 on signal indications within the limits of an out-of-service track?

Form D Line 4, when invoked, communicates that the specified track is out of service and indicates conditions for signal indications within that area. The correct understanding here is that the absolute block signal systems, control signal systems, dispatcher control systems, and interlocking rules do not apply within the limits of an out-of-service track. This means that signals will not provide the typical indications associated with those systems, effectively rendering them non-operational in the context of track safety.

While it may seem logical to think that signals might indicate caution or stop due to the abnormal conditions of an out-of-service track, Form D Line 4 specifically eliminates the application of those signaling rules, creating a distinct scenario that mandates a different protocol. It’s essential for safety that crews are aware of this state to avoid miscommunication regarding signal indications, thereby protecting both personnel and equipment.