Where are permissive signals located?

Permissive signals are specific types of signals used primarily to allow the movement of trains under certain conditions, often when the main signals are not displaying a clear aspect. They are strategically placed to ensure safe operations in locations where train movements need to be controlled or guided, while still allowing for flexibility in the schedule.

In the context of the PATH system, permissive signals are located in Harrison Yard. This location is critical as it allows for the safe and efficient management of train movements within the yard. Harrison Yard serves as a hub for train operations, maintenance, and storage, where such signals are essential for guiding trains around conflicting movements, ensuring safety while reducing delays.

The other locations mentioned—Tunnel A and Tunnel B—do not have permissive signals because their operational requirements and safety protocols differ from those in a yard setting. Typically, tunnels may rely more on mainline signals that define the essential operating conditions for trains traveling through confined spaces, making the strategic placement of permissive signals in the yard more pertinent. Therefore, the correct answer points to Harrison Yard being the sole location for permissive signals in this context.