Which interlocking signals are used in Harrison Yard for permissive signaling?

The interlocking signals used in Harrison Yard for permissive signaling are identified as 140X and 180X. This type of signaling allows train movements to proceed under certain conditions, often to facilitate safety and efficiency in yard operations.

The 140X signal generally permits trains to move while ensuring that they are adequately prepared to stop at any potential obstructions ahead. This signal is particularly important in areas where multiple tracks converge and train movements need to be carefully managed.

The 180X signal serves a similar purpose, enhancing the capacity for trains to move through the yard while providing critical information about the status of the tracks, switches, and upcoming traffic. By using these two signals in conjunction, the Harrison Yard manages train movements effectively, helping to prevent conflicts and maintain safe operations.

The other options consist of signals that may not serve the same purpose or may not be utilized in Harrison Yard for permissive signaling specifically. Understanding the function and application of these particular interlocking signals is crucial for maintaining operational safety in complex rail environments like the Harrison Yard.