What should the holding lights indicate during non-commission hours?

The correct answer indicates that during non-commission hours, holding lights should specifically signal connections between trains. This is important because holding lights serve a critical purpose in managing train movements and ensuring safety during periods when full operational control is not maintained.

When the system is not in commission, it is crucial to have clear indications for train operators regarding the status of connections. This helps prevent confusion and ensures that trains can safely wait for their turn to connect or proceed without conflicting with another train's path.

In this context, the other options do not accurately reflect the responsibility of the holding lights. Arbitrary use would undermine operational integrity, while stating that they indicate regular delays could lead to misinterpretations about the status of trains. Similarly, focusing on the operational status of track switches is not their primary function during non-commission hours, as holding lights are more about signaling train connections than the status of switches. Overall, the primary role of the holding lights is to ensure clarity in the train connection process when full oversight is not available.