When may on-track equipment make trailing point movements through variable switches?

The correct answer is that on-track equipment may make trailing point movements through variable switches only if the switch is lined for such movement. This safety rule is vital because it ensures that the switch is correctly set to allow the equipment to pass safely. If the switch is not lined appropriately, it could potentially lead to derailments or accidents, putting both the equipment and personnel at risk. Ensuring that the switch is lined for the intended movement is a key aspect of maintaining operational safety and integrity on the railway.

Other options do not prioritize safety and proper procedure. The operator indicating is not sufficient if the switch is not correctly lined for the movement, and regular maintenance hours do not override the necessity of proper switch alignment for safe passage. The track being clear of traffic is also not a substitute for having the switch properly set up for the intended movement through the variable switch.