Variable mode operation is when signal operation changes between protected-only to protected-permissive mode, or between protected-permissive to permissive-only operation based on the time of day. It is possible with the 4-section FYA signal face when a study shows this type of operation to be beneficial. However, you must ensure that the controller is capable of switching between modes such that the flashing yellow arrow indication and the opposing through movement indication terminate together.

In other words, the controller should be capable of transitioning between modes without the flashing yellow arrow terminating while the opposing through movement stays green. Additionally, when switching between protected-permissive to permissive-only mode, ensure that the controller is capable of reassigning the left-turn detectors to call the associated through phases by time of day.