Which of the following is NOT a signal type mentioned for governing movements?

The correct answer indicates that "Warning Signal" is not one of the standard signal types governing movements. In railroad operation, signals play a crucial role in ensuring safety and effective communication regarding train movements.

Clear Signals indicate that the track ahead is clear for the train to proceed at permitted speed. Approach Signals typically advise a train of conditions ahead that may require slowing down, indicating that the train should be prepared to stop at the next signal. Stop Signals instruct an engineer to halt the train completely, ensuring that they do not proceed when it is not safe to do so.

While "Warning Signal" can convey the idea of signaling caution, it is not categorized as a distinct type of railroad signal that governs movements. This distinction helps clarify the specific functions and meanings of established signal types, which are fundamental for the safe operation of trains on the railroad network.