What is the function of a "restricted signal" during train operations?

The function of a "restricted signal" during train operations is to indicate the need for reduced speed. This is crucial for maintaining the safety and control of train movements. When a restricted signal is displayed, it communicates to the train crew that the train must proceed at a lower speed than normal operational limits. This regulation may be necessary in situations involving potential hazards such as track work, a degraded track condition, or other circumstances that require heightened caution.

Operating at a reduced speed allows the crew to react more effectively to any unforeseen obstacles or signals encountered during the journey. It is vital for ensuring the safety of the train, its crew, and other personnel on or near the tracks. Unlike the other options, which suggest bypassing established protocols or giving permission for uncontrolled actions, the restricted signal specifically emphasizes caution and careful adherence to safety guidelines during operations.