Why are two lamps used in the train operator's indication light fixture?

The use of two lamps in the train operator's indication light fixture serves primarily as a method of redundancy. If one lamp were to fail, the other would still function, ensuring that essential indications remain visible to the train operator. This redundancy is critical for safety, as it helps prevent situations where a burned-out lamp might mislead the operator regarding the operational status of the train or track conditions. By having two lamps, the system ensures continued reliable communication of important information, thereby improving overall operational safety and efficiency.

While other options suggest alternative benefits such as illuminating different sections of the track, increasing brightness, or indicating different statuses, these do not capture the primary safety-focused intention behind using two lamps.