Final answer:
A train operator observing an unattended white light should report the light to the authorities, as operating protocols usually require communication with the control center for safety instructions.
Step-by-step explanation:
When a train operator observes an unattended white light on the bench walk adjacent to their track in the subway, the most appropriate course of action is typically to report the light to the authorities. While the specific light signal meanings can vary by region or subway system, an unattended light could potentially indicate a hazard or require attention. Therefore, continuing to drive the train without acknowledging such a light or ignoring it could lead to unsafe conditions. It's imperative for the train operator to follow established protocols and communicate with the control center or relevant subway authority to convey the presence of the light and receive instructions on how to proceed. Unlike a scenario with a vehicle where rules might be more flexible in an emergency, such as with a pregnant woman in clear distress, train systems tend to have strict protocols to ensure the safety of passengers and staff.