Final answer:
Two lamps are used in the train operator's indication light fixture in order to enhance the illusion of a single light source and create a more realistic scene.
Step-by-step explanation:
The most probable reason for using two lamps in the train operator's indication light fixture is to enhance the illusion of a single light source. By using multiple lamps, the lighting designer can create a more realistic scene by providing additional primary and secondary lighting. This allows the audience to focus on the actors and creates a more immersive experience.