To move the train away from the signal source using light, which motion should be used?

• A. Wave light horizontally
• B. Swing light to circular motion
• C. Wave light in vertical direction
• D. Spin the light in place

Answer: (C)

In this signaling setup, the way the light moves communicates the action to take. A vertical sweep of the beam is the clearest cue for the train to move away from the source because it creates a distinct, directional pattern that stands out in a dim tunnel and aligns with the idea of retreat along the track. Horizontal motion, circular motion, or spinning in place can be ambiguous or convey different instructions, so they’re not used to indicate moving away. The vertical motion thus provides an unambiguous signal to back off from the signal source.