Common controls for a gyralight include a toggle switch. Center is off (motor does not run), spring return back to off is "inch", and the other was is "run". By using the inch position, you can get the gyralight aligned with the track, making it a substitute headlight. SP even had temporary gyralights that attached to the handrails and ran off the mu plug.

I did see a few SP and KCS trains that had ditch lights and working gyralights - no mistaking them! Alaska's GP49's had headlights, gyralights and ditchlights that flash when the bell is rung.

I've heard complaints that gyralights could hypnotize the crew. I never had an issue with that, but 95% of my running with them was in daylight. I know the flashing ditchlights at night are annoying if you are the engineer.

I think the better question is where to mount the gyralights - high between the number boards or low in a short nose unit? Fog and snow make any high mounted light reflect back into the cab. I think Amtrak's F59's have a special "fog" position - dimmed headlight but full ditchlights. (Amtrak tried to order them with ditchlights also - EMD gave them an outrageous price to modify the plastic noses.)