I think it was Mark Clark who said

Those in the US who may not have actually seen a speeding train, won't remember that the central headlamp on the front of steam engines moved back and forth sweeping it's light in an arc back and forth across the tracks.

I grew up in Minnesota, back in the steam train era, and lived in close proximity to a rail line.   I never, ever saw a train with a sweeping headlight.

Dave Oesterreich