I got assigned to work the Agent/Operator’s position at Salem, IL off and on in 1966 & 67. The station is located on the apex of a slight curve. Looking East on a clear night you could see the headlight of Westbound trains BEFORE they activated the ‘bell’ circuit passing the West Switch of the siding at Iuka - 6 miles to the East. You could also see the headlight of Eastbound trains before they activated the ‘bell’ circuit by going over the railroad crossing at grade with the Illinois Central at Odin, IL six miles West of Salem.
With regard to the Mars lights, recall riding the ACL’s East Coast Champion and South of Richmond my father opened one of the Dutch doors and we watched for several minutes as the ACL lead engines’ Mars light painted the Virginia countryside.
Headlights in the USA are more about the train BEING SEEN than it is for its operators to see.
I remember seeing a picture of a Northern with what I now know was a Mars light, wondering why there would be a traffic light on the front of the locomotive. Bear in mind I was in third grade when I first saw that picture.
It seems in general the headlight was in front of the stack until somewhere around WW1 era when it often was placed on the smokebox front. Perhaps something to do with change from dimmer oil burning lamp to electric lights?
Milwaukee Road 261’s red light is more like an emergency light than a usual Mars or Gyralite. It normally isn’t used when the train is running.