Curiosity more than anything as to why the searchlight signals being installed in the N&S seem to be always on? Used to be when the track section was devoid of traffic the signals went out, now the signals can be on in any conditions regardless of traffic with Green showing to both directions or Red showing Both. I cross those tracks regularly while paralleling them for many miles in travelling my grain hauls. The same condition seems to be developing on the KCS and CSX routes in NE MO.
I'm not sure. NS signals in my area of the Carolinas are always on. When CSX installed PTC on the nearby SAL, the new signals were always lit, which was unusual. However, after a few months they reverted to their previous approach-lit status, i.e. dark until train time.
When I see clear signals for both directions I think the signals are Absolute Block Signals that display based only on track occupancy.
Signals can be configured to be either constant lit or approach lit. Why a carrier sets them one way or the other - Who Knows? Some time regime change will cause a change from one method to the other.
Have spoken with a few MOW personnel at the UP yard here, they saw these some time back suspicion is they leave them lit to not cycle the lamps which again is suspect in shortening lamp life. They do not hold to that line of thought and the UP signals cycle down after line clears.
Fun Fact: Specially designed signal lamps are available with two filaments inside if a railroad chooses to use them. Rather than make each lamp filament of equal brightness, the second filament alights when the primary filament fails and it's designed to burn more dimly. This feature gives train crews and signal maintainers an immediate visual notification that the lamp needs replacement, but without it failing in typical fashion by going completely dark and causing a slowdown on the line.
