Thanks
@Bikerbrent and
@crashton . About five years ago I found an old searchlight signal still in service on CSX as an "Approach" signal with its APP marker. I like the evening light and how well the amber signal aspect shows in it.
Getting geeky, a signal equipped with an “APP” marker on CSX governs the
approach to the next signal, often at junctions. These are also known as "Distant" signals. With a yellow aspect, the engineman will slow the train to Medium speed (about 30 MPH) and be governed by the aspect of the next signal which guards a junction with another line. With a yellow aspect showing here, the train will be slowed and prepared to stop if the signal ahead guarding the junction is red. Norfolk Southern uses approach signals too, but instead of an APP marker, a time-honored "fishtail" shaped metal plate is attached to the signal mast in my area. These are a remnant symbol of old semaphore signals and an example appears in the second picture. [Both pictures taken with my D5100]