Signaling question

[miata54]

While running Feather River Canyon towards Keddie, I notice several types of signals, some single headers, some double headers. Some placed to the right side of the track, some to the left. Saw some single headers to my direction of travel to both the left and right. I understand that you will see signals at switch points and signals all by themselves along the way, but what determines the physical location, left or right of the track, when there is ample room on each side, for placement?

[kris120]

On single-track lines, the placement of signals usually does not matter. Right is preferred, of course. Often, signals of the opposite direction are mounted on the same poles, which saves money. Then the signals are often placed on the side that is easier to reach for maintenance or at blind spots so that the signal is visible from further away.
Signals with one head are usually placed as exit signals, in front of switches multi-headed signals are mandatory. Multiple heads only make it possible to display several lights at the same time and the individual lights are easily recognizable individually from a greater distance. But there are also heads which can show several lights at the same time. In the concrete case, of course, the rules of the railroad company are always decisive.