Okay, let me demonstrate my ignorance and take a shot at this based on no real knowledge but some (maybe)logic, railroad experience (which is not generally logical), and empirical evidence (a few pix). The subject intrigues me because in a 41 year railroad career I never ran across any "plan" for why what kind of switch stand should go where....although I'm sure there was one.
Browsing the pix suggests that on the ng. the high stands were pretty much "standard" in both yards and mainlines. Could find no low level stands on any mainline locations. But that is hardly definitive.
The various types of low stands appear to be used primarily in yards where there would not be enough clearance for a man hanging on the side of a car while switching, other confined areas, or where two switchstands were close and different heights improved visibility (my first picture above).
A subset of the low stands are the kind that are thrown by a weighted lever that "flops over" (my second picture above). I think the flop overs were easlier to throw than the regular low level stands, and used in situations needing a low profile AND getting a lot of use. They also provided even more clearance in really close confines.
Most of the high level stands seem to have the circular targets....I have absolutely no idea what the difference would be between the diamond shape targets and the circular ones. I found examples of both in the Alamosa yard, although most seem to be circular.
I would also guess that Frank's suggestion that what was first out on the closest supply "pile" also played a role, as well as when the switchstand was last replaced. I can remember in the early 60's a harpstand still in use on the wye at Elk Park.
All that being said, this is probably covered in detail in some maintenance of way handbook hidden away somewhere. The DRGW did have a lot of written track standards, but I don't have copies of them.
My guess is PRSL or Jerry Day or Oz or somebody more knowledgeable can add to/correct the above.
JBW
