1. Storage of engineering (track) department tools and materials. Place this at section house or where section houses used to be, and in yards and terminals, reasonably convenient to trackside and where a truck can drive up to it, if possible.
2. Storage of signal department tools and materials. Place at signal district headquarters (e.g., every 50-100 miles on a single-track transcon railroad).
3. Storage for track speeders -- immediately adjacent to trackside with rails or timbers to roll the speeder out to the track, and planks between the rails to turn it and get it onto the track.
4. Backup power generators for signal systems (diesel or propane powered) -- at the base of the pole line and where a fuel truck can get to it, maybe every 100 miles or so. This is sometimes seen but by no means universal.
Small buildings are also used as switch crew shantys, for offices where local crews go to get paperwork for their days's work, for initial and final paperwork for road crews on low-density districts, etc. Basically any place where railroad employees regularly report to work, they need a building to store things and do paperwork, and get out of the weather while they do it.
Suggest you pick a railroad you like, one that's not too urbanized, and drive down it for 100 miles, stopping at every siding and switch, and shooting a few photographs at each location in all directions. Digital photos are free, so take a lot! You can usually do 99% of this without trespassing, either.
S. Hadid
I see alot of kits for track side sheds. I picked up a small (2" by 3.5" ) storage shed kit by North Eastern Scale Models. Where would these go, in yards, on stretches of mainline, by industry spurs? This is a neat little kit that I just might use as an abandon shack in the woods or something.
J.P.