In another thread about dual scale mapping I mentioned ICC Field Notes. These are the track ROW survey used during the VAL Map development.
Here is an example from a project I did a couple years back. I was trying to locate a parcel from an abandoned RR for a client to buy. It was a station parcel and the tracks have been gone for over 20 years. All I had was some remaining fences, culverts and some of the foundations still remained from the station. The deeds weren't all that good and the station parcel deed had a big ole error in it.
Anyway the field notes are sort of unique, dual scale, station offset and the curves are shown as a straight dashed line. If you haven't done much work on RR.s (like me) you may not have seen these before. Charlie Tucker helped me get these. You can get them and they may be helpful.
It's a several page pdf, the maps are at the end.
Looks like they spelled "gauge" differently in 1918. 😉