how would tessellation help with resource eating?
If you reach the same number of tris you can expect the same exact performance (or lack thereof).
Gravel can (Could in ue4) easily be faked with parallaxed textures.
Look into how to do carpets.
The rail / wood cross ties should be handled Ok anyway.
Look into the real thing, set up the same distances.
Each rail bar is a predetermined length.
Turns are also predetermined at a specific curve (mostly because if you exceed the curve tolerance you derail the train).
Ei: splines are a bad idea for a train rail… even if they are quicker than snapping parts together like a toy train.
If anything, you want a system that can generate a spline for the train to follow after the parts are snapped and built…