Can do also something more even if it is not a track mod thread.
I can share at least a "first step" method to smooth the tracks that works pretty well, assuming the starting mesh is acceptable.
I'll try to explain (difficult for me in English), moreover it's long time I have no time to work on Max so could be I'm not totally precise.
Credits have to be given to f.gek of Radiators (named Bessie from friends
) for all this instructions, gave me some time ago to help me to smooth my work.
1) select a sector of the track (set as an editable poly)
2) ALT+Q to switch in isolation mode
3) Vertex mode: select all vertex and WELD (the number of vertex will decrease)
4) Edge mode: REMOVE all edges that are not orthogonal (more or less) to
try to obtain a "regular" squared wireframe
5) REMOVE all free (not connected vertex) that should lay on some edges due to the edge you have removed on point 4)
6) select the first edge
7) Ring (you should see all parallel edges become red. If not check if
there is some isolated vertex near the point where the chain is
9) Repeat 7 and 8 to have at least 4 "lanes"
More or less DONE!
Then you have to check if there are holes between grass and track.
Eventually correct moving the vertex in an appropriate way.
You'll surprised to drive again your tracks, now smoothed in mesh discontinuity, but still with real "bumps" modeled.
Naturally the result may vary depending how good was the original mesh
If at this point there are still isolated "artificial" bumps, you have another possibility to use a sort of digital "scraper" locally.
Unfortunately I used it only one time (successfully by the way) and since it's a lot of time I dont work on tracks, I don't remember exactly how I proceeded.
But if needed I'll try to search my notes...
Hope it helps, let me know!