It is complicated as it is, so I don't think I'll add the wheel ruts, although it would 'only' be some extra warped thin lines used as masks. I did make the 'rut areas' of the road lower, as if they were worn by loads of wagons, and the finer ruts subsequently eroded a bit again. I think the rut area gravel needs to be a little finer, that's something easy to implement.
I do the objects in Lightwave, blabla. After a lot of trials and frustration I'm getting the hang of it (a bit).