Ok, so build the road in another 3d modeling program, import a terrain into that program, use a drape function like cloth to lay the road on the terrain, then export the road into vue and paint the eco system around the road?
That is something I can do in 3dmax. I just need to make sure the road is thick enough to protude through the terrain when back in vue and the cloth material in 3dmax is thick enough not to pick up the minor bumps in the terrain.