Is there a way of merging together two flat meshes A & B so that all vertices/edges/faces of B become part of A. Mesh B is a simple overlay (road) on top of mesh A (terrain). For performance reasons, this needs to end up as a single low poly mesh with a single material texture. Therefore road polygons and other parts of terrain need to have clear boundaries within the mesh to correctly unwrap.
Now I have the terrain and roads as two separate meshes. Merging these as two objects (Ctrl+J) will glue the two together but leave multiple overlapping faces fighting with each over at z. I believe I can also use Shrinkwrap to put one on top another with some offset but this is not what I'm looking for. Is there a way to simply weld one mesh with the other so that the whole structure becomes a single mesh with no duplicates or overlaying/double faces? Without manually tracing the pretty large roads mesh?
Thanks for any hints