I need to show a couple of miles (at least) of an elevated roadway for interacting with the site I am working on. Roads need to be projected to run underneath it, and the elevations differ so I need a realistic rendering. Is there some way, of better yet, some ONE, who can do that if I give them the coordinates and a .skp file to work from?
Use the layer tag to indicate stacking. Also consider using bridge=yes, or bridge relations. I’m not sure that there is any tag with significant renderer support for 3D mapping of stacking distances for outdoor features.