The great thing about corridor models is that you can build them before you have a lot of information. Let’s say you don’t have your lane width nailed down yet. No big deal, just adjust it later. The problem comes when you have a lot of assemblies- especially when working around intersections, etc.
You’ve probably noticed that with each release of Civil 3D, you can do more and more with the AutoCAD Properties dialog. Instead of going into the Assembly or Subassembly properties for each and every one of these lanes, I can select them all and under the Advanced area change their width. They will all update, then I just quickly rebuild my corridors.