Race Track -- DupliFrames

28.  Fix Normals (if needed)
  •  3D View menu >> Mesh >> Normals >> Recalculate Inside
Note:
  • You can select each mesh face with Normals facing down and flip them individually
     
  • For this tutorial, I am selecting all of the faces and using Recalculate Inside to fix the Normals
29.  Track outline
  • While this tutorial uses the simplest possible shape for the track, the same steps are used for any shape.  The outline of a tunnel.  The outline of a bridge.  The outline of a road with stone walls.  Etc.
Download Finished blend: