One of the basic tenets of freewayblogging is that everything surrounding the freeway is fair game, not just overpasses. Anything you can clip, nail, tape or strap a sign to is a potential posting spot: fences, trees, bridges, poles... anything. So long as there's a a clear line of sight between the text and the traffic, people are going to read it. Lots of them.
USA - 990
FB - 794