I went camping this past weekend and, while driving to/from our destination, we drove under a number of overpasses, bridges, etc. Some were clearly marked for height clearance and other were lacking of such signs. Does anyone here know why this is the case? Is there a law which states that anything over a certain amount does not require a clearance marking? Is this a federal thing or does it vary state by state?

 

I couldn't find the reference again, but I recently ran across something which talked about overpass heights. There's a Federal mandate for bridges on the interstate system. If they are lower than the required minimum it must be clearly stated. State roads are not mandated by the Feds and here's a web page which has state by state references for their local roads.

http://www.aitaonline.com/Info/Low%20Clearances.html

 

I *think* that anything under 16 feet is supposed to be marked, but I could be wrong.

chaikwa.