Some might remember the BQE right off the Verrazano bridge once it it turns to an upper and lower roadway all the signs say 12 6 only. Every other 13 6 coming into the boroughs fit under every bridge. I think I heard a reason once for that but can't remember it.I ran Binghamton NY years back. Most bridges marked 11' 9". You can get under everyone of them with a 12' 6". They were marked 1 foot lower for some reason.