what it is: 11' 8''
where i found it: reader jpw
So here is a site created by a guy who is fascinated by the slightly-too-low railroad crossing outside of his office window that trucks sometimes run into. He's set up a camera and recorded hundreds of overhead impact incidents over the past few years and seems to have really thought about it a lot (check out the FAQ section). He also sells t-shirts. His name is Jurgen.