The federal interstates are supposed to have 16' (4.9m) clearance under bridges. However in older parts of the country (mostly the Northeast) there are many bri

The federal interstates are supposed to have 16' (4.9m) clearance under bridges. However in older parts of the country (mostly the Northeast) there are many bridges that don't have that clearance and have been grandfathered in. And of course, Texas has bigger clearances, because Texas. https://en.wikipedia.org/wiki/Interstate_Highway_standards https://en.wikipedia.org/wiki/Interstate_Highway_standards edit Looks like Texas may have consulted with the Army's Transportation Engineering Agency for design input, as it's mentioned in their design standard manual http://onlinemanuals.txdot.gov/txdotmanuals/rdw/freeways.htm#CHDGBIHC http://onlinemanuals.txdot.gov/txdotmanuals/rdw/freeways.htm...