After finding exact height....ours is 12 ft 9 inches for 5 er so use 13 bridge clearance for passing under.....that being said....we use the all stays app and have hts programed in there for warning.....along with trucker atlas that shows truck routes....so have good idea where is safe....also the posted height by sign is the low point of the structure.....so lots of time can pass under by changing lanes or point away from low spot....if get caught HP can give you correct info for passage if possible with escort.....in fact we are at a spot where there are several trees that have low clearance posted...so is not restricted to bridges and tunnels.....and if have to measure for myself have a bream buster pole that collapses to verify heights....good luck hope you don t get caught in one of those 8 footers off the main route ( hence truck atlas) keeps that from happening.....