Don't forget it has a nice "dip" as you go under... so the longer you are, the lower the trestle is... I've yet to see a standard semi get caught on it though.
Back before they worked on it, the overpass at I-24 Exit 152 Kimball/South Pittsburg (TN) would scrape the air conditioners off of tall RVs on a regular basis. They had overhead warning chains on the turn lane but it was impossible to change route by that time. Bad thing was the road dipped so much and so sharply that even the standard semis would barely clear it. Too long and they hit (mostly those huge fifth wheels). It's strange to watch someone scrape their roof top AC units off their RV. Apparently it's difficult to tell when it's a fifth wheel trailer. Oddly enough, Shaw carpet mills had a factory in S. Pittsburg, so lots of semis drove there. I once sat and watched a fiver scrape 3 AC units off... guess they didn't want them anymore.