The bridge was retrofitted a few years ago and raised 8 inches. Doesn't sound like a lot, but it eliminated many of the truck shear-offs. Still gets a few, though. Took the air conditioning units off the top of a long camper a couple of weeks ago.
Here's the great website, 11foot8.com
http://11foot8.com/
Note that it's no longer the bridge that decapitates the trucks/campers. It's a steel beam in front of the bridge, so that the bridge doesn't suffer damage from the stupid drivers.
The bridge itself cannot be raised any higher. Trains cannot deal with steep grades (anything much over 1% or so) and so significantly raising the bridge would require long rebuild. In this case, I believe it would affect the downtown at-grade crossings, plus Buchannan on the other side. The 8 inches were obtained by changing the bridge beams to a stronger/shorter steel.
The Campus Drive bridge (Main St. on top) was replaced a couple of years earlier, so it's no longer quite as tight either.