The bridge is a girder and floorbeam system bridge, but its girders are rolled beams (not built-up plate girders). If you were to go underneath the bridge I presume you would see transverse floorbeams. Keep an eye out for more of these bridges, I find them very interesting and they seem to be spread out over a fairly large two state geographic region.
This is the second bridge of this kind I have now come across within a week or so. I am getting freaked out by this. What is going on? What kind of bridge is this??