The bridge deck is 12' wide, 16' long and 12" thick. I forget the weight capacity but it is rated the same as highway construction. Heavy equipment has already been over it and fully loaded concrete trucks are not a problem. The bridge provides access to my future house site. At about $13k it wasn't cheap buy I needed something that would not wash out and outlive me. In the grand scheme of things it wasn't too much more than a very well built/installed culvert with concrete wing walls.
The welding plates were installed by the company that made the pre-stressed decking and, since they are made for welding some sort of railing or brackets, should be OK.
I agree with the "woodsy look" and was thinking of using 6x6's for the uprights and railings (see drawing below). 1 concern I have is that the bridge is 12' wide. If I bolt the railings to the inside of the uprights (similar to Zep's 4th and 5th pictures) I will lose almost a foot of width. So it would make sense to attach the railings to the tops of vertical uprights which doesn't make for a great connection. I'm going to call a local welder/fabricator so get some ideas/quotes for brackets for the uprights and hardware to attach the railings.
