Neat Bridge

That's a cool bridge. I'm no bridge expert, but I think that would be considered a covered Howe truss, but not a "pony" truss. A pony (or low) truss (like the one on the WW&F) has side trusses that are not as tall as the height of the intended traffic. This is what precludes a roof (or bracing) over the whole structure.

The Great Northern Railroad bridge in the photo has braces across the top, so it would not be a pony truss; but it does lack a full roof. The cross bracing across the top of the GN bridge supersedes the need for the outrigger braces on the WW&F/B&M bridge. Regardless, the GN bridge is certainly another rare survivor of similar design.

See:
http://lostbridges.org/details.aspx?id=WA/47-38-01&loc=n
http://www.dalejtravis.com/bridge/washingt/htm/4703801.htm

Ed Lecuyer
Trainmaster, WW&F Railway Museum
Help the WW&F Build Locomotive #11: [build11.wwfry.org]