Are there any through girder bridges extant? I'm not talking about pony girder bridges: these are very common. I'm looking for bridges with bracing on top of the bridge superstructure that connects the girders on each side of the bridge so that traffic goes "through" the bridge. There are no overhead braces on a pony bridge.
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fupload.wikimedia.org%2Fwikipedia%2Fcommons%2Fthumb%2F7%2F7c%2FBritannia_Bridge_wrought_iron_section.jpg%2F640px-Britannia_Bridge_wrought_iron_section.jpg&hash=7592f4fdafe888b7617dc224e1a558d65dc4b0a7)
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Steve Gum appears to be correct.
http://en.wikipedia.org/wiki/Tubular_bridge
You can also crawl through one of these: http://en.wikipedia.org/wiki/Box_girder_bridge
I believe the pedestrian bridge that once crossed NJ 120 in East Rutherford between the former Brendan Byrne Arena and the former Giants Stadium, did qualify at the time. I cannot remember the exact design, though many foot bridges now are being built inside the box that is the entire girder system for aesthetic purposes.
Roadman: Just stop believing. That flimsy motherfucker had nothing going for it. It swayed when 4-year-old me kicked the side.