If you car to mess around a bit and are not squeamish, you could go with the Plastruct Truss bridge kit. They're not know for their kits being a pile of uncut shapes and some rudimentary instructions. That being said, they build a pretty nice and strong bridge with good representation of the real thing. I didn't use the bridge as a through truss since I had curves in the approaches, so I turned them upside down and used them as deck trusses. Since deck trusses are much narrower, I had enough material left over from two kits to produce and entire 3rd deck plate bridge and trussed pier supporting it. I did it "model airplane style" by pinning the pieces onto plans that I had redrawn in CorelDraw to 1:48. The Plastruct instructions are not in O'scale.
Instead of embossing rivets into the gusset plates I used rivet decals which worked pretty well. I would recommend it for those who don't want to mess with embossing.
Bridge shoes are from Kiel Line and the deck railings are from Bowser.
Track on bridges is special Ross bridge rail which has the guard rails already installed. Side walkways were constructed of balsa wood planks. I wouldn't do it this way again since it's quite fragile. I'd go with basswood (coffee stirrers?). As in some prototype practices, bridge shoes are only on one end.
They've been in operation now for 3 years are working great. I've had no trouble with them at all. Building this first Plastruct kit gave me the confidence to build other trussed structures including the material handling equipment on the distillery and Plastruct's refinery kit, which was soooo much harder than the bridges. I would not have wanted to tackle the refinery first.
