Atlas O releases and ships their single track Prass Truss Bridge kit and a kit to expand it to double track.

Here's a shot of one of the four Atlas O bridges we have on our layout:

These feature Atlas O Track, but you can use the various connectors Atlas makes which we have in stock, to use this bridge with the other track systems. 

Atlas is offering the single track bridge, and then a separate kit to convert the single track bridge to a double track bridge. They are not making the double track version as a complete kit at this time. 

These are in stock and ready to ship.

• Atlas O 6920 - Single Track Pratt Truss Bridge Kit - $204.95
• Atlas O 6922 - Bridge Add-On Kit - $94.95