Using some altBricks architectural elements for a couple train projects. The first is a truss load for a flatbed car and a modular bridge design. We also have the LDraw .dat files for the 2x2x2 and 2x3x2 girder elements to use with MLCAD or other LDraw compatible CAD tools. Thanks for help from Max Martin Richter on these files!
Download the 2x2x2 (EP_1x2_Truss.dat) girder element.
Download the 2x3x2 (EP_1x3_Truss.dat) girder element.
Here is a flatbed car with a super simple "truss load" model using the 2x2x2 element. Although its simple visually is compelling.
Here's a modular train (or street) bridge using both 2x2x2 and 2x3x2 girder elements. This is a photo of two segments end to end. Here is the Truss Bridge Instructions in PDF format.