Grand Trunk Western Model Railroad Bridge

This is a typical example of a project encompassing a dozen or so bridges built by the GTWRR in 1930 and 1931 to take the tracks northwest from Detroit.
For photos see -
https://historicbridges.org/bridges/browser/?bridgebrowser=michigan/oakland13mile/

The OpenSCAD model is parametric, you can select 2, 3, or 4 track widths for the bridge width, the bridge length is adjustable over a reasonable range, and the skew of the bridge versus the road below can also be adjusted.  Use the Customizer window to make adjustments.

The model includes all the parts needed, but most have to be printed twice for a complete bridge.  The bridges included the date of construction on one of the columns at the base of the retaining wall.

The main abutment and the bridge deck itself can easily be built from wood.  This is probably the preferred method since it would save a lot of print time and filament. 

The parapet corner columns need to be printed with grid supports from build plate.

Update: I corrected the arch spacing for the piers, and set up the 3mf with suggested print settings, mostly use variable layer height, ironing, 40% infill, and adaptive cubic infill for the piers ( since they are mostly shells and the top layer is not visible) and gyroid for the remainder of the parts (to make them more robust).