Updated 15/9/2018: Added Customizer support for the simpler cases, and published the OpenSCAD file for anyone interested.
Three variants of an N Scale double track footbridge. The model is of no particular prototype, although to a vaguely UK or Australian pattern. Intended to connect two 1" wide platforms with a 2" pit between them. The center span is 50mm, the full span 78mm, the overall width 102mm, the walkway width 12mm, with a headroom of 26mm.
Version B has been printed and tested on a FlashForge CreatorPro in ABS using default settings (0.18mm). The STL files have supports designed in, since the Slicer's auto-supports feature was inadequate. A raft is recommended but not essential.
The three variants can be cut, reassembled and stretched in your Slicer or STL Editor to suit different locations.
The design was done in OpenSCAD, originally as a generator of arbitrarily complex T Scale and Z Scale footbridges. This version has been cleaned up with a bit more detail added, although it is still a bit sparse for N.
Default (15%) (not fussy)