This is a set of pieces to build your own modular bridge or overpass. Ideal for war games or your kids' Matchbox cars. Pier height should be good for 3 stacked layers of 1-1/2" foam insulation if that's your terrain construction material of choice.
Works well with my Jersey Barriers: http://www.thingiverse.com/thing:55070
April 10, 2013: All old files have been updated and replaced. New files for complete set added.
April 27, 2013: Slight changes to short beam & road end for better end-piece-only short bridge option. Added 3-column pier support as an alternative option. Removed "Work in progress" tag, but I'll probably keep adding new bits from time to time.
Print two long beams for each center road section. Print two short beams and one abutment for each end section. Print one pier for each joint between road sections. For a very short bridge, you could use two end sections, two long beams, and two abutments.
The road section is drawn at 180mm x 180mm. If your print bed is smaller, scale all parts accordingly. 67% should still work well for Matchbox cars, Hot Wheels, etc. while still using two stacked layers of foam insulation to carve terrain.