I wanted a unique model to fit the following requirements:

• can stack as many elements as needed to build very high bridges
• track below can be parallel or perpendicular
• print without supports
• all wagons types fit under the bridge

I am quite happy with the result.

Print instructions:

• no supports
• i printed in PLA but i suppose any material would work too
• beware of bed adhesion: i strongly suggest that you activate a skirt in your slicer and go slow

Autodesk Fusion source attached in files section.