Truss Bridges

Below: Pony Truss Footbridge, Newton:

 A pony truss is a truss bridge which allows traffic through the truss, but the top of the bridge is not joined together with cross braces.

https://mass.pbslearningmedia.org/resource/lsps07.sci.phys.maf.dstruss/design-squad-truss-bridge/

https://mass.pbslearningmedia.org/resource/arct14.sci.dstruss/what-is-a-truss/

David Macaulay: Train Truss Animation
https://mass.pbslearningmedia.org/resource/phy03.sci.phys.mfw.bbtrussanim/train-truss-animation/

https://garrettsbridges.com/category/popsicle-bridges/