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Standard Trail Plans and Specifications - US Forest Service
Sustainable Trail Bridge Design - US Forest Service
What are good designs for volunteer-buildable trail bridges?
Build Your Own Trail Bridge - AQHA
Sustainable Trail Bridge Design - American Trails
Trail Bridges - Rails to Trails Conservancy
Sustainable Trail Bridge Design - Trail Skills
(PDF) Sustainable Trail Bridge Design - ResearchGate
Trail Bridge Catalog - US Forest Service