Locating Your Trail Bridge for Longevity
Appendix B— Example of Trail Bridge Design Folder
The following outline shows one way to set up a Trail Bridge design folder.
Section 1—General Information
- Executive Summary
- Aerial Photographs
- Quad Map
- Photographs
- National Environmental Policy Act Compliance
- Other Information
Section 2—Topographical Survey
- Topographical Survey Map
- Survey Notes
- Survey Photographs
- Other Survey Information
Section 3—Hydraulics and Hydrology
- Stream Classification
- Basin Area Map
- Infrared Photographs
- Regression Calculation for Flow
- Hydraulic Survey
- Hydraulic Analysis
- Hydraulic Recommendations
Section 4—Geotechnical Investigation/Substructure
- Soil Classification
- Soil Investigation
- Foundation Recommendations
- Description of Additional Geotechnical Investigations Required
Section 5—Structural Design/Superstructure
- Design Criteria: See FSH 7709.56b–Transportation Structures Handbook, Chapter 7–Structural Design, section 7.6–Trail Bridges
- Bridge Width: See section 7.61 and the Trail Bridge Design Criteria table
- Loads: See section 7.62
- Pedestrian
- Snow
- Wind
- Groomer
- Light vehicle
- Load Combination: See section 7.63
- Railings: See section 7.66 and the Trail Bridge Design Criteria table
- Length: See Hydraulics and Hydrology
- Sample Calculations for Bridge Superstructure
- Standard Plans To Be Utilized
- Special Project Specifications for Prefabricated Bridges
- Superstructure Recommendations
Section 6—Cost Estimate/Permits/Other Information
- Cost Estimate
- Permits
- Special Requirements—Timing, Helicopter, and So Forth
- Alternative Sites To Be Considered
- Additional Information
The following table is from FSH 7709.56b–Transportation Structures Handbook, Chapter 7– Structural Design, section 7.69–exhibit 01.
| TRAIL DESIGN USE | CLEAR WIDTH | LIVE LOAD | RAILING HEIGHT |
| Hiker/Pedestrian | 3 feet 5 | Pedestrian or snow load | 42 inches |
| Mountain Bike | 4 feet | Pedestrian or snow load | 54 inches |
| Pack and Saddle | 5 feet w/o railing 6 feet w/ railing |
Pedestrian or snow load | 54 inches |
| Cross Country Skiing | 6 feet | Pedestrian or snow load Groomer where applicable |
Site specific |
| Motorcycle | 42 inches | Pedestrian or snow load | 42 inches |
| Snowmobile | 6 feet | Pedestrian or snow load Groomer where applicable |
Site specific |
| All-Terrain Vehicle | 50 inches | Pedestrian or snow load | 42 inches |
Notes:
- Widths shown are recommended minimum clear widths between railings or curbs. Use design parameters developed for each particular trail, which may recommend narrower bridge width. If groomers are to be used on the trail, check the specific groomer machines for the necessary width.
- See section 7.62 for a description and minimum requirements of pedestrian live load.
- Railing height is the minimum if railing is required. Provide analysis to determine whether railings may be eliminated.
- For trail bridges that require access for light administrative vehicles, a minimum width of 8 feet is required. The design live load shall be AASHTO H-5 (10,000 pounds) vehicle loading.
- Except footlog bridges should not be less than 10 inches.
