Axle group weight and bridge formula
Maximum legal weight on a group of axles under the federal bridge formula, against the load you plan to carry.
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- Your own numbers, worked out as often as you like
- The full load plan you can print or save to My work
- 6 cited sources, linked, with the checks to make
- Every other tool for the same role, in the same plan
- A plain-words read of your result (a fuller AI read with the Bifrost AI add-on)
Included in these role plans
Example result · fictional numbers
What you get: load plan
Worked out by this tool from its default inputs. Its role plan lets you run your own numbers, print the sheet and save it.
79,000 lb on 5 axles, every group legal, 7 tie-downs
- Bridge formula result
- 80,000 lb
- Allowed on this group
- 80,000 lb (80,000 lb gross cap)
- Planned vs allowed
- 1,000 lb under
- Single axle limit
- 20,000 lb
- Tandem axle limit
- 34,000 lb
Axle weights
- Gross vehicle weight
- 79,000 lb of 80,000 lb on the Interstate
- Outer bridge (axles 1–5, 51 ft)
- 79,000 lb of 80,000 lb: 1,000 lb under
- Axle 1 (single)
- 12,000 lb of 20,000 lb; a steer axle is often limited lower by its tires
- Axles 2–3 (tandem)
- 34,000 lb of 34,000 lb: at the limit
- Axles 4–5 (tandem)
- 33,000 lb of 34,000 lb: 1,000 lb under
- Tightest group
- Axles 2–3: at the limit
Also on the sheet
- Every axle group (bridge formula) · 10 lines, starting with “Axles 2–3”
- Size and permits · 3 lines, starting with “Width”
- Tie-downs · 5 lines, starting with “Tie-downs needed”
The plain-words read of this example
At 79,000 lb on 5 axles, every axle and axle group is within the federal bridge formula. The tightest is axles 2–3, right at its limit, so a heavier load there needs weight moved. For the 42,000 lb cargo you need 7 tie-downs of this rating: chained direct, each counts at half its WLL, which is the step people miss, and a machine needs at least 4 anyway. The scale ticket and the state's own limits have the final say.
6 cited sources
- Federal Bridge Formula Weights (FHWA-HOP-19-028) (Federal Highway Administration, Office of Operations)
- 23 CFR 658.17, Weight (Electronic Code of Federal Regulations)
- 49 CFR 393.106, Aggregate working load limit (Electronic Code of Federal Regulations)
- 49 CFR 393.110, Minimum number of tiedowns (Electronic Code of Federal Regulations)
- 49 CFR 393.130, Heavy vehicles, equipment and machinery (Electronic Code of Federal Regulations)
- Cargo securement rules (Federal Motor Carrier Safety Administration)
Plus 6 step-by-step checks, a print layout and a link that reopens it with your numbers.