Bridge Formula

The Bridge Formula is a federal axle-weight calculation in U.S. freight and trucking that limits the allowable weight on a group of two or more consecutive axles based on the number of axles and the distance between the outermost axles. It protects highway bridges from concentrated stress and helps determine legal load placement on trailers.

In manufacturing supply chains, the Bridge Formula is a daily constraint when dispatching dense freight—coil steel, castings, resin, bagged minerals, or machine tooling—on Interstate routes. Load planners must match pallet and skid layout to axle-group weight because a trailer can be under the 80,000-pound gross limit yet overweight on one tandem or tridem group. This creates a control point between WMS/TMS and the loading dock. The warehouse may know each pallet’s tare and net weight, but legal release depends on how that weight is distributed across the trailer’s axles. A dense stack placed too far forward or rearward can overload steer or tandem axles, forcing scale-house rejection, dock rework, and missed carrier appointments. Therefore, dispatchers must consider trailer geometry, axle spread, and load placement—not just capacity—when planning shipments of dense industrial goods.