Bridge Formula
Logistics Term
Bridge Formula Definition
The Bridge Formula, also known as the Federal Bridge Gross Weight Formula, is a calculation used to prevent bridge damage from heavy trucks. It limits the weight-to-length ratio of a vehicle and calculates the maximum allowable weight based on axles.
In lamens terms, the Bridge Formula distributes weight more evenly over large road areas to prevent damage.
Formula: W = 500 [(LN / N-1) + 12N + 36]
W: Maximum weight in pounds that any set of axles on a vehicle may carry on the road.
L: Distance in feet between the outer axles of any group of two or more consecutive axles.
N: Number of axles in a group.
Maximum weight limit: 80,000 lbs
Bridge Formula Exceptions and Compliance
Oversized and overweight loads often exceed the bridge formula specifications. State and local entities require transport permits to ensure safety. When a load exceeds the allowance of results from the bridge formula table, and permits are obtained, specific regulations, such as strict times and routes, are implemented.
To meet compliance requirements, drivers must stop at designated weigh stations. If a truck is over the limit, the DOT may require offloading before the driver is permitted to leave, or the office may implement a fine.
