Instantly verify truck axle weights against FHWA bridge limits
Fleet dispatchers and heavy-haul truck operators prevent costly weigh station violations with our Federal Bridge Formula axle check calculator. By entering axle spacing and group counts, you can instantly run the complex equation (W=500[(LN)/(N-1)+12N+36]). The tool verifies inner bridge groups against standard single (20k), tandem (34k), and gross weight (80k) caps, ensuring optimal load distribution across interstate highway bridges.
The formula is designed to protect highway bridges from catastrophic damage. It ensures that heavier vehicles are longer and have more axles, spreading the intense weight load over a greater distance rather than concentrating it in one spot.
On the interstate system, the standard maximum weight for a tandem axle group (two consecutive axles spaced more than 40 inches but not more than 96 inches apart) is 34,000 pounds.
In the equation W=500[(LN)/(N-1)+12N+36], "L" stands for the length, measured in feet, between the centers of the extreme axles of the specific group being evaluated.
No, while 80,000 lbs is the maximum federal gross weight limit, shorter vehicles with fewer axles may be restricted to a much lower gross weight by the Bridge Formula to prevent concentrated stress on bridge structures.