Modern suspension bridges do have a traffic limit, but designs are often more determined by seismic and wind loading concerns. The stress on bridge members as a shorter truck rolls across is much more than that caused by a long vehicle, even though both trucks may have the same total weight and individual axle weights. Bridge formulae are used for truck size and weight regulations in the U.S., Canada (Ontario), Mexico, Europe, South Africa, Australia, and New Zealand. The additional weight allowed cannot exceed 550 pounds or the weight certified, whichever is less. Okay, most of the time the bridge breaks no matter what. You can assume loads (weight on the bridge) and geometry (shape and size of the bridge and its components), and calculate stresses from there to see if your structure will fail or not.  Although this means that any two axles must comply with the formula, experience has shown that axles 1 through 3, 1 through 5, and 2 through 5 are critical and must be checked. We know a lot about trucks and we use this knowledge to build intelligent software for people who sell, upfit and use trucks. per sq. We then take that weight, combine it with all other possible loads (winds, seismic, self weight etc.) In Florida, any vehicle that exceeds the limits by more than 6,000 pounds (2,700 kg) is required to be unloaded until the vehicle is in compliance. L = spacing in feet between the outer axles of any two or more consecutive axles. This difference in weight distribution would allow a person to cross an area of ice while crawling that might otherwise collapse under their body weight while standing up. per square foot. These weigh stations are run by state DOTs, and CMV weight and size enforcement is overseen by the FHWA. If these combinations are found to be satisfactory, then all of the other axle groups on this type of vehicle will usually be satisfactory. Some states, such as Connecticut, issue fines on a percentage basis (e.g. , Formula for estimating bridge weight limits, American Association of State Highway and Transportation Officials, Federal-Aid Highway Act Amendments of 1974, Federal Motor Carrier Safety Administration, Surface Transportation and Uniform Relocation Assistance Act, "Chapter 2: Truck Size and Weight Limits", "Federal Bridge Formula: How It Influences Vehicle Dynamic Behavior", "2006 Montana Commercial Vehicle Size and Weight and Safety Trucker's Handbook", "Federal Size Regulations for Commercial Motor Vehicles", "Highway Accident Report: Collapse of I-35W Highway Bridge", "New Research on Pavement Damage Factors", "Bridge Load Rating, Permitting and Posting", "Chapter 191: Authorization to Use Bridges Due to Condition of Bridge", Pennsylvania Department of Transportation, "Fault Tree Analysis of Schoharie Creek Bridge Collapse", "Truck Collapses Bridge in Grays Harbor County", "Commercial Vehicle Size and Weight Program", "Criminal Penalties for Overweight Trucks", "316.545 Weight and Load Unlawful; Special Fuel and Motor Fuel Tax Enforcement; Inspection; Penalty; Review", "23 USC 127: Vehicle weight limitations-Interstate System", "Questions and Answers about Vehicle Size and Weight", Owner–Operator Independent Drivers Association, National Motor Freight Traffic Association, Glossary of the American trucking industry, https://en.wikipedia.org/w/index.php?title=Federal_Bridge_Gross_Weight_Formula&oldid=969475623, United States Department of Transportation, Creative Commons Attribution-ShareAlike License.