There are three classes of silhouettes. First is a Single-Unit Truck, which comprises all straight trucks, cranes and other single-unit special mobile equipment regardless of the number of axles. Next, the Truck Tractor Semi-Trailer silhouette, which includes all truck tractor combinations regardless of the number of axles. Finally, the Single-Unit Truck with One Trailer, which includes all Maxi-Cube and Tandem Trailer combinations regardless of the number of axles. Be sure to watch carefully for all load limit signs and obey them.
What happens if you cannot break the load down to meet the weight requirements? A special permit may be obtained for oversize and/or overweight vehicles and loads. On interstate highways, your truck’s weight will be determined by external bridge length and by internal bridge (groups of consecutive axles). For example, the internal bridge can be either sets of tandem axles (four-axle bridge) or the axles of the tractor (three-axle bridge).
There is a formula to calculate your inner bridge but this only applies to your truck if the gross weight (overall weight of your truck and load) exceeds 73,271 pounds, and:
It has four axles and 47 feet or more wheelbase; or
It has five axles and 41 feet or more wheelbase; or
It has six axles and 33 feet or more wheelbase.
To measure your legal inner-bridge weight, measure the axle spacing between the groups of axles. Then find that length in the table provided in this blog (click here to view). One warning: you may be legal on external bridge weight, but not on internal bridge. Be sure to check those weights before using the Interstate highways.
Not following these guideless can lead to serious injury or possibly death. So please always consider your safety and everyone around you by checking your legal load size of your truck.
The Florida law regulates the size and weight of each truck and load. If you are in need of information on the fly, you can contact an office of the Florida Department of Transportation (DOT) or Office of Motor Carrier Compliance (OMCC).