3.3 Maximum Load with Permit

It is often necessary to transport loads that result in the maximum vehicle weight exceeding 80,000 lb. This is evidenced from the weight distribution shown in Figure 3.1. These data are from one highway measurement location in Florida for a full year. As can be seen in this figure, there is a significant percentage of trucks with weights greater than 80,000 lb (i.e., \(8 \times 10^4\))

Figure 3.1: Truck Weight Distribution

Source: Gurley and Washburn (2005)

In these cases, a special permit must be obtained from the applicable state transportation agency(ies) (e.g., Florida DOT). It should be noted this process also applies to vehicles that exceed the base dimensional limits (e.g., a load carried on a flatbed that will be higher than bottom of most roadway overpasses).

If a permit is granted by the transportation agency, it will usually include certain restrictions. For example, the truck may be restricted to travel only during certain times of day (to minimize conflicts during heavier traffic periods) and/or may not travel on certain roadways. In the case of the latter, there may be routes with bridges that cannot handle the weight load. The truck may also have to avoid higher-speed roadways, such as an interstate, because the weight prevents the vehicle from attaining higher speeds. In some cases, it may be necessary for the DOT to map out a specific route from the origin and destination.

In some situations, one or more pilot vehicles (sometimes also referred to as escort vehicles) may also be required to travel with the tractor-trailer. See https://www.truckinfo.net/guide/what-is-a-pilot-car for more information on pilot vehicles.

Additional information about the permitting process for overweight and/or oversize trucks can be found at the following sources:

References

Gurley, Kurtis, and Scott S. Washburn. 2005. Probabilistic Assessment of Bridge Loading Concurrent with Permit Vehicles. Tallahassee, Florida: Department of Transportation Research Office, State of Florida.