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DOT regulations: weight regulations for agriculture

Kristen Schulte, ISU Extension and Outreach Farm & Agribusiness Management Specialist

It is important to occasionally review Iowa Department of Transportation guidelines when hauling and moving agriculture implements and commodities. The following guidelines are taken from the Iowa Department of Transportation Truck Information Guide; this publication can be accessed from www.iowadot.gov/mvd/omve. Additional questions should be directed to the Office of Motor Vehicle Enforcement, 800-925-6469.

Registration Weight Tolerance

In Iowa, all trucks and combinations are allowed to operate in excess of their license registration weight by up to 5 percent, but are not allowed to exceed the maximum gross weight listed for total wheelbase. However, if transporting raw agricultural products* trucks or combinations are allowed to operate in excess of their license registration weight by up to 25 percent, but are not allowed to exceed the maximum gross weight listed for total wheelbase. A provision has been added for this exception to allow processed grain (i.e. cracked corn) as a raw product if the corn is transported to the processing facility and immediately returned to the farm. Additionally, a farm plated truck transporting distiller’s grain is also included under the 25 percent weight tolerance waiver. These two exemptions, 5 and 25 percent tolerance, apply only in the state of Iowa; the one exception is in Minnesota the 25 percent tolerance stands for Iowa farm plated vehicles.

Gross Registration Exception – Lightweight Combination for Farmers and Private Carries of Livestock or Ag Commodities

A motor truck in combination with a trailer or semitrailer, operated by a farmer or private carrier hauling horses, with county level registration or special farm registration may qualify for a gross registration weight exception. If the weight of the truck with transfer weight of the loaded trailer applied is 6 tons plus tolerance or less, and the total gross weight of the truck, trailer, and cargo is 12 tons plus tolerance or less, the truck may be registered for 6 tons or less and qualify. If the truck or total combination exceeds weight limits, the vehicle must be registered for the combined gross weight.

  • Registration Exception including 25% Tolerance
    • Truck must be properly registered for 6 tons or less
    • Truck and transfer weight must not exceed 15,000 pounds
    • Combined gross weight must not exceed 30,000 pounds

Implements of Husbandry and Truck Highway Weight Limits

All motor vehicles except for implements must comply with legal and posted limits on roadways and bridges; when on an un-posted roadway or bridge, weight must comply with corresponding registration weight based on number and position of axles. Implements are exempt from legal limits of roadways and bridges, but must comply with posted weight limits on bridges. Wheeled grain carts, tank wagons, and fenceline feeders must comply with the seasonal axle limit or a 96,000 pound gross maximum on a legal roadway. Seasonal axle weight limits for these implements are 24,000 pounds per axle from February 1 through May 31 and 28,000 from June 1 through January 31. On a legal limit bridge, these implements must comply with 20,000 pound per axle or 80,000 pound maximum weight limit; on a posted weight limit bridge weight it must comply with posted weight limit. Tracked grain carts, tank wagons, and fenceline feeders or self-propelled floatation applicators have additional requirements that can be identified in the Iowa DOT information guide.

Oversize Loads

Indivisible loads and vehicles that transport indivisible loads which exceed legal dimensions or weight, may be eligible to be moved by permit if the government agency with jurisdiction for the highways on the route of travel authorizes the movement and issues an oversize or overweight permit. Single trip and annual permits are available, with different limitations on their use. Exceptions are permitted for wide loads transporting implements during day light hours on non-interstate routes. These trailers must be marked with amber lights and wide load sign recognition. Contact the Iowa DOT for additional requirements before transporting oversize loads.  

*Raw agriculture products include commodities such as, but not limited to, ag lime, grain, hay, livestock, raw milk, straw, and fruit. Implements of husbandry include vehicles or equipment designed for reconstructed for agricultural purpose and used exclusively in an agricultural operation. It includes farm tractors, combines, grain carts, wagons, or fenceline feeders (referred to as implements).

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