Minnesota: State Patrol, St. Paul, MN. 651-297-3935.

169.81, Subd. 5. Manner of Loading.

No vehicle shall be driven or moved on any highway unless such vehicle is so constructed, loaded, or the load securely covered as to prevent any of its load from dropping, sifting, leaking, blowing, or otherwise escaping therefrom, except that sand may be dropped for the purpose of securing traction, or water or other substances may be sprinkled on a roadway in cleaning or maintaining such roadway. This subdivision shall not apply to motor vehicles operated by a farmer or the farmer's agent when transporting produce such as small grains, shelled corn, soybeans, or other farm produce of a size and density not likely to cause injury to persons or damage to property on escaping in small amounts from a vehicle. Violation of this subdivision by a vehicle that is carrying farm produce and that is not exempted by the preceding sentence is a petty misdemeanor.

Subd. 5b. Securing load; exceptions.

  1. The driver of a vehicle transporting sand, gravel, aggregate, dirt, lime rock, silica, or similar material shall ensure that the cargo compartment of the vehicle is securely covered if:
    1. The vertical distance from the top of an exterior wall of the cargo compartment to the load, when measured downward along the inside surface of the wall, is less than six inches; or
    2. The horizontal distance from the top of an exterior wall of the cargo compartment to the load is less than two feet. 
  2. The driver shall not operate a vehicle to transport sand, gravel, aggregate, dirt, lime rock, silica, or similar material in or on any part of the vehicle other than in the cargo container. The driver shall clean the vehicle of loose sand, gravel, aggregate, dirt, lime rock, silica, or similar material before the vehicle is moved on a road, street, or highway following loading or unloading.
  3. A driver of a vehicle used to transport garbage, rubbish, trash, debris, or similar material is not required to cover the transported material as long as
    1. the vehicle is being operated at a speed less than 30 miles per hour,
    2. the vehicle is not being operated on an interstate highway, and
    3. no part of the load escapes from the vehicle. A driver shall immediately retrieve material that escapes from the vehicle, when safe to do so. A driver shall immediately retrieve material that escapes from the vehicle, when safe to do so.