Every truck, truck-tractor, trailer, semitrailer, pole trailer, and rear-end dump truck, excepting rear-end dump farm trucks, must be provided with wheel flaps or other suitable protection above and behind the rearmost wheels of the vehicle or combination of vehicles to prevent, as far as practicable, the wheels from throwing dirt, water, or other materials on the windshields of following vehicles. The flaps or protectors must be at least as wide as the tires they are protecting and have a ground clearance of not more than nine inches from the ground when the vehicle is empty.
For a dump truck or truck with a rigid box fastened to its frame and having a conveyor belt or chain in the bottom of the vehicle that moves the cargo to the rear end of the vehicle, the flaps must be mounted as far to the rear of the vehicle as practicable and have a ground clearance of not more than 18 inches when the vehicle is loaded.
In addition to meeting the requirements of subdivision 1, a bottom-dump cargo vehicle transporting sand, gravel, aggregate, dirt, lime rock, silica, or similar material must be equipped with a center flap between the wheel flaps, which must have a ground clearance of six inches or less when the vehicle is fully loaded.
If the motor vehicle is so designed and constructed that the above requirements are accomplished by means of body construction or other means of enclosure, then no protectors or flaps are required.
If the rear wheels are not covered at the top by fenders, body or other parts of the vehicle, the flap or other protective means must be extended at least to a point directly above the center of the rearmost axle.