Yes, they are required. See Missouri Revised Statutes, Chapter 307, Vehicle Equipment Regulations, Section 307.015
307.015. 1. Trucks, semitrailers, and trailers, except utility trailers, without rear fenders, attached to a commercial motor vehicle registered for over twenty-four thousand pounds shall be equipped with mud flaps for the rear wheels when operated on the public highways of this state. If mud flaps are used, they shall be wide enough to cover the full tread width of the tire or tires being protected; shall be so installed that they extend from the underside of the vehicle body in a vertical plane behind the rear wheels to within eight inches of the ground; and shall be constructed of a rigid material or a flexible material which is of a sufficiently rigid character to provide adequate protection when the vehicle is in motion. No provisions of this section shall apply to a motor vehicle in transit and in process of delivery equipped with temporary mud flaps, to farm implements, or to any vehicle which is not required to be registered.
For interstate carriers, yes. For intrastate carriers, it's going to vary by state.
All trucks and trailers with four or more tires on the rear axel must have safety guards or mud flaps behind the rear wheel.
yes if it is on an 18 wheeler trailer or tractor
are bob tailing truck tractors required mud flaps
§ 547.606. SAFETY GUARDS OR FLAPS REQUIRED. (a) A roadtractor, truck, trailer, truck-tractor in combination with asemitrailer, or semitrailer in combination with a towing vehiclethat has at least four tires on the rearmost axle of the vehicle orthe rearmost vehicle in the combination shall be equipped withsafety guards or flaps that:(1) are of a type prescribed by the department; and(2) are located and suspended behind the rearmostwheels of the vehicle or the rearmost vehicle in the combinationwithin eight inches of the surface of the highway.(b) This section does not apply to a truck-tractor operatedalone or a pole trailer.
That law tends to vary by state. In North Carolina, you're not actually required to have mud flaps. Other states may require it. I've never seen anything in the FMCSR pertaining to mud flaps, and it's unlikely that the feds mandate it, considering that states have leeway in determining whether or not they want to make them mandatory.
no
Yes.
Mud flaps have to be on medium and heavy duty trucks in Pennsylvania. This is the law and you can be fined if they aren't.
Mud flaps are required on commercial vehicles in all states.
are truck tractors required mud flaps
If the tires are not inside the wheel well opoenings then yes.