Colorado Revised Statutes Title 42. Vehicles and Traffic § 42-4-1407.5. Splash guards--when required--definition

(a) “Splash guards” means mud flaps, rubber, plastic or fabric aprons, or other devices directly behind the rear-most wheels, designed to minimize the spray of water and other substances to the rear.

(b) “Splash guards” must, at a minimum, be wide enough to cover the full tread of the tire or tires being protected, hang perpendicular from the vehicle not more than ten inches above the surface of the street or highway when the vehicle is empty, and generally maintain their perpendicular relationship under normal driving conditions.

(a) Passenger-carrying motor vehicles registered pursuant to section 42-3-306(2);

(b) Trucks and truck tractors registered pursuant to section 42-3-306(4) or (5) having an empty weight of ten thousand pounds or less;

(c) Trailers equipped with fenders or utility pole trailers;

(d) Vehicles while involved in chip and seal or paving operations or road widening equipment;

(e) Truck tractors or converter dollies when used in combination with other vehicles;

(f) Vehicles drawn by animals; or

(g) Bicycles, electrical assisted bicycles, or electric scooters.