Missouri Revised Statutes – § 307.170. — Other equipment of motor vehicles–violations, penalty.
307.170. 1. Signaling devices: Every motor vehicle shall be equipped with a horn, directed forward, or whistle in good working order, capable of emitting a sound adequate in quantity and volume to give warning of the approach of such vehicle to other users of the highway and to pedestrians. Such signaling device shall be used for warning purposes only and shall not be used for making any unnecessary noise, and no other sound-producing signaling device shall be used at any time.
2. Muffler cutouts: Muffler cutouts shall not be used and no vehicle shall be driven in such manner or condition that excessive and unnecessary noises shall be made by its machinery, motor, signaling device, or other parts, or by any improperly loaded cargo. The motors of all motor vehicles shall be fitted with properly attached mufflers of such capacity or construction as to quiet the maximum possible exhaust noise as completely as is done in modern gas engine passenger motor vehicles. Any cutout or opening in the exhaust pipe between the motor and the muffler on any motor vehicle shall be completely closed and disconnected from its operating lever, and shall be so arranged that it cannot automatically open, or be opened or operated while such vehicle is in motion.
3. Brakes: All motor vehicles, except motorcycles, shall be provided at all times with two sets of adequate brakes, kept in good working order, and motorcycles shall be provided with one set of adequate brakes kept in good working order.
4. Mirrors: All motor vehicles which are so constructed or loaded that the operator cannot see the road behind such vehicle by looking back or around the side of such vehicle shall be equipped with a mirror so adjusted as to reveal the road behind and be visible from the operator’s seat.
5. Projections on vehicles: All vehicles carrying poles or other objects, which project more than five feet from the rear of such vehicle, shall, during the period when lights are required by this chapter, carry a red light at or near the rear end of the pole or other object so projecting. At other times a red flag or cloth, not less than sixteen inches square, shall be displayed at the end of such projection.
6. Towlines: When one vehicle is towing another, the connecting device shall not exceed fifteen feet. During the time that lights are required by sections 307.020 to 307.120, the required lights shall be displayed by both vehicles. Every towed vehicle shall be coupled to the towing vehicle by means of a safety chain, cable, or equivalent device in addition to the primary coupling device, except that such secondary coupling device shall not be necessary if the connecting device is connected to the towing vehicle by a center-locking ball located over or nearly over the rear axle and not supported by the rear bumper of the towing vehicle. Such secondary safety connecting devices shall be of sufficient strength to control the towed vehicle in the event of failure of the primary coupling device. The provisions of this subsection shall not apply to wreckers towing vehicles or to vehicles secured to the towing vehicle by a fifth-wheel type connection.
7. The provisions of subsection 6 of this section shall not apply to farm implements, or to any vehicle which is not required to be registered.
8. Commercial motor vehicles and trailers: When being operated on any highway of this state shall be equipped with adequate and proper brakes, lighting equipment, signaling devices, steering mechanisms, horns, mirrors, windshield wipers, tires, wheels, exhaust system, glazing, air pollution control devices, fuel tank, and any other safety equipment required by the state in such condition so as to obtain a certificate of inspection and approval as required by the provisions of section 307.360.
9. Devices attached to or towed by motor vehicles for the purpose of transporting hay shall have the protruding parts raised or retracted when not in use to a position which will not cause injury or damage to persons or property in the vicinity of such device when on the highways of this state.
10. Violation of this section shall be deemed an infraction.