§47-12-301.

§47-12-301.
   
   (a) Every motor vehicle, other than a motorcycle or motor-driven
   cycle, when operated upon a highway shall be equipped with brakes
   adequate to control the movement of and to stop and hold such vehicle,
   including two separate means of applying the brakes, each of which
   means shall be effective to apply the brakes to at least two wheels.
   If these two separate means of applying the brakes are connected in
   any way they shall be so constructed that failure of any one part of
   the operating mechanism shall not leave the motor vehicle without
   brakes on at least two wheels.
   
   (b) Repealed.
   
   (c) Every trailer, semitrailer, and pole trailer of a gross weight of
   three thousand pounds or more when operated upon a highway shall be
   equipped with brakes adequate to control the movement of and to stop
   and to hold such vehicle and so designated as to be applied by the
   driver of the towing motor vehicle from its cab, and said brakes shall
   be so designed and connected that in case of an accidental breakaway
   of the towed vehicle the brakes shall be automatically applied.
   
   (d) Every new motor vehicle, trailer or semitrailer hereafter sold in
   this state and operated upon the highways shall be equipped with
   service brakes upon all wheels of every such vehicle, except
   motorcycles or motor-driven cycles, and semitrailers of less than
   three thousand (3,000) pounds gross weight, provided that trucks and
   truck tractors having three or more axles need not have brakes on the
   front axle, except when such vehicles are equipped with at least two
   steerable axles, the axles of one such axle need not be equipped with
   brakes.
   
   (e) Every singly-driven motor vehicle and every combination of motor
   vehicles shall be equipped with parking brakes adequate to hold a
   vehicle or combination on any grade on which it is operated under any
   condition of loading, on a surface free from snow or ice.
   
   (f) The brake shoes operating within or upon the drums on the vehicle
   wheels of any motor vehicle may be used for both service and hand
   operation.
   
   (g) 1. Every full trailer, semitrailer and pole trailer required to be
   equipped with brakes, except motor vehicles engaged in drive-away,
   tow-away operations, shall be equipped with brakes of such a character
   as to be applied automatically and promptly upon break-away from the
   towing vehicle, and means shall be provided to maintain application of
   the brakes on the trailer in such a case for at least fifteen (15)
   minutes. Air brake systems installed on towed vehicles manufactured
   after the effective date of this act shall be so designed, by the use
   of "no-bleed-back" relay-emergency valves or equivalent devices, that
   the supply reservoir used to provide air for brakes shall be
   safeguarded against backflow of air from the reservoir through the
   supply line. After the effective date of this act, every truck or
   truck tractor, if used to tow a trailer equipped with brakes, shall be
   equipped with means for providing that in case of break-away of such
   trailer the service brakes on the towing vehicle will be sufficiently
   operative to stop the towing vehicle. Every truck or truck tractor
   equipped with air brakes, the date of manufacture of which is
   subsequent to the effective date of this act, and every truck or truck
   tractor equipped with air brakes on and after the effective date of
   this act, when used to tow another vehicle equipped with full air
   brakes, in operations other than drive-away or tow-away, shall, in
   addition to the above, be equipped with two means of activating the
   emergency features of the trailer brakes. One of these means shall
   operate automatically in the event of reduction of the towing vehicle
   air supply to a fixed pressure which shall be not lower than twenty
   (20) pounds per square inch nor higher than forty-five (45) pounds per
   square inch. The other means shall be a manually controlled device
   readily operable by a person seated in the driving seat, and its
   emergency position or method of operation shall be clearly indicated.
   In no instance may the manual means be so arranged as to permit its
   use to prevent operation of the automatic means. The automatic and
   manual means of application required by this section may be, but are
   not required to be, separate.
   
   2. Every truck tractor and truck manufactured after the effective date
   of this act, which is equipped with power brakes, shall have the
   braking system so arranged that one application valve shall, when
   applied, operate all the service brakes on the truck tractor and truck
   or combination thereof. This requirement shall not be construed to
   prohibit a truck tractor or truck from being equipped with an
   additional valve to be used to operate the brakes on a trailer or
   trailers or as provided in subparagraph 1. of this section. This rule
   shall not be applicable to drive-away, tow-away operations unless the
   brakes on such operations are designed to be operated by a single
   valve.
   
   3. Every truck tractor and truck used for towing other vehicles
   equipped with vacuum brakes, in operations other than drive-away and
   tow-away on and after the effective date of this act, shall have, in
   addition to the single control device as provided by subparagraph 2.
   of this section to operate all brakes of the combination, a second
   control device independent of brake air, hydraulic, or other pressure
   and independent of other controls, which can be used to operate the
   brakes on the towed vehicles in emergencies. Such second control is
   not required by this rule to provide modulated or graduated braking.
   
   (h) Every bus, truck and truck tractor manufactured after the
   effective date of this act, which is equipped with an air or vacuum
   brake system, shall be equipped with reserve capacity or a reservoir
   sufficient to insure a brake application capable of stopping the
   vehicle within the stopping distance requirements of Section 12-302 of
   this act in the event the engine stops. No such reserve capacity or
   reservoir shall be required on single vehicles if the braking system
   is so designed and installed as to provide for application of the
   service brakes through hydraulic or mechanical means in event of
   failure of the air or vacuum system or the source of supply of such
   systems. In addition, every truck tractor and every truck used for
   towing other vehicles shall, when equipped with air or vacuum
   reservoirs as required by this section, and regardless of date of
   manufacture, have such air or vacuum reservoirs so safeguarded by a
   check value or equivalent device that in the event of failure or
   leakage in its connection to the source of compressed air or vacuum
   the air or vacuum supply in the reservoir shall not be depleted by the
   leak or failure.
   
   (i) Every bus, truck and truck tractor equipped with an air brake
   system, and, on and after the effective date of this act, every truck
   tractor and every truck used for towing a vehicle required to have
   brakes, if the brakes are vacuum-operated, shall be provided with
   either an audible or visible warning signal to indicate readily to the
   driver any loss or lack of air or vacuum sufficient to prevent the
   vehicle from being stopped. A gauge indicating pressure or vacuum
   shall not be deemed to be an adequate means of satisfying this
   requirement.