(a) Compliance. Every motor carrier and its officers, agents, drivers, representatives and employees directly concerned with the installation and maintenance of equipment and accessories shall comply and be conversant with the requirements and specifications of this part, and no motor carrier shall operate any motor vehicle, or cause or permit it to be operated, unless it is equipped in accordance with said requirements and specifications.

(b) Lighting devices. Every motor vehicle shall be equipped with the lighting devices and reflectors required by subpart B of part 393 of this subchapter.

(c) Brakes. Every motor vehicle shall be equipped with brakes as required by subpart C of part 393 of this subchapter, except §393.44 of this subchapter, and shall satisfy the braking performance requirements contained therein.

(d) Coupling devices; fifth wheel mounting and locking. The lower half of every fifth wheel mounted on any truck-tractor or dolly shall be securely affixed to the frame thereof by U-bolts of adequate size, securely tightened, or by other means providing at least equivalent security. Such U-bolts shall not be of welded construction. The installation shall be such as not to cause cracking, warping, or deformation of the frame. Adequate means shall be provided positively to prevent the shifting of the lower half of a fifth wheel on the frame to which it is attached. The upper half of every fifth wheel shall be fastened to the motor vehicle with at least the security required for the securing of the lower half to a truck-tractor or dolly. Locking means shall be provided in every fifth wheel mechanism including adapters when used, so that the upper and lower halves may not be separated without the operation of a positive manual release. A release mechanism operated by the driver from the cab shall be deemed to meet this requirement. On fifth wheels designed and constructed as to be readily separable, the fifth wheel locking devices shall apply automatically on coupling for any motor vehicle the date of manufacture of which is subsequent to December 31, 1952.

(e) Tires. Every motor vehicle shall be equipped with tires of adequate capacity to support its gross weight. No motor vehicle shall be operated on tires which have been worn so smooth as to expose any tread fabric or which have any other defect likely to cause failure. No vehicle shall be operated while transporting passengers while using any tire which does not have tread configurations on that part of the tire which is in contact with the road surface. No vehicle transporting passengers shall be operated with re-grooved, re-capped, or re-treaded tires on front wheels.

(f) Passenger compartment. Every motor vehicle transporting passengers, other than a bus, shall have a passenger compartment meeting the following requirements:

(1) Floors. A substantially smooth floor, without protruding obstructions more than two inches high, except as are necessary for securing seats or other devices to the floor, and without cracks or holes.

(2) Sides. Side walls and ends above the floor at least 60 inches high, by attachment of sideboards to the permanent body construction if necessary. Stake body construction shall be construed to comply with this requirement only if all six-inch or larger spaces between stakes are suitably closed to prevent passengers from falling off the vehicle.

(3) Nails, screws, splinters. The floor and the interior of the sides and ends of the passenger-carrying space shall be free of inwardly protruding nails, screws, splinters, or other projecting objects likely to be injurious to passengers or their apparel.

(4) Seats. On and after November 1, 1957, a seat shall be provided for each worker transported. The seats shall be: Securely attached to the vehicle during the course of transportation; not less than 16 inches nor more than 19 inches above the floor; at least 13 inches deep; equipped with backrests extending to a height of at least 36 inches above the floor, with at least 24 inches of space between the backrests or between the edges of the opposite seats when face to face; designed to provide at least 18 inches of seat for each passenger; without cracks more than two inches wide, and the exposed surfaces, if made of wood, planed or sanded smooth and free of splinters.

(5) Protection from weather. Whenever necessary to protect the passengers from inclement weather conditions, be equipped with a top at least 80 inches high above the floor and facilities for closing the sides and ends of the passenger-carrying compartment. Tarpaulins or other such removable devices for protection from the weather shall be secured in place.

(6) Exit. Adequate means of ingress and egress to and from the passenger space shall be provided on the rear or at the right side. Such means of ingress and egress shall be at least 18 inches wide. The top and the clear opening shall be at least 60 inches high, or as high as the side wall of the passenger space if less than 60 inches. The bottom shall be at the floor of the passenger space.

(7) Gates and doors. Gates or doors shall be provided to close the means of ingress and egress and each such gate or door shall be equipped with at least one latch or other fastening device of such construction as to keep the gate or door securely closed during the course of transportation; and readily operative without the use of tools.

(8) Ladders or steps. Ladders or steps for the purpose of ingress or egress shall be used when necessary. The maximum verticle spacing of footholds shall not exceed 12 inches, except that the lowest step may be not more than 18 inches above the ground when the vehicle is empty.

(9) Hand holds. Hand holds or devices for similar purpose shall be provided to permit ingress and egress without hazard to passengers.

(10) Emergency exit. Vehicles with permanently affixed roofs shall be equipped with at least one emergency exit having a gate or door, latch and hand hold as prescribed in paragraphs (f) (7) and (9) of this section and located on a side or rear not equipped with the exit prescribed in paragraph (f)(6) of this section.

(11) Communication with driver. Means shall be provided to enable the passengers to communicate with the driver. Such means may include telephone, speaker tubes, buzzers, pull cords, or other mechanical or electrical means.

(g) Protection from cold. Every motor vehicle shall be provided with a safe means of protecting passengers from cold or undue exposure, but in no event shall heaters of the following types be used:

(1) Exhaust heaters. Any type of exhaust heater in which the engine exhaust gases are conducted into or through any space occupied by persons or any heater which conducts engine compartment air into any such space.

(2) Unenclosed flame heaters. Any type of heater employing a flame which is not fully enclosed.

(3) Heaters permitting fuel leakage. Any type of heater from the burner of which there could be spillage or leakage of fuel upon the tilting or overturning of the vehicle in which it is mounted.

(4) Heaters permitting air contamination. Any heater taking air, heated or to be heated, from the engine compartment or from direct contact with any portion of the exhaust system; or any heater taking air in ducts from the outside atmosphere to be conveyed through the engine compartment, unless said ducts are so constructed and installed as to prevent contamination of the air so conveyed by exhaust or engine compartment gases.

(5) Any heater not securely fastened to the vehicle.

[33 FR 19765, Dec. 25, 1968, as amended at 77 FR 59828, Oct. 1, 2012]