Maximum Weight per Axle or Group of Axles Allowed — Exemptions for Heavy-Duty Tow and Recovery and Emergency Fire Suppression Vehicles

1. Law
2. Tennessee Code
3. Motor and Other Vehicles
4. Size, Weight and Load
5. Weight and Length Specifications
6. Maximum Weight per Axle or Group of Axles Allowed — Exemptions for Heavy-Duty Tow and Recovery and Emergency Fire Suppression Vehicles

1. Except as otherwise provided by law, no freight motor vehicle shall be operated over, on, or upon the public highways of this state where the total weight on a single axle or any group of axles exceeds the weight limitations set forth in subdivisions (b)(1)-(7).
2. 1. 1. No axle shall carry a load in excess of twenty thousand pounds (20,000 lbs.).
      2. Axle combinations and fifth wheel placement on the tractor shall ensure equal weight distribution on weight carrying axle combinations, and the axle combinations shall be equipped with brakes having power motivation.
      3. An axle load as set out herein is defined as the total load transmitted to the road by all wheels whose centers may be included between two (2) parallel transverse vertical planes, not more than forty inches (40") apart, extending across the full width of the vehicle.
   2. The total gross weight concentrated on the highway surface from any tandem axle group shall not exceed thirty-four thousand pounds (34,000 lbs.) for each tandem axle group. “Tandem axle group” means two (2) or more axles spaced more than forty inches (40") and not more than ninety-six inches (96") apart from center to center having at least one (1) common point of weight suspension.
   3. The total gross weight of a vehicle, freight motor vehicle, truck-tractor, trailer or semitrailer or combinations of these vehicles operated over, on or upon the public highways of this state shall not exceed eighty thousand pounds (80,000 lbs.); provided, that when operating over or on the interstate system of this state the total gross weight shall not exceed the lesser of eighty thousand pounds (80,000 lbs.) or the weight produced by application of the following formula:

      (Click here to view Equation)

      Where W = overall gross weight on any group of two (2) or more consecutive axles to the nearest five hundred pounds (500 lbs.), L = distance in feet between the extreme of any group of two (2) or more consecutive axles, and N = number of axles in group under consideration, except that two (2) consecutive sets of tandem axles may carry a gross load of thirty-four thousand pounds (34,000 lbs.) each, where the overall distance between the first and last axles of such consecutive sets of tandem axles is thirty-six feet (36') or more, except such vehicles, or combinations thereof operating under special permits now authorized by law; provided, that wherever a maximum permissive gross weight of eighty thousand pounds (80,000 lbs.) or of lengths prescribed in §55-7-201 or a height of thirteen and one-half feet (13 ½') is authorized for any vehicle or combination of vehicles, it is the legislative intent that the prescribed weight, length, and height limits shall be strictly enforced, and it is unlawful for any state, county, or municipal officer to allow or permit any additional weight, length or height by way of tolerance or otherwise, except that the commissioner of transportation may issue special permits pursuant to §55-7-205.

   4. “Freight motor vehicle,” as used in this section, includes both the tractor or truck and the trailer, semitrailer or trailers, if any, and the weight of any combination shall not exceed the maximum fixed herein; provided, that no freight motor vehicle with motive power shall haul more than one (1) vehicle unless otherwise provided.
   5. No freight motor vehicle shall haul a trailer on any highway of this state when the trailer (including its load) weighs more than three thousand five hundred pounds (3,500 lbs.). The restrictions on hauling a trailer in excess weight of three thousand five hundred pounds (3,500 lbs.) by a freight motor vehicle, as described in the preceding sentence, shall not be applicable whenever a converter dolly or equivalent fixed connection having the same safety characteristics is appropriately installed or placed under the trailer to be hauled by this freight motor vehicle. For the purposes of this subdivision (b)(5), “trailer” means a vehicle without motive power designed or used for carrying freight or property wholly on its own structure; provided, that it is not unlawful for any motor vehicle subject to this part to have a semitrailer, which, for the purposes hereof, is defined as a vehicle for the carrying of property or freight and so designed that some part of the weight of the semitrailer or its load rests upon or is carried by the motor vehicle to which it is attached. The hauling of a trailer (to the extent herein permitted) or a semitrailer shall be subject to the further provisions hereof. This part is not intended to prohibit the movements of spools carrying wire or cable, when used for construction or repair purposes. The weight limitation respecting trailers shall not be applicable to implements designed to distribute fertilizer while such vehicles are being drawn by a freight motor vehicle between the plant and the farm.
   6. If the gross weight of a freight motor vehicle does not exceed the sum obtained by computing the total weight allowable for the number and type of its axles, the driver shall not be cited for violation of an axle weight limitation while transporting crushed stone, fill dirt and rock, soil, bulk sand, coal, clay, shale, phosphate muck, asphalt, concrete, other building materials, solid waste, tankage or animal residues, livestock and agricultural products, or agricultural limestone over the state highway system other than the portion designated as the interstate system.
   7. For purposes of enforcement of this section, weight restrictions shall be deemed to have a margin of error of ten percent (10%) of the true gross or axle weight for all logging, sand, coal, clay, shale, phosphate, solid waste, recovered materials, farm trucks and machinery trucks when being operated over the state highway system other than the portion designated as the interstate system. For the purposes of this subdivision (b)(7):
      1. “Clay truck” means those trucks used for hauling clay from the place of extraction to the place where the clay is used or processed;
      2. “Coal truck” means those trucks used for hauling coal and coal products;
      3. “Farm truck” means those trucks utilized by farmers to load grain, fiber, produce, livestock, milk or other agricultural products produced on their farms and to transport the agricultural commodities to their respective markets. The trucks include farm to market transportation when the truck is operated by the farmer, the farmer's family or employee or a representative hired by the farmer to haul the commodity;
      4. “Logging truck” means those trucks used for hauling logs, pulpwood, bark, wood chips or wood dust from the woods to the mill or from the mill to a loading or storage place or market;
      5. “Machinery truck” means those trucks used for hauling machinery by the owner/operator within a one hundred (100) mile radius of the base location of the owner/operator's area of operation, subject to the limitation of one (1) truck per owner/operator;
      6. “Phosphate truck” means those trucks used for hauling phosphate, phosphate products, or other raw materials used in the manufacture of phosphorus;
      7. “Recovered materials truck” means those trucks used for hauling recovered materials, as defined in § 68-211-802, but only while those materials are being hauled from the point of generation to the facility where they will be processed for subsequent shipment to an end-user;
      8. “Sand truck” means those trucks used for hauling raw sand from the place of extraction to the place where the sand is used or processed; provided, that if the commissioner of transportation is formally notified by an appropriate federal officer that as a result of any provision of Acts 1989, ch. 349, adding sand trucks to this subdivision (b)(7) that Tennessee will lose federal funds, then such act shall be void and inoperative;
      9. “Shale truck” means those trucks used for hauling shale from the place of extraction to the place where the shale is used or processed; and
      10. “Solid waste truck” means those trucks used for hauling solid waste, as defined in § 68-211-802, but only while the solid waste is being collected and being hauled from the place or places of collection to a landfill or disposal facility.
   8. Notwithstanding the maximum weight provisions of this section, in order to promote the reduction of fuel use and emissions, the maximum gross vehicle weight limits and axle weight limits for any motor vehicle subject to subdivision (b)(3) and equipped with idle-reduction technology or other emissions-reduction technology shall be increased by the weight of the idle-reduction technology or emissions-reduction technology; provided, that such weight is not more than five hundred fifty pounds (550 lbs.) or the maximum amount allowed by federal law, whichever is greater. At the request of an authorized representative of the department of safety, the motor vehicle operator shall provide proof by means of documentation or by a physical inspection that the vehicle is equipped with such idle-reduction technology or other emissions-reduction technology.
   9. 1. To the extent required by federal law, a vehicle operated by an engine fueled primarily by natural gas may exceed any vehicle weight limit under this section, up to a maximum gross vehicle weight of eighty-two thousand pounds (82,000 lbs.), by an amount that is equal to the difference between:
         1. The weight of the vehicle attributable to the natural gas tank and fueling system carried by that vehicle; and
         2. The weight of a comparable diesel tank and fueling system.
      2. Subdivision (b)(9)(A) applies only when a vehicle is operating on the interstate highway system or within terminals and facilities for food, fuel, repairs, and rest with reasonable access to and from the interstate highway system.
3. For nondivisible overweight loads exceeding the maximum gross vehicle weight established in this section, the commissioner may issue a special permit in accordance with § 55-7-205 allowing axle weights in excess of the axle weight limits established in subsection (b) as follows:
   1. The maximum width of the vehicle, including the truck and semi-trailer or trailer combination, shall not exceed ten feet (10'); provided, however, that the load may exceed ten feet (10') in width if properly permitted;
   2. No single axle shall carry a load in excess of twenty-three thousand pounds (23,000 lbs.);
   3. No tandem axle group shall carry a load in excess of forty-six thousand pounds (46,000 lbs.); and
   4. No axle group of three (3) axles (tridem) shall carry a load in excess of sixty thousand pounds (60,000 lbs.).
4. 1. To the extent required by federal law, the vehicle weight limitations set forth in this section do not apply to a covered heavy-duty tow and recovery vehicle operating on the interstate highway system and within reasonable access to and from the interstate highway system to terminals and facilities for food, fuel, repairs, and rest.
   2. As used in this subsection (d), “heavy-duty tow and recovery vehicle” means a vehicle that:
      1. Is transporting a disabled vehicle from the place where the vehicle became disabled to the nearest appropriate repair facility; and
      2. Has a gross vehicle weight that is equal to or exceeds the gross vehicle weight of the disabled vehicle being transported.
5. 1. To the extent required by federal law, the vehicle weight limitations otherwise set forth in this section do not apply to an emergency fire suppression vehicle operating on the interstate highway system and within reasonable access to and from the interstate highway system to terminals and facilities for food, fuel, repairs, and rest. The following vehicle weight limitations shall apply instead:
      1. A maximum gross vehicle weight of eighty-six thousand pounds (86,000 lbs.);
      2. Twenty-four thousand pounds (24,000 lbs.) on a single steering axle;
      3. Thirty-three thousand five hundred pounds (33,500 lbs.) on a single drive axle;
      4. Sixty-two thousand pounds (62,000 lbs.) on a tandem axle; and
      5. Fifty-two thousand pounds (52,000 lbs.) on a tandem rear drive steer axle.
   2. As used in this subsection (e), “emergency fire suppression vehicle” means a vehicle designed to be used under emergency conditions:
      1. To transport personnel and equipment; and
      2. To support the suppression of fires and mitigation of other hazardous situations.
6. This section shall be enforced in accordance with all applicable provisions of federal law regarding the operation of vehicles.

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