Ariz. Rev. Stat. § 28-1100 – Vehicles and loads; gross weight restrictions; exceptions

A. Except as provided in subsection H of this section or section 28-1099, a person may operate a vehicle on all highways, including a toll facility as defined in section 28-7751, subject to the following maximum gross weights:
1. 1. Twenty thousand pounds, including enforcement tolerances, on any one axle.
2. 2. Thirty-four thousand pounds, including enforcement tolerances, on a tandem axle.
3. 3. Eighty thousand pounds on a vehicle combination of five axles or more.
4. 4. On a group of two or more consecutive axles, including any steering or castering axles, an overall gross weight, including enforcement tolerances, produced by application of the following formula in which W equals overall gross weight on any group of two or more consecutive axles to the nearest five hundred pounds, L equals distance in feet between the extreme of any group of two or more consecutive axles to the nearest foot and N equals number of axles in any group under consideration, except that two consecutive sets of tandem axles may carry a gross load of thirty-four thousand pounds each if the overall distance between the first and last axles of the consecutive sets of tandem axles is thirty-six feet or more if the overall gross weight does not exceed eighty thousand pounds, including all enforcement tolerances:
  W = 500 (LN/(N-1) + 12N + 36)
B. For the purposes of subsection A of this section, "tandem axles" means two or more consecutive axles that are more than forty inches but not more than ninety-six inches apart.
C. This section does not apply to a vehicle and load that cannot be easily dismantled or divided and that have been issued a special permit pursuant to section 28-1103.
D. It is not a defense in a prosecution for a violation of this section that a vehicle or vehicle combination is registered for a declared gross weight as defined in section 28-5431 in excess of the amount allowed under this section. The department shall not make an allowance or refund for fees paid for the weight in excess of the amount allowed under this section.
E. A single vehicle or a single vehicle of a combination of vehicles shall not be equipped with more than three axles, including the front steering axle, unless the additional axles are steering axles or castering axles. The limitation on the number of axles provided in this subsection does not apply to a vehicle operated with a permit issued pursuant to section 28-1103.
F. A vehicle or combination of vehicles equipped with one or more variable load axles shall have the pressure control preset and located outside of the cab so that the operator of the vehicle cannot vary the weight carried on the variable load axle or axles during transport of a load. The actuating control that raises or lowers the axle or axles may be located inside the cab for safety purposes. This actuating control must completely raise or completely lower the axle or axles when activated.
G. This section does not apply to a truck that meets all of the following requirements and for which a special permit has been issued pursuant to section 28-1103:
1. 1. Is equipped with a conveyor bed.
2. 2. Is used solely as a fiber and forage module mover.
3. 3. Does not exceed forty-eight feet in length.
4. 4. Is only operated each year from August 1 through January 30, unless the director extends the period of use.
H. The gross weight of a heavy-duty vehicle that is equipped with idle reduction technology and the gross weight imposed on the highway by the wheels of any one axle or axle group of the vehicle may exceed the weight limitation specified in subsection A of this section by not more than five hundred fifty pounds or the weight of the idle reduction technology, whichever is less. This subsection only applies if the heavy-duty vehicle operator, on request, proves by written certification the weight of the idle reduction technology and, by demonstration or certification, that the idle reduction technology is fully functional at all times. For the purposes of this subsection, "heavy-duty vehicle" and "idle reduction technology" have the same meanings prescribed in 42 United States Code section 16104a.
I. The gross weight of a vehicle operated by an engine fueled primarily by natural gas, battery electric, or hydrogen and the gross weight imposed on the highway by the wheels of any one axle or axle group of the vehicle may exceed the weight limitation specified in subsection A of this section, but may not exceed eighty-two thousand pounds or an amount that is equal to the difference between the weight of the vehicle attributable to the natural gas tank and fueling system or battery electric or hydrogen fuel cell electric fueling system and the weight of a comparable diesel tank and fueling system, whichever is less.