Alabama Axle Weight Limits

Maximum Legal Weight Allowed

1. The gross weight imposed on the highway by the wheels of any one axle of a vehicle shall not exceed 20,000 pounds, or such other weight, if any, as may be permitted by federal law to keep the state from losing federal funds; provided, that inadequate bridges shall be posted to define load limits.
2. For the purpose of this section, an axle load shall be defined as the total load transmitted to the road by all wheels whose centers are included between two parallel transverse vertical planes 40 inches apart, extending across the full width of the vehicle.

Except as provided by special permits, no vehicle or combination of vehicles exceeding the gross weights specified above shall be permitted to travel on the public highways within the State of Alabama.

No vehicle or combination of vehicles shall be permitted to operate on any portion of the Interstate Highway System of Alabama that shall have a greater weight than 20,000 pounds carried on any one axle, including all enforcement tolerances, or with a tandem axle weight in excess of 34,000 pounds, including all enforcement tolerances, or with an overall gross weight on a group of two or more consecutive axles produced by application of the following formula:

W = 500 (LN/(N-1) + 12N + 36)

W = overall gross weight on any group of two or more consecutive axles to the nearest 500 pounds,
L = distance in feet between the extreme of any group of two or more consecutive axles,
N = number of axles in group under consideration.

Except, that two consecutive sets of tandem axles may carry a gross load of 34,000 pounds each, provided the overall distance between the first and last axles of the consecutive sets of tandem axles is 36 feet or more; provided, that the overall gross weight may not exceed 80,000 pounds, including all enforcement tolerances.

All weights less than or equal to the sum of the weight otherwise prescribed by this subdivision, plus an additional weight to be calculated by multiplying the weight prescribed by this subdivision by one-tenth (.10) that shall represent a scale or enforcement tolerance, shall be deemed to be in compliance with the requirements of this section, and shall not constitute violations thereof.

Dump trucks, dump trailers, concrete mixing trucks, fuel oil, gasoline trucks, and trucks designated and constructed for special type work or use shall not be made to conform to the axle spacing requirements; provided, that the vehicle shall be limited to a weight of 20,000 pounds per axle plus scale tolerances; and, provided further, that the maximum gross weight of the vehicles shall not exceed the maximum weight allowed by this section for the appropriate number of axles, irrespective of the distance between axles, plus allowable scale tolerances. All axles shall be brake equipped. Trucks delivering asphalt plant mix which do not exceed the maximum allowable gross weight and operate within 50 miles of their home base shall not be required to conform to the requirements mentioned above. Concrete mixing trucks which operate within 50 miles of their home base and do not exceed the maximum allowable gross weight shall not be required to conform to the requirements mentioned above. It shall be a violation if the vehicles named under this subdivision travel upon bridges designated and posted by the Transportation Director as incapable of carrying the load.

Axle Weight  Distribution:

If any one axle in the group exceeds 20,000 pounds in weight, it shall not exceed the weight of any other axle in the group by more than 50 percent.

Two and three axle vehicles being used exclusively for the purpose of transporting agricultural commodities or products to and from a farm and for agricultural purposes relating to the operation and maintenance of a farm by any farmer, custom harvester or husbandman may not be made to conform to the axle requirements or the gross weight requirements.

1. Any vehicle utilizing an auxiliary power or idle reduction technology unit in order to promote reduction of fuel use and emissions because of engine idling shall be allowed an additional 400 pounds total to the gross, axle, tandem, or bridge formula weight limits defined in this section.
2. To be eligible for the exception provided in this subsection, the operator of the vehicle must provide written proof or certification of the weight of the auxiliary power unit (APU) and demonstrate or certify the idle reduction technology is fully functional at all times.
3. Written proof or certification of the weight of the APU must be available to law enforcement officers if the vehicle is found in violation of applicable weight laws. The weight allowed cannot exceed 400 pounds or the actual weight proven or certified, whichever is less.

Exemptions:

There shall be exempt from the provisions of this article as to weight any truck or semitrailer truck transporting milk for human consumption, for which refrigeration and transit is reasonably necessary in the interest of public health, when moving under refrigeration to or from market from the territory in which such commodity is collected or concentrated.

Any provision of any other law or the provision of any administrative rule, regulation, or order to the contrary notwithstanding, it shall be lawful for any farmer, custom picker, or husbandman to operate a two to eight-wheel, one to four-axle trailer on the highways of this state if the trailer is being used exclusively for the purpose of transporting to and from a farm agricultural commodities or products and for agricultural purposes relating to the operation and maintenance of a farm; provided, that the combined weight of the trailer and its load is not in excess of 36,000 pounds, nor more than 10,000 pounds per axle, whichever is less.

Maximum Permit Weight Allowed

An annual or single trip permit shall not authorize the operation of a vehicle including all enforcement tolerances: if total gross weight exceeds 150,000 pounds; provided, that gross weights over 100,000 pounds shall require advance routing by the department; if single axle weight exceeds 22,000 pounds.

Exception

An annual permit may be issued to operate a vehicle which exceeds the maximum limits otherwise provided in this article for rubber-tired equipment used solely in the scope and operation of mining refractory grade bauxite. The equipment may not exceed the limits mentioned above, except that the permit may not authorize the operation of a vehicle, including enforcement tolerances, which exceeds 16 feet in width, exceeds 18 feet in height, or exceeds a single axle weight of 27,000 pounds. In addition, the permit may not authorize the operation of the vehicle on any bridge, over or under any overpass, or on an interstate highway.

Source: https://www.dot.state.al.us/maweb/Oversize&OverweightPermitInformation.html
Source: Oversize.io