Iowa Axle Weight Limits

Maximum Legal Weight Allowed

For determining allowable vehicle weight limits, Iowa roadways are categorized into two specific groups, Non-Primary Highway System and Primary Highway System. The Non-Primary Highway System includes all city and county roads. The Primary Highway System includes all state and federal highways, and the Interstate Highway System.

At the request of any peace officer, Iowa law requires a vehicle to be weighed to determine compliance with the applicable weight limits. Consult the following information and wheelbase tables to determine the maximum vehicle axle, group and gross weights for the different truck configurations on the Non-Primary Highway System and Primary Highway System.

Federal rules provide an exception to maximum weight limits for a vehicle equipped with an auxiliary power unit (APU). A vehicle equipped with an operational APU may exceed the legal single, tandem, group or gross weight limit by the certified weight of the APU, up to a maximum of 550 pounds.

Country and City Non-Primary Highways

Single axle – 20,000 pounds
Tandem axle – 34,000 pounds
Maximum gross weight up to 86,000 pounds for a five-axle tractor/spread axle semitrailer transporting livestock
Maximum gross weight up to 90,000 pounds for six-axle vehicles
Maximum gross weight up to 96,000 pounds for seven or more axle vehicles

State and Federal Non-Interstate Primary Highways

Single axle – 20,000 pounds
Tandem axle – 34,000 pounds
Maximum gross weight up to 86,000 pounds for a five-axle tractor/spread axle semitrailer transporting livestock
Maximum gross weight up to 90,000 pounds for six-axle vehicles
Maximum gross weight up to 96,000 pounds for seven or more axle vehicles

Interstate Primary Highways

Single axle – 20,000 pounds
Tandem axle – 34,000 pounds
Maximum gross weight of 80,000 pounds

Tire weight rating: The tire manufacturer’s specified safe load capacity for the tire, as marked on the tire sidewall. Do not exceed the tire weight rating in either single or dual applications.

Maximum Permit Weight Allowed

Annual oversize/overweight permits

For movement under an annual oversize/overweight permit, the gross weight on any axle shall not exceed 20,000 pounds, with a maximum of 156,000 pounds total gross weight.

Multitrip permits

For movement under a multitrip permit, the gross weight on any axle shall not exceed 20,000 pounds with a maximum of 156,000 pounds total gross weight.

Single-trip permits

1. For movement under a single-trip permit, the gross weight on any axle shall not exceed 20,000 pounds.
2. If the combined gross weight exceeds 100,000 pounds, a single-trip permit may be issued for the movement only if the permit-issuing authority determines that it would not cause undue damage to the road and is in the best interest of the public.
3. Cranes may have a maximum of 24,000 pounds per axle for movement under a single-trip permit. Routes must be reviewed by the permit-issuing authority prior to issuance.

Special mobile equipment

Special mobile equipment may have a gross weight of 36,000 pounds on any single axle equipped with minimum size 26.5-inch by 25-inch flotation pneumatic tires and a maximum gross weight of 20,000 pounds on any single axle equipped with minimum size 18-inch by 25-inch flotation pneumatic tires, provided that the total gross weight of the vehicle or a combination of vehicles does not exceed a maximum of 80,000 pounds for movement under an annual or all-systems permit and 126,000 pounds for movement under a single-trip, multitrip or annual oversize/overweight permit.

For tire sizes and weights allowed between the maximum and minimum indicated, the following formula shall apply: Axle weight = 20,000 pounds + (tire width – 18) × 1,882 pounds

Exceptions

• Cranes being temporarily moved on streets, roads, or highways may have a gross weight of 24,000 pounds on any single axle.
• Special mobile equipment other than cranes being temporarily moved on streets, roads, or highways may have a maximum gross weight of 36,000 pounds on any single axle equipped with flotation pneumatic tires with a minimum 6 of 26.5 any single axle equipped with flotation pneumatic tires with a minimum size of 18 inches by 25 inches.
• The department is authorized to adopt rules to permit the use of tire sizes and weights within the minimum and maximum specifications provided that the total gross weight of the vehicle or combination of vehicles does not exceed 126,000 pounds.
• A manufacturer of machinery or equipment manufactured or assembled in Iowa may be granted a permit for the movement of such machinery or equipment mounted on pneumatic tires with axle loads exceeding the maximum axle load prescribed in section 321.463 for distances not to exceed twenty-five miles at a speed not greater than twenty miles per hour. The movement of such machinery or equipment shall be over a specified route between the place of assembly or manufacture and a storage area, shipping point, proving ground, experimental area, weighing station, or another manufacturing plant.
• Raw milk transporters operating under a permit issued pursuant to section 321E.29A shall not exceed the axle and gross weights specified in that section.
• Compacted rubbish vehicles operating under a permit issued pursuant to section 321E.30 shall not exceed the axle and gross weights specified in that section.
• Vehicles operating under a permit issued pursuant to section 321E.8, 321E.9, or 321E.9A may have a gross weight not to exceed forty-six thousand pounds on a single tandem axle of the truck tractor and a gross weight not to exceed 46,000 pounds on a single tandem axle of the trailer or semitrailer if each axle of each tandem group has at least four tires.
• The gross weight on any one axle of any vehicle or combination of vehicles traveling under a permit issued in accordance with this chapter shall not exceed the maximum axle load prescribed in section 321.463; except that any one axle on a vehicle or combination of vehicles transporting special mobile equipment shall be allowed a one thousand pound weight tolerance, provided the total gross weight of the vehicle or combination of vehicles does not exceed the gross weight allowed by the permit.
• Special mobile equipment, as defined in section 321.1, subsection 74, is not subject to the requirements for distance in feet between the extremes of any group of axles or the extreme axles of the vehicle or combination of vehicles as required by this chapter when being moved upon the highways if the operator has a permit issued under this chapter.
• Notwithstanding subsections 1 and 2, a self-propelled implement of husbandry traveling under a permit issued pursuant to section 321E.8A may exceed the maximum axle loads prescribed under section 321.463 only when operated on a non-interstate highway in a county covered under the permit, provided the weight on any one axle does not exceed twenty-five thousand pounds, and provided the current and valid permit is carried in the vehicle. However, a vehicle traveling under a permit issued pursuant to section 321E.8A is not exempt from posted weight limitations on bridges.

Source: https://iowadot.gov/mvd/motorcarriers/motorcarriers/osowpermits-determine
Source: https://iowadot.gov/mvd/motorcarriers/truckguide.pdf
Source: https://www.legis.iowa.gov/docs/code/321e.pdf
Source: https://www.legis.iowa.gov/docs/ACO/chapter/761.511.pdf
Source: Oversize.io