Vehicles operating under a permit must stay within the axle weight limits stated here, with several special exceptions.
1. The gross weight on any 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 for the following: a. Cranes being temporarily moved on streets, roads, or highways may have a gross weight of twenty-four thousand pounds on any single axle. b. (1) Special mobile equipment other than cranes being temporarily moved on streets, roads, or highways may have a maximum gross weight of thirty-six thousand pounds on any single axle equipped with flotation pneumatic tires with a minimum size of twenty-six point five inches by twenty-five inches and a maximum gross weight of twenty thousand pounds on any single axle equipped with flotation pneumatic tires with a minimum size of eighteen inches by twenty-five inches. (2) The department is authorized to adopt rules to permit the use of tire sizes and weights within the minimum and maximum specifications provided in subparagraph (1), provided that the total gross weight of the vehicle or combination of vehicles does not exceed one hundred twenty-six thousand pounds. (3) 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. c. 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. d. 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. e. Vehicles operating under a permit issued pursuant to section 321E.8, 321E.9, 321E.9A, or 321E.26 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 forty-six thousand pounds on a single tandem axle of the trailer or semitrailer if each axle of each tandem group has at least four tires. 2. 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. 3. 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. [C31, 35, §5067-d7, -d8; C39, §5035.16; C46, 50, 54, 58, 62, 66, §321.467; C71, 73, 75, 77, 79, 81, §321E.7] 83 Acts, ch 116, §4; 96 Acts, ch 1089, §7, 8; 96 Acts, ch 1152, §20; 97 Acts, ch 100, §7; 2003 Acts, ch 8, §20, 29; 2007 Acts, ch 143, §19; 2008 Acts, ch 1124, §10; 2013 Acts, ch 49, §4; 2016 Acts, ch 1098, §35; 2019 Acts, ch 15, §3; 2019 Acts, ch 158, §3 Referred to in §321.463, 321E.2, 321E.8, 321E.9, 321E.9A, 321E.14, 321E.26