The gross load imposed on the highway by any vehicle or combination of vehicles shall not exceed the limits in this section. The maximum single axle gross weight shall be twenty thousand (20,000) pounds, the maximum single wheel gross weight shall be ten thousand (10,000) pounds and the maximum gross vehicle or combination weight shall be one hundred five thousand five hundred (105,500) pounds, provided that maximum gross vehicle or combination weight on United States federal interstate and defense highways of this state shall not exceed eighty thousand (80,000) pounds, except as permitted under the provisions of section 49-1004 , Idaho Code.

1. (1) The total gross weight imposed on the highway by any group of consecutive axles shall be determined by the following formula:

   1. (a) A public highway agency may limit the application of the weights authorized in this section as to certain highways within its jurisdiction which it determines have limited structural capacity of pavements, bridges, or other appurtenances. In designating such highways, it may specify a minimum wheelbase for combinations to be operated thereon. It may also designate specific highways or portions on which operation of a combination of vehicles with seven (7) through thirteen (13) axles will be subject to specified lesser allowable gross weights.
   2. (b) Notwithstanding the figures shown in the table in this subsection (1), two (2) consecutive sets of tandem axles may carry a gross load of thirty-four thousand (34,000) pounds each, providing the overall distance between the first and last axles of such consecutive sets of tandem axles is thirty-six (36) feet or more.
   3. (c) Vehicles may operate with reducible loads at gross weights greater than one hundred five thousand five hundred (105,500) pounds but not exceeding one hundred twenty-nine thousand (129,000) pounds on noninterstate highways in accordance with the provisions of section 49-1004, Idaho Code, provided such vehicles are in compliance with the weight formula specified in this subsection (1) of this section, have registered and have paid the registration fees as specified in section 49-434, Idaho Code, and are in compliance with the length restrictions set forth in section 49-1010(7), Idaho Code.

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

   Where W is the maximum weight in pounds (to the nearest 500 pounds) carried on any group of two (2) or more consecutive axles. L is the distance in feet between the extremes of any group of two (2) or more consecutive axles, and N is the number of axles under consideration.

   The formula is modified as illustrated in the following table:

   Distance in feet between the extremes of any group of 2 or more consecutiveMaximum load in pounds carried on any group of 2 or more consecutive axles axles2 axles3 axles4 axles5 axles6 axles7 axles8 axles9 axles10 axles11 axles12 axles13 axles 4 34,000 5 34,000 WHEN NO ALLOWABLE WEIGHT IS 6 34,000 LISTED FOR ANY AXLE SPACING, 7 34,000 APPLY THE ALLOWABLE WEIGHT 8 34,000 AS LISTED IN THE FIRST COLUMN 8+ 38,000 42,000 TO THE LEFT 9 39,000 42,500 10 40,000 43,500 11 44,000 12 45,000 50,000 13 45,500 50,500 14 46,500 51,500 15 47,000 52,000 16 48,000 52,500 58,000 17 48,500 53,500 58,500 18 49,500 54,000 59,000 19 50,000 54,500 60,000 20 51,000 55,500 60,500 66,000 21 51,500 56,000 61,000 66,500 22 52,500 56,500 61,500 67,000 23 53,000 57,500 62,500 68,000 24 54,000 58,000 63,000 68,500 74,000 25 54,500 58,500 63,500 69,000 74,500 26 55,500 59,500 64,000 69,500 75,000 27 56,000 60,000 65,000 70,000 75,500 28 57,000 60,500 65,500 71,000 76,500 82,000 29 57,500 61,500 66,000 71,500 77,000 82,500 30 58,500 62,000 66,500 72,000 77,500 83,000 31 59,000 62,500 67,500 72,500 78,000 83,500 32 60,000 63,500 68,000 73,000 78,500 84,500 90,000 33 64,000 68,500 74,000 79,000 85,000 90,500 34 64,500 69,000 74,500 80,000 85,500 91,000 35 65,500 70,000 75,000 80,500 86,000 91,500 36 66,000 70,500 75,500 81,000 86,500 92,000 98,000 37 66,500 71,000 76,000 81,500 87,000 93,000 98,500 38 67,500 71,500 77,000 82,000 87,500 93,500 99,000 39 68,000 72,500 77,500 82,500 88,500 94,000 99,500 40 68,500 73,000 78,000 83,500 89,000 94,500 100,000 106,000 41 69,500 73,500 78,500 84,000 89,500 95,000 100,500 106,500 42 70,000 74,000 79,000 84,500 90,000 95,500 101,000 107,000 43 70,500 75,000 80,000 85,000 90,500 96,000 102,000 107,500 44 71,500 75,500 80,500 85,500 91,000 96,500 102,500 108,000 114,000 45 72,000 76,000 81,000 86,000 91,500 97,500 103,000 108,500 114,500 46 72,500 76,500 81,500 87,000 92,500 98,000 103,500 109,000 115,000 47 73,500 77,500 82,000 87,500 93,000 98,500 104,000 110,000 115,500 48 74,000 78,000 83,000 88,000 93,500 99,000 104,500 110,500 116,000 122,000 49 74,500 78,500 83,500 88,500 94,000 99,500 105,000 111,000 116,500 122,500 50 75,500 79,000 84,000 89,000 94,500 100,000 105,500 111,500 117,000 123,000 51 76,000 80,000 84,500 89,500 95,000 100,500 106,000 112,000 118,000 123,500 52 76,500 80,500 85,000 90,500 95,500 101,000 107,000 112,500 118,500 124,000 53 77,500 81,000 86,000 91,000 96,500 102,000 107,500 113,000 119,000 124,500 54 78,000 81,500 86,500 91,500 97,000 102,500 108,000 113,500 119,500 125,000 55 78,500 82,500 87,000 92,000 97,500 103,000 108,500 114,000 120,000 125,500 56 79,500 83,000 87,500 92,500 98,000 103,500 109,000 115,000 120,500 126,000 57 80,000 83,500 88,000 93,000 98,500 104,000 109,500 115,500 121,000 127,000 58 84,000 89,000 94,000 99,000 104,500 110,000 116,000 121,500 127,500 59 85,000 89,500 94,500 99,500 105,000 110,500 116,500 122,000 128,000 60 85,500 90,000 95,000 100,500 105,500 111,000 117,000 122,500 128,500 61 86,000 90,500 95,500 101,000 106,000 112,000 117,500 123,000 129,000 62 87,000 91,000 96,000 101,500 107,000 112,500 118,000 124,000 63 87,500 92,000 96,500 102,000 107,500 113,000 118,500 124,500 64 88,000 92,500 97,500 102,500 108,000 113,500 119,000 125,000 65 88,500 93,000 98,000 103,000 108,500 114,000 119,500 125,500 66 89,500 93,500 98,500 103,500 109,000 114,500 120,000 126,000 67 90,000 94,000 99,000 104,500 109,500 115,000 121,000 126,500 68 90,500 95,000 99,500 105,000 110,000 115,500 121,500 127,000 69 91,000 95,500 100,000 105,500 111,000 116,000 122,000 127,500 70 92,000 96,000 101,000 106,000 111,500 117,000 122,500 128,000 71 92,500 96,500 101,500 106,500 112,000 117,500 123,000 128,500 72 93,000 97,000 102,000 107,000 112,500 118,000 123,500 129,000 73 93,500 98,000 102,500 107,500 113,000 118,500 124,000 74 94,500 98,500 103,000 108,000 113,500 119,000 124,500 75 95,000 99,000 103,500 109,000 114,000 119,500 125,000 76 95,500 99,500 104,500 109,500 114,500 120,000 126,000 77 96,000 100,000 105,000 110,000 115,000 120,500 126,500 78 97,000 101,000 105,500 110,500 116,000 121,000 127,000 79 97,500 101,500 106,000 111,000 116,500 122,000 127,500 80 98,000 102,000 106,500 111,500 117,000 122,500 128,000 81 98,500 102,500 107,000 112,000 117,500 123,000 128,500 82 99,000 103,000 108,000 113,000 118,000 123,500 129,000 83 100,000 104,000 108,500 113,500 118,500 124,000 84 104,500 109,000 114,000 119,000 124,500 85 105,000 109,500 114,500 120,000 125,000 86 105,500 110,000 115,000 120,500 125,500 87 106,000 111,000 115,500 121,000 126,000 88 107,000 111,500 116,000 121,500 127,000 89 107,500 112,000 117,000 122,000 127,500 90 108,000 112,500 117,500 122,500 128,000 91 108,500 113,000 118,000 123,000 128,500 92 109,000 113,500 118,500 123,500 129,000 93 110,000 114,000 119,000 124,000 94 110,500 115,000 119,500 125,000 95 111,000 115,500 120,000 125,500 96 111,500 116,000 121,000 126,000 97 112,000 116,500 121,500 126,500 98 113,000 117,000 122,000 127,000 99 113,500 118,000 122,500 127,500 100 114,000 118,500 123,000 128,000 101 114,500 119,000 123,500 129,000

2. (2) The weight limitations set forth in the table in subsection (1) of this section shall not apply to any vehicle, or combination of vehicles when a greater allowed weight in pounds would be permitted such vehicles under the table provided in this subsection, except that with regard to transportation on the United States federal interstate and defense highways of this state, the following table of allowable weights shall apply only to vehicles engaged in the transportation of logs, pulp wood, stull, rough lumber, poles or piling; or to any such vehicle engaged in the transportation of ores, concentrates, sand and gravel and aggregates thereof, in bulk; or to any such vehicle engaged in the transportation of agricultural commodities, including livestock:

   Distance in feet betweenAllowed Load in Pounds the extremes of any groupVehicles withVehicles with of 2 or more consecutiveThree or FourFive or more axlesaxlesaxles 3 through 12 37,800 37,800 13 56,470 56,470 14 57,940 57,940 15 59,400 59,400 16 60,610 60,610 17 61,820 61,820 18 63,140 63,140 19 64,350 64,350 20 65,450 65,450 21 66,000 66,330 22 66,000 67,250 23 66,000 67,880 24 66,000 68,510 25 66,000 69,150 26 66,000 69,770 27 66,000 70,400 28 66,000 70,950 29 66,000 71,500 30 66,000 72,050 31 72,600 32 73,150 33 73,700 34 74,250 35 74,800 36 75,350 37 75,900 38 76,450 39 77,000 40 77,550 41 78,100 42 78,650 43 and over 79,000

   The weight allowances provided in this subsection do not apply if the total gross weight of a vehicle or combination of vehicles is intended to exceed seventy-nine thousand (79,000) pounds as declared by the operator. When the provisions of this subsection are applicable to a vehicle or combination of vehicles, it shall be a violation of the provisions of this subsection if that vehicle or combination of vehicles exceeds the weights specified in this table.

3. (3) In determining the gross weight of a vehicle or the gross weight of any two (2) or more consecutive axles under subsection (1) or (2) or (9) of this section, the total gross weight of the vehicle or combination of vehicles or the gross weight of any two (2) or more consecutive axles shall be the sum of the axle weights.

   1. (a) The sum of the axle weights exceeds what is allowable under the provisions of subsection (1) or (2) or (9) of this section;
   2. (b) The scale involved in the weighing was at the time of weighing calibrated in conformity with and met the accuracy requirements of the standards for the enforcement of traffic and highway laws as set forth in the latest edition of handbook 44 of the national institute of standards and technology;
   3. (c) Weights of individual axles or axles within a commonly suspended group of axles supported by a mechanical system designed to distribute equal wheel loads to individual axles in the group were utilized only to determine gross weights of that group of axles, and that any further evaluation of gross weights of combinations of axles considered only the accumulated gross weight of each such commonly suspended group of axles.

   For the purposes of this chapter the gross weight of a vehicle or the gross weight of any two (2) or more consecutive axles may be determined by accumulatively adding the separate weights of individual axles and tandem axles or groups of axles to determine gross weight. The results of any weighing at a temporary or permanent port of entry and the records relating to the calibration and accuracy of any scale at a temporary or permanent port of entry shall be admissible in any proceeding in this state. In order to prove a violation of the provisions of this section the state must show that:

4. (4) In applying the weight limitations imposed in this section, a vehicle or combination of vehicles must comply exclusively with the weight limitations in either subsection (1) or (2) or (9) of this section.
5. (5) In applying the weight limitations imposed in this section, the distance between axles shall be measured to the nearest even foot. When a fraction is exactly one-half (1/2) foot the next larger whole number shall be used.
6. (6) The limitations imposed in this section are in addition and supplemental to all other laws imposing limitations upon the size and weight of vehicles. Further, single axles within groups of axles are subject to the provisions and limitations of this chapter. Single axles within groups of axles may be weighed and evaluated separately.
7. (7) Notwithstanding the other provisions of this chapter, no vehicle, motor vehicle, trailer and/or semitrailer, or combination thereof, may be operated on the public highways of the state under loads which would result in the withholding of funds by operation of controlling federal law as provided in the Federal Aid Highway Act of 1956, as amended.

8. (8) Except as provided herein, no vehicle or combination of vehicles may proceed past the place of weighing at temporary or permanent ports of entry or checking stations when: the weight of a single axle exceeds the maximum limitations set forth herein by two thousand (2,000) pounds or more; the weight of a combination of axles, or gross vehicle weight exceeds the maximum allowable weight as set forth herein by seven percent (7%) or more. Vehicles or combinations of vehicles which exceed the weight limitations set forth herein shall be required to be brought into compliance with applicable weight limitations contained within this subsection at the place of weighing prior to continuing, except those vehicles or combinations of vehicles which are transporting loads which, in the determination of the board or other proper authorities in charge of or having jurisdiction over a highway, are deemed unsafe or impractical to bring into compliance at the place of weighing, and except those vehicles which do not exceed fifteen percent (15%) over maximum axle and axle group weights set forth in this section. Vehicles or combinations of vehicles transporting loads in this latter category shall obtain a travel authorization to the nearest place of safe unloading, load adjustment or other means of legalization.

   1. (a) Neither the state of Idaho or its employees, nor any authority and its employees in charge of or having jurisdiction over a highway, shall be held liable for personal injury or property damage resulting from the requirements of section 49-1001(8), Idaho Code.
   2. (b) The fee for a travel authorization as set forth above shall be fifty dollars ($50.00) and shall be on a form prescribed by the board or other proper authorities, and shall not be construed as contributing to a reduction in the penalties prescribed in section 49-1013, Idaho Code.
   3. (c) The board or other proper authorities in charge of or having jurisdiction over a highway shall adopt and enforce administrative rules as may be necessary to carry out the provisions of this section.

9. (9) For vehicles on all highways except the United States federal interstate and defense highways of this state, the following table shall apply:

   Distance in feet betweenAllowed Load in Pounds the extremes of any groupVehicles withVehicles with of 2 or more consecutiveThree or FourFive or more axlesaxlesaxles 3 through 12 37,800 37,800 13 56,470 56,470 14 57,940 57,940 15 59,400 59,400 16 60,610 60,610 17 61,820 61,820 18 63,140 63,140 19 64,350 64,350 20 65,450 65,450 21 66,000 66,330 22 66,000 67,250 23 66,000 67,880 24 66,000 68,510 25 66,000 69,150 26 66,000 69,770 27 66,000 70,400 28 66,000 70,950 29 66,000 71,500 30 66,000 72,050 31 72,600 32 73,150 33 73,700 34 74,250 35 74,800 36 75,350 37 75,900 38 76,450 39 77,000 40 77,550 41 78,100 42 78,650 43 and over 80,000

   The weight allowances provided in this subsection do not apply if the total gross weight of a vehicle or combination of vehicles is intended to exceed eighty thousand (80,000) pounds as declared by the operator. When the provisions of this subsection are applicable to a vehicle or combination of vehicles, it shall be a violation of the provisions of this subsection if that vehicle or combination of vehicles exceeds the weights specified in this table.

10. (10) Variable load suspension axles shall meet the following criteria in order to be included in the computation of gross vehicle or axle weight limits for vehicles under the provisions of this section:

    1. (a) The deployment control switch for such axles may be located inside of the driver’s compartment but the pressure regulator valve for the operation of pressure on the pavement shall be located outside of and inaccessible to the driver’s compartment.
    2. (b) The manufacturer’s gross axle weight rating of each such axle must not be less than the actual loading of the axle.
    3. (c) All variable load suspension axles shall be designed to be self-steering; provided however, variable load suspension axles that are within sixty (60) inches of a drive axle or are within sixty (60) inches of a trailer axle, need not be self-steering.
    4. (d) The manufacturer’s gross tire weight rating of each tire must not be less than the actual loading of the tire.
    5. (e) Variable load suspension axles must be fully deployed or fully raised. For applicable definitions, see sections 49-117 and 49-123, Idaho Code.
11. (11) Any person who operates a motor vehicle with a variable load suspension axle in violation of the provisions of this section shall be subject to the penalties provided in section 49-1013, Idaho Code.

[49-1001, added 1988, ch. 265, sec. 272, p. 715; am. 1991, ch. 226, sec. 1, p. 538; am. 1993, ch. 273, sec. 4, p. 921; am. 1993, ch. 334, sec. 3, p. 1238; am. 1993, ch. 345, sec. 1, p. 1284; am. 1993, ch. 371, sec. 1, p. 1334; am. 1993, ch. 376, sec. 2, p. 1380; am. 1994, ch. 321, sec. 4, p. 1030; am. 1995, ch. 72, sec. 1, p. 183; am. 1995, ch. 122, sec. 3, p. 532; am. 1998, ch. 158, sec. 2, p. 535; am. 1998, ch. 189, sec. 1, p. 684; am. 2000, ch. 418, sec. 15, p. 1352; am. 2007, ch. 65, sec. 1, p. 159; am. 2015, ch. 208, sec. 9, p. 648.]