TITLE 49

MOTOR VEHICLES

CHAPTER 10

WEIGHT, SPEED AND TIRE REGULATIONS

49-1001.  ALLOWABLE GROSS LOADS. 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)  The total gross weight imposed on the highway by any group of consecutive axles shall be determined by the following formula:

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 consecutive		Maximum load in pounds carried on any group of 2 or more consecutive axles
axles	2 axles	3 axles	4 axles	5 axles	6 axles	7 axles	8 axles	9 axles	10 axles	11 axles	12 axles	13 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

(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.

(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.

(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.

(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 between	Allowed Load in Pounds
the extremes of any group	Vehicles with	Vehicles with
of 2 or more consecutive	Three or Four	Five or more
axles	axles	axles
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)  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.

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:

(a)  The sum of the axle weights exceeds what is allowable under the provisions of subsection (1) or (2) or (9) of this section;

(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;

(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.

(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)  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)  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)  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)  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.

(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.

(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.

(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)  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 between	Allowed Load in Pounds
the extremes of any group	Vehicles with	Vehicles with
of 2 or more consecutive	Three or Four	Five or more
axles	axles	axles
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) 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:

(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.

(b)  The manufacturer’s gross axle weight rating of each such axle must not be less than the actual loading of the axle.

(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.

(d)  The manufacturer’s gross tire weight rating of each tire must not be less than the actual loading of the tire.

(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) 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.

History:

[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.]