2023 Idaho Code › Title 49 - MOTOR VEHICLES › Chapter 10 - WEIGHT, SPEED AND TIRE REGULATIONS › Section 49-1001 - ALLOWABLE GROSS LOADS.

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.]