2023 New Hampshire Revised Statutes › Title XXI - Motor Vehicles › Chapter 266 - Equipment of Vehicles › Section 266:18 - Weight on Interstate and Defense Highway System.

266:18 Weight on Interstate and Defense Highway System. –
The driving on the interstate and defense highway system of this state of any vehicle or combination of vehicles exceeding the limitations of this section is hereby prohibited.
I. Maximum tire and axle gross weights allowable:
(a) The manufacturer's load rating for the tires.
(b) When being driven with a gross weight in excess of 73,280 pounds:
(1) 20,000 pounds per axle on axles more than 8 feet apart;
(2) 17,000 pounds per axle on axles not more than 8 feet apart;
(c) When being driven with a gross weight not in excess of 73,280 pounds:
(1) 22,400 pounds per axle on 3-axle single unit vehicles and on all other vehicles with axles 10 feet or more apart, including combination vehicles;
(2) 18,000 pounds per axle on axles of vehicles less than 10 feet apart, except 3-axle single unit vehicles.
(d) Two axles less than 40 inches apart shall be considered as a single axle unit.
II. Maximum allowable vehicle gross weights:
(a) For 2-axle vehicles, 33,400 pounds.
(b) For single unit 3-axle vehicles, 47,500 pounds, or a gross weight not in excess of that produced by application of the weight formula as defined in subparagraph (h), whichever is greater, as shown in table III.
(c) For single unit 4-axle vehicles, provided that such vehicles shall have drive on 2 rear axles, and the tridem may contain not more than one retractable axle and, if not factory installed and load equalizing, must provide a system of load equalization by hydraulic, pneumatic, or mechanical means, and be equipped with brakes:
(1) 47,500 pounds, or a gross weight not in excess of that produced by application of the weight formula as defined in subparagraph (h), whichever is the greater; or
(2) If a heavy duty recovery vehicle, 75,000 pounds, or a gross weight not in excess of that produced by application of the weight formula as defined in subparagraph (h), whichever is the greater.
(d) For a single unit 5-axle heavy duty recovery vehicle, 80,000 pounds, or a gross weight not in excess of that produced by application of the weight formula as defined in subparagraph (h), whichever is the greater. Such vehicles shall have drive on 2 rear axles, and the tridem may contain not more than one retractable axle and, if not factory installed and load equalizing, must provide a system of load equalization by hydraulic, pneumatic, or mechanical means, and be equipped with brakes.
(e) For a combination of truck-tractor and semi-trailer equipped with 3 axles, the gross weight shall not exceed that set forth in table I as follows:
Table I.
Distance Between
Extreme Axles in Feet
Maximum Gross
Weight in Pounds
25
54,500
26
55,500
27
56,000
28
57,000
29
57,500
30
58,500
31
59,000
32
60,000
Further provided that the maximum tire and axle gross weights as provided in paragraph I shall apply and the maximum load in pounds carried on any group of 2 or more consecutive axles shall not exceed that produced by application of the weight formula as defined in subparagraph (h).
(f) For a combination of truck-tractor and semi-trailer equipped with 4 axles, the gross weight shall not exceed that set forth in table II as follows:
Table II.
Distance Between
Extreme Axles in Feet
Maximum Gross
Weight in Pounds
28
60,500
29
61,500
30
62,000
31
62,500
32
63,500
33
64,000
34
64,500
35
65,500
36
66,000
37
66,500
38
67,500
39
68,000
Further provided that the maximum tire and axle gross weights as provided in paragraph I shall apply, and the maximum load in pounds carried on any group of 2 or more consecutive axles shall not exceed that produced by application of the weight formula as defined in subparagraph (h).
(g) For a combination of truck-tractor and single semi-trailer with 5 or more axles with gross weight not in excess of 73,280 pounds, the weight on any single axle shall not exceed 22,400 pounds and the weight on any tandem axle shall not exceed 36,000 pounds.
(h) For a combination of truck-tractor and single semi-trailer equipped with 5 or more axles with a gross weight in excess of 73,280 pounds or a combination of truck-tractor and more than one trailing unit, the total gross weight shall not exceed 80,000 pounds including all law enforcement tolerances, and the overall gross weight on a group of 2 or more consecutive axles shall not exceed that produced by application of the following formula, known as the weight formula:
W = 500
{
LN
——
N − 1
+ 12N + 36
}
(In which W equals overall gross weight on any group of 2 or more consecutive axles to the nearest 500 pounds; L equals the distance measured to the nearest foot between the extreme of any group of 2 or more consecutive axles; and N equals the number of axles in the group under consideration.) Except that 2 consecutive sets of tandem axles may carry a gross load of 34,000 pounds each, provided the overall distance between the first and last axles of such consecutive sets of tandem axles is 36 feet or more and provided that such gross weight shall not exceed 80,000 pounds, including all law enforcement tolerances.
W = 500
{
LN
——
N − 1
+ 12N + 36
}
when expressed in tabular form results in maximum allowable load in pounds carried on any group of 2 or more consecutive axles as follows in table III.
Table III.
Distance
*
2 axles
3 axles
4 axles
5 axles
6 axles
7 axles
4
34,000
5
34,000
6
34,000
7
34,000
8 and less
34,000
34,000
more than 8
38,000
42,000
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
29
57,500
61,500
66,000
71,500
77,000
30
58,500
62,000
66,500
72,000
77,500
31
59,000
62,500
67,500
72,500
78,000
32
60,000
63,500
68,000
73,000
78,500
33
64,000
68,500
74,000
79,000
34
64,500
69,000
74,500
80,000
35
65,500
70,000
75,000
**
36
66,000
70,500
75,500
**
37
66,500
71,000
76,000
**
38
67,500
71,500
77,000
39
68,000
72,500
77,500
40
68,500
73,000
78,000
41
69,500
73,500
78,500
42
70,000
74,000
79,000
43
70,500
75,000
80,000
44
71,500
75,500
45
72,000
76,000
46
72,500
76,500
47
73,500
77,500
48
74,000
78,000
49
74,500
78,500
50
75,500
79,000
51
76,000
80,000
52
76,500
53
77,500
54
78,000
55
78,500
56
79,500
57
80,000
*
Distance in feet between the extremes of any group of 2 or more consecutive axles.
**
Distance in feet between the extremes of 4 axles. (2 sets of 2 axles) 68,000 gross weight exception. The permissible loads are computed to the nearest 500 pounds.
(i) The following loaded vehicles shall not be driven over H15-44 bridges:
(1) A combination vehicle equipped with 5 axles in the configuration of 3-axle truck-tractor and 2-axle semi-trailer with wheel base less than 38 feet or 2-axle truck-tractor with 1-axle semi-trailer and 2-axle full trailer with wheel base less than 45 feet.
(2) A loaded single unit vehicle with full trailer equipped with axles with wheel base less than 45 feet.
(3) Vehicles with 7, 8, or 9 axles.
(j) Coupled vehicles consisting of a truck together with a trailer attached to the truck by a pintle hook or similar coupling device with adequate breakaway protection as provided in RSA 266:63 may be driven, provided the total combined gross weight of the vehicles does not exceed 80,000 pounds and provided that each unit of the coupled vehicles shall be limited to the maximum permissible axle weights and gross weights of the individual units, and further provided that the weight of 2 or more consecutive axles of the coupled vehicle shall not be in excess of that produced by application of the weight formula as defined in subparagraph (h) and shall be limited to a total combined gross weight not in excess of 80,000 pounds, a single axle limit of 20,000 pounds and a tandem axle limit of 34,000 pounds.
III. Notwithstanding paragraphs I and II, for as long as exemptions exist in 23 U.S.C. section 127 that allow maximum gross weights of up to 99,000 pounds on interstate routes 89, 93, and 95 of the interstate and defense highway system, the provisions of RSA 266:18-a regarding weight on the non-interstate and general highway system shall also apply to vehicles or combination vehicles while being operated on any sections of interstate routes 89, 93, or 95 not posted by the commissioner of transportation for lower weights. Such vehicles shall not exceed the weight limits in paragraphs I and II unless they have been certified pursuant to RSA 266:18-d for the higher weights and paid the required fee the same as vehicles operating on the non-interstate highways as provided in RSA 266:18-d.
Source.
1921, 119:25. PL 103:22. 1927, 77:1. 1929, 33:1. 1933, 157:1. 1935, 133:1. 1937, 82:1. 1939, 131:1. 1941, 169:1. RL 119:37. 1947, 11:1. 1949, 104:1. 1950, 11:1, 2. 1951, 20:11. RSA 263:61. 1955, 230:1; 310:2. 1963, 189:1, 3; 202:1. 1973, 468:2. 1977, 487:1, 2. 1979, 219:1; 220:2; 239:1; 358:12. 1981, 55:1; 146:1. 1983, 434:15. 1986, 121:2. 1987, 404:20. 2005, 203:9, eff. July 1, 2005. 2018, 74:2, eff. July 24, 2018.