2015 New Hampshire Revised Statutes
Title XXI - MOTOR VEHICLES
Chapter 266 - EQUIPMENT OF VEHICLES
Section 266:18-a - Weight on Non-Interstate and General Highway System.

    266:18-a Weight on Non-Interstate and General Highway System. – The driving on ways of this state, other than on the interstate and defense highway system as provided by RSA 266:18, of any vehicle or combination of vehicles exceeding the limitations of this section is hereby prohibited; provided, however, that any police officer shall allow on any way other than the interstate and defense highway system a tolerance of 5 percent above said limitations.
    I. Maximum tire and axle gross weights allowable:
       (a) The manufacturer's load rating for the tires.
       (b) Two axles less than 40 inches apart shall be considered as a single axle unit.
       (c) When being driven on any way other than the interstate and defense highway system 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.
    II. Maximum allowable vehicle gross weight:
       (a) For 2-axle vehicles, 33,400 pounds.
       (b) For single unit 3-axle vehicles, 55,000 pounds, or a gross weight not in excess of that produced by application of the weight formula as defined in subparagraph (g), whichever is greater, as shown in table III in subparagraph (g).
       (c) For single unit 4-axle vehicles, 60,000 pounds, or a gross weight not in excess of that produced by application of the weight formula as defined in subparagraph (g), 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.
       (d) 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 Maximum Gross Weight
Extreme Axles in Feet 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 (g).
       (e) 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 Maximum Gross Weight
Extreme Axles in Feet 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 (g).
       (f) 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.
       (g) 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.

 LN 
The formula W = 500 ----- + 12N + 36
 N-1 

(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.

 LN 
The formula W = 500 ----- + 12N + 36
 N-1 

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 
 
FN* Distance in feet between the extremes of any group of 2 or more 
 consecutive axles. 
FN** 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.
       (h) 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.
       (i) 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 (g) 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.

Source. 1983, 434:16. 1986, 121:3; 136:7. 1987, 404:21. 2008, 39:1, eff. July 11, 2008.