N.H. Rev. Stat. § 266:18-c — NH Code / Title XXI / Chapter 266 / Section 18-c
266:18-c General Weight Provisions.
Status: in_force

The following provisions shall apply to any vehicle covered by RSA 266:18, 18-a, or 18-b, regardless of the type of way or highway on which it is driven, except as otherwise specified: I. A vehicle or combination of vehicles equipped with any solid rubber tires shall not have weights more than 80 percent of those permitted; provided that no vehicle equipped with solid rubber tires which has at any point less than one inch of rubber above the top or beyond the flange or rim shall be driven upon any way. II. Motor vehicles or vehicles drawn by motor vehicles when equipped with metal or other hard tires shall not have weights more than 40 percent of those permitted. III. The provisions of RSA 266:18, 18-a, and 18-b shall not apply to vehicles used exclusively in the surfacing of ways of the state of New Hampshire, or subdivisions thereof; provided that the commodities of tar, asphalt, or the combination thereof shall not exceed 2,000 gallons on any 2-axle vehicle, or 4,000 gallons on any 3-axle vehicle. IV. A vehicle or combination of vehicles shall not be driven or moved over any bridge or other structure on any way if the weight of such vehicle, or combination of vehicles and load, is greater than the capacity of the structure as shown by a sign on the right side of or overhead on the structure. V. It shall be the duty of the commissioner of transportation to cause signs to be erected at both ends on the right side of or overhead on all bridges or other structures under his jurisdiction stating the capacity in tons of 2,000 pounds which the bridge or other structure will safely carry. As an alternative to posting signs with stated weight limits, the commissioner of transportation may, at his discretion, post standardized warning signs designating certain restricted bridges as caution crossing bridges, or as excluded bridges, and publish a list which designates all such bridges so conditioned at least annually. For all other bridges or other structures it shall be the duty of the authority having jurisdiction to place similar signs. The signing message for posting of weight limits for bridges and structures shall read as follows: WEIGHT LIMIT X TONS If the authority determines that a bridge or other structure may safely carry loads greater than this limit by vehicles with 3 or more axles, the signs shall read as follows: GROSS WEIGHT LIMIT X TONS OR Y% OF LEGAL LOADS "X" is the numerical value that equals the posted maximum legal gross weight limit for a 2-axle vehicle. "Y%" is the numerical value expressed as a percentage of the maximum legal gross weight limit of any single axle or tandem axle, and the combined gross weight limit of any 3-axle truck or any combination as noted in this section. Where no special permit loads are allowed, the signing message for posting shall read as follows: NO PERMIT LOAD LEGAL LOADS MAXIMUM Upon bridges or other structures of sufficient strength to carry safely the legal loads permissible by this section, no such signs shall be required. VI. A determination of the gross weight of vehicles under the tables as set forth in RSA 266:18, 18-a, and 18-b shall, in cases in which the distance between extreme axles is not in exact number of feet, be governed by the following: if the distance is 6 inches or less in excess of the number of feet stated in the table, the gross weight shall be based upon the number of feet stated in the table; if the distance is more than 6 inches in excess of the number of feet in the table, the gross weight shall be based upon the next higher number of feet. VII. Any vehicle subject to this subdivision that utilizes an auxiliary power or idle reduction technology unit in order to promote reduction of fuel use and emissions because of engine idling, may be allowed up to an additional 550 pounds in gross, axle, tandem, or bridge formula weight limits. To be eligible for this exception the driver of the vehicle must be able to prove by written certification the weight of the auxiliary power unit and by demonstration or certification that the idle reduction technology is fully functional at all times. Certification of the weight of the auxiliary power unit must be available to law enforcement officers if the vehicle is found in violation of applicable weight laws. The additional weight allowed may not exceed 550 pounds or the weight certified, whichever is less.