N.H. Rev. Stat. Ann. § 266:11-b

The driving of triple trailer trucks on the ways of this state is prohibited. For the purposes of this section, "triple trailer" trucks shall mean the combination of a truck-tractor, as defined in RSA 259:116, which is used to draw 3 trailers as the term "trailer" is defined in RSA 259:113, where the resulting vehicle fails to conform to the provisions of RSA 266:11.