The turnpikes, as established by RSA 237, and the approved national system of interstate and defense highways, shall be a part of the primary state highway system.
N.H. Rev. Stat. Ann. § 229:3
Turnpikes and System of Interstate and Defense Highways
Source
Official source: New Hampshire General Court. Reproduced from public-domain New Hampshire statutes; confirm against the official source for the current text. Not legal advice.