N.H. Rev. Stat. § 21-L:12-b

I. Except as provided in paragraph III, the most current versions of the following design standards and manuals promulgated by the American Association of State Highway and Transportation Officials (AASHTO), inclusive of any amendments, revisions, interim revisions, or new editions promulgated by AASHTO are hereby adopted by reference, and the commissioner shall apply them to any project funded by state bridge aid or state highway aid as minimum standards in the state: (a) AASHTO load and resistance factor design for bridge design specifications; (b) AASHTO manual for condition evaluation of bridges; (c) AASHTO guide specifications for seismic isolation design; (d) AASHTO manual for condition evaluation and load resistance factor rating (LRFR) of highway bridges; (e) AASHTO standard specifications for structural supports for highway signs, luminaries, and traffic signals; (f) AASHTO policy on geometric design of highways and streets; and (g) AASHTO roadside design guide. II. At least 90 days prior to the adoption of any design standards or manuals under paragraph I the commissioner: (a) Shall publish notice of such standards or manuals in a statewide newspaper and at least one newspaper of general circulation in each county of the state. (b) Shall provide written notice of such standards or manuals to the associated general contractors of New Hampshire and other contractors with whom the department is doing business. (c) May, in appropriate situations, hold a public hearing. III. For modifications to an existing bridge, the commissioner may require load resistance factor design (LRFD) specifications from the most current version of the applicable AASHTO manual listed in paragraph I or the specifications that were used for the original design of the bridge.