N.H. Rev. Stat. Ann. § 266:27-a

Every motor vehicle and combination of vehicles except motorcycles, farm tractors and mopeds, shall have a parking brake system adequate to hold the vehicle or combination of vehicles on any grade on which it is driven under all conditions of loading on a surface free from snow, ice or loose material, and which shall comply with performance standards issued by the director by rule adopted pursuant to RSA 260:5.