RSA 266:56: Windshield Wipers and Defrosters.

Every motor vehicle shall be equipped with a windshield wiper, or wipers so-called, for cleaning rain, ice, snow or other moisture from its windshield, and every motor vehicle manufactured after January 1, 1947, shall, in addition to such windshield wiper, be also equipped with a defroster, so-called, designed for melting snow and ice from the windshield. All such devices shall at all times be maintained in good working condition.