If you needed a reason to keep headlights, tail lights, etc. in good working order, the NH Dept. of Safety website linked to below may give it to you. Among other things, the website lists cases in which problems with vehicle lighting were used as justification for a stop.
The administrative rules from the New Hampshire Department of Safety, Saf-C 3215 and 3216, give more detail on the type of lighting equipment each vehicle must have. Fog lamps on school buses (Saf-C 1313.09); how many fog lamps a vehicle may have (Saf-C 3215.05), and more detail about what color emergency lights can be and who can use them (Saf-C 3215.02) are just some of the topics covered in regulations.
Please remember that this guide is for information purposes only and is not comprehensive. It is intended as a starting point for research, to illustrate the various sources of the law, and to provide guidance in their use. NH Law About ... is not a substitute for the services of an attorney.