§ 1164. Signals by hand and arm or signal lamps. (a) Any stop or turn
signal when required herein shall be given either by means of the hand
and arm or by signal lamps, except as otherwise provided in subsection
(b).

(b) Any motor vehicle in use on a highway shall be equipped with, and
required signal shall be given by, signal lamps when the distance from
the center of the top of the steering post to the left outside limit of
the body, cab, or load of such motor vehicle exceeds twenty-four inches,
or when the distance from the center of the top of the steering post to
the rear limit of the body or load thereof exceeds fourteen feet. The
latter measurement shall apply to any single vehicle, also to any
combination of vehicles. On a combination of vehicles, the rear signal
lamps shall be at the rear of the last vehicle in the combination. The
provisions of this subdivision shall not apply to a vehicle, alone or in
combination with other vehicles or implements, if such vehicle is used
solely for agricultural purposes, and is not designed and intended
primarily for use on the highway, or to fire vehicles, or to special
purpose commercial motor vehicles registered under schedule F of
subdivision seven of section four hundred one of this chapter.