(1) Any stop or turn signal when required shall be given either by means of hand and arm, or by signal lamps, except as otherwise provided in subsection (2) of this section.
(2) Any motor vehicle in use on a highway shall be equipped with, and the 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 the vehicle exceeds twenty-four (24) 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 (14) feet. The latter measurements shall apply not only to any single vehicle, but also to any combination of vehicles.