75 Pa.C.S. § 3335: Signals by hand and arm or signal lamps.

(a) General rule.--Any stop or turn signal shall be given either by means of the hand and arm or by signal lamps, except as otherwise provided in subsection (b).

(b) Required signals by signal lamps.--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 the motor vehicle exceeds 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 exceeds 14 feet. The latter measurement shall apply to any single vehicle and to any combination of vehicles.

(c) Exception.--This section does not apply to a motor vehicle registered as an antique or classic vehicle which was not originally equipped with signal lamps.