Any stop or turn signal when required herein shall be given either by means of the hand and arm or by a signal lamp or lamps or mechanical signal device, but when a vehicle is so constructed or loaded that hand and arm signal would not be visible both to the front and rear of such vehicle, then such signals must be given by such a lamp or lamps or signal device.
(W. Va. Code 17C-8-9) (Prior Code, § 339.09)