(a) Any person operating a motor vehicle and making a turn or coming to a stop shall signal the turn or stop in accordance with this section.
(b) A signal for a turn or stop is made by fully extending the left arm as follows:
(1) Left turn - extend left arm horizontally.
(2) Right turn - extend left arm upward.
(3) Stop or decrease speed - extend left arm downward.
(c) A signal light or other device may be used in place of an arm signal prescribed in paragraph (b) of this section if it is visible and intelligible.