All signals herein required given by hand and arm shall be given from the left side of the vehicle in the following manner and such signals shall indicate as follows:
(1) Left turn--hand and arm extended horizontally.
(2) Right turn--hand and arm extended upward, except bicyclists may signal using the right hand and arm extended horizontally from the right side of the bicycle.
(3) Stop or decrease speed--hand and arm extended downward.