Idaho Code § 49-810: Method of giving hand and arm signals.

All signals required to be given by hand and arm shall be given from the left side of the vehicle in the following manner, and the signals shall indicate the following:

(1) Left turn. – Hand and arm extended horizontally.

(2) Right turn. – Hand and arm extended upward. A person operating a bicycle may give a right turn signal by extending the right hand and arm horizontally and to the right side of the bicycle.

(3) Stop or decrease speed. Hand and arm extended downward.