Appropriate hand signals, or signals by approved mechanical means, shall be given during the one hundred feet before stopping or turning at an intersection, or slowing down for parking, turning off the street or road, or any other purpose. When hand signals are used, a right turn shall be indicated by holding the arm upwards, a left turn by holding the hand and arm horizontally, and slowing or stopping by holding the arm downwards.
Haw. Code R. § 11-169-10