Hawaii Revised Statutes Division 1. Government § 291C-84

(a) No person shall turn a vehicle at an intersection unless the vehicle is in proper position upon the roadway as required in section 291C-81, or turn a vehicle to enter a private road or driveway, or otherwise turn a vehicle from a direct course or move right or left upon a roadway unless and until such movement can be made with reasonable safety. No person shall so turn any vehicle without giving an appropriate signal in the manner hereinafter provided.

(b) A signal of intention to turn right or left when required shall be given continuously during not less than the last one hundred feet traveled by the vehicle before turning; provided that for a bicycle or moped, such signal shall be given continuously during not less than the last one hundred feet traveled by the bicycle or moped before turning, and shall be given when the bicycle or moped is stopped waiting to turn; and further provided that a signal by hand and arm need not be given continuously by the driver of a bicycle or moped if the hand is needed in the braking, control, or operation of the bicycle or moped.

(c) No person shall stop or suddenly decrease the speed of a vehicle without first giving an appropriate signal in the manner provided herein to the driver of any vehicle immediately to the rear when there is opportunity to give such signal.

(d) The signals provided for in section 291C-85(b) shall be used to indicate an intention to turn, change lanes, or start from a parked position and shall not be flashed on one side only on a parked or disabled vehicle, or flashed as a courtesy or “do pass” signal to operators of other vehicles approaching from the rear.