N.Y. Veh. & Traf. Law § 1237

§ 1237. Method of giving hand and arm signals by bicyclists. All\nsignals herein required to be given by bicyclists by hand and arm shall\nbe given in the following manner and such signals shall indicate as\nfollows:\n 1. Left turn. Left hand and arm extended horizontally.\n 2. Right turn. Left hand and arm extended upward or right hand and arm\nextended horizontally.\n 3. Stop or decrease speed. Left hand and arm extended downward.\n