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:
   I. Left turn--Hand and arm extended horizontally.
   II. Right turn--Hand and arm extended upward.
   III. Stop or decrease speed--Hand and arm extended downward.
Source. 1948, 232:1, par. 18-c. RSA 263:26. 1963, 330:1. RSA 262-A:44. 1981, 146:1, eff. Jan. 1, 1982.