Whenever a stop or turn signal is required by s. 346.34, such signal may in any event be given by a signal lamp or lamps of a type meeting the specifications set forth in s. 347.15. Except as provided in s. 347.15 (3m), such signals also may be given by the hand and arm in lieu of or in addition to signals by signal lamp. When given by hand and arm, such signals, except signals by the operator of a bicycle, who may use either hand and arm, shall be given from the left side of the vehicle in the following manner and shall indicate as follows:

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

   (2)   Right turn – Hand and arm extended upward.

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