21202.  (a) Any person operating a bicycle upon a roadway at a speed
less than the normal speed of traffic moving in the same direction
at that time shall ride as close as practicable to the right-hand
curb or edge of the roadway except under any of the following
situations:
   (1) When overtaking and passing another bicycle or vehicle
proceeding in the same direction.
   (2) When preparing for a left turn at an intersection or into a
private road or driveway.
   (3) When reasonably necessary to avoid conditions (including, but
not limited to, fixed or moving objects, vehicles, bicycles,
pedestrians, animals, surface hazards, or substandard width lanes)
that make it unsafe to continue along the right-hand curb or edge,
subject to the provisions of Section 21656.  For purposes of this
section, a "substandard width lane" is a lane that is too narrow for
a bicycle and a vehicle to travel safely side by side within the
lane.
   (4) When approaching a place where a right turn is authorized.
   (b) Any person operating a bicycle upon a roadway of a highway,
which highway carries traffic in one direction only and has two or
more marked traffic lanes, may ride as near the left-hand curb or
edge of  that roadway as practicable.