California's 3-foot buffer zone for cyclists takes effect today

[petronius]

2. As I read it, it seems to only apply to "overtaking"

A bicycle, but no word on whether the bike has to be there legally or not.

21760. (a) This section shall be known and may be cited as the
Three Feet for Safety Act.
(b) The driver of a motor vehicle overtaking and passing a bicycle
that is proceeding in the same direction on a highway shall pass in
compliance with the requirements of this article applicable to
overtaking and passing a vehicle, and shall do so at a safe distance
that does not interfere with the safe operation of the overtaken
bicycle, having due regard for the size and speed of the motor
vehicle and the bicycle, traffic conditions, weather, visibility, and
the surface and width of the highway.
(c) A driver of a motor vehicle shall not overtake or pass a
bicycle proceeding in the same direction on a highway at a distance
of less than three feet between any part of the motor vehicle and any
part of the bicycle or its operator.
(d) If the driver of a motor vehicle is unable to comply with
subdivision (c), due to traffic or roadway conditions, the driver
shall slow to a speed that is reasonable and prudent, and may pass
only when doing so would not endanger the safety of the operator of
the bicycle, taking into account the size and speed of the motor
vehicle and bicycle, traffic conditions, weather, visibility, and
surface and width of the highway.
(e) (1) A violation of subdivision (b), (c), or (d) is an
infraction punishable by a fine of thirty-five dollars ($35).
(2) If a collision occurs between a motor vehicle and a bicycle
causing bodily injury to the operator of the bicycle, and the driver
of the motor vehicle is found to be in violation of subdivision (b),
(c), or (d), a two-hundred-twenty-dollar ($220) fine shall be imposed
on that driver.
(f) This section shall become operative on September 16, 2014.

Section 'd' makes it sound like the old law still applies where 3' isn't possible, but I'll let someone else be the test of that...