On September 16th, 2014, a new law goes into effect here in California, to protect bicyclists. This "3 Feet For Safety" law specifies that motorists must keep a distance of 3' from a bicyclist, when passing the bicyclist going in the same direction. If you can not safely pass the bicyclist while leaving a distance of 3', then the law requires you wait to pass, until it is safe to do so.
To read more about this and other similar laws, please refer to the following vehicle code sections:
21760(b) VC - Unsafe Passing of Bicyclist
21760(c) VC - Unsafe Passing Within 3' Of Bicyclist
21760(d) VC - Unsafe Speed While Passing Bicyclist
You can view these laws here.
As you can tell in the photo above, 3' is longer than we all think it is. Keep this in mind the next time you see a bicyclist on the roadway.