California become the first state in the nation to pass a bill to formalize the practice of lane splitting, and establishing lane-splitting guidelines for motorcyclists

http://www.latimes.com/politics/essential/la-pol-sac-essential-politics-updates-california-to-establish-lane-splitting-1470328822-htmlstory.html

I'd like to know why they can't use the shoulder instead. Seems to me that would be safer than going between cars who may change lanes without warning