Who:
"The bill, sponsored by Assembly member Bill Quirk (D-Hayward), passed Thursday with a 69-0 vote. It now goes to Gov. Jerry Brown for his signature."

What:
THE PEOPLE OF THE STATE OF CALIFORNIA DO ENACT AS FOLLOWS:

SECTION 1. Section 21658.1 is added to the Vehicle Code, to read:
21658.1. (a) For the purposes of this section, “lane splitting” means driving a motorcycle, as defined in Section 400, that has two wheels in contact with the ground, between rows of stopped or moving vehicles in the same lane, including on both divided and undivided streets, roads, or highways.
(b) The Department of the California Highway Patrol may develop educational guidelines relating to lane splitting in a manner that would ensure the safety of the motorcyclist and the drivers and passengers of the surrounding vehicles.
(c) In developing guidelines pursuant to this section, the department shall consult with agencies and organizations with an interest in road safety and motorcyclist behavior, including, but not limited to, all of the following:
(1) The Department of Motor Vehicles.
(2) The Department of Transportation.
(3) The Office of Traffic Safety.
(4) A motorcycle organization focused on motorcyclist safety.

Why:
"Technically, it has not been legal or illegal, falling in a gray area where it was treated as acceptable by law enforcement agencies. But when the CHP published safe strategies on the practice in 2015, a citizen complained that the agency should not be allowed to create public policy. In came in AB 51."

What it almost was:
"Quirk's original bill proposed that lane splitting could occur legally only when a motorcycle was moving no more than 15 miles per hour faster than the traffic around it, and it prohibited the practice at speeds above 50 mph."

Sources:
Direct link to the bill
Los Angeles Times article about the bill

TLDR: Lane splitting will be legal but subject to CHP's opinion if you are doing it correctly.

 

With all of the tobacco chewers and snuff dippers in Texas no one would want to split lanes here.

 

Lane splitting = death wish!

 

Man, Don't get the Cali boyz started again on lane splitting, let sleeping dogs lie.

 

If that was actually true, then why is lane splitting legal in pretty much the rest of the world?

There is a difference between riding between slow moving cars in a traffic jam and what Californians think what it means.

 

I was on the freeway yesterday in heavy traffic and as usual, a larger number then ever before of cars and trucks are pulling over making it easier for me to lane split. Is anyone else in CA experiencing this, that more cars and trucks are pulling over to make it easier to lane split?

 

Lane splitting = A major reason I enjoy my yearly rides to the Bay Area. It's safe, efficient and fun!

 

That is becoming the case more and more.

 

Lane splitting is the only way to get around in the Bay Area during rush hours. The traffic there is terrible.

 

Well, thats step one. I hope CHP comes up with reasonable guidelines.