Let me repeat what I wrote on my blog (especially #2 and #3, in this case):
And if you’re about to tell me you don’t believe motorcyclists should be able to lane-split, let me ask you to answer three questions honestly:
1.Are you hearing “lane-splitting” and imagining a rider doing a 60 mph stand-up wheelie between rows of stopped traffic? A California study showed that when lane-splitting is done responsibly, within the guidelines recommended by the California Highway Patrol, it is not unsafe. Nobody is suggesting that irresponsible riding should be legalized. Just sensible lane-splitting, like what happens every day, all over the world.
2.Are you speaking from experience and knowledge or pure supposition? Have you ridden where lane-splitting is legal and accepted, so drivers know to expect it? If not, how do you know it’s a bad idea?
3.Do you realize that making lane-splitting legal does not require you to do it? If you prefer sitting in traffic, you can continue to do so. Why deny the rest of us the improved ability to get where we’re going and contribute less to traffic congestion?
2). I have lived and ridden in CA
3). I know.
As a motorcyclist, I'm OK with it being legal, I may even do it but it'll be my choice as to when. As a cager, I'm against it because it won't be my choice as to when or with whom I'll be sharing a lane. I like having a whole lane, it gives me a few feet of emergency space to the sides if I need to avoid something in the road or an opening car door or if I need to adjust lane position to better see. Lane position is a valuable tool for safe driving. If a rider chooses to give up that space, that's their business, but to take that space away from someone else is a different thing and that's the problem I have with it.
Lets partition for a law that says cars can lane split with motorcycles. How would that work for you? They can just drive up beside you, take 3/4 of your lane, whenever they want and it's perfectly fine. Too bad for you if you can't avoid the gravel or oil or a 2X4 laying in the road because a cager decided it was a good time to use most of your lane to pass.
As soon as you can come up with a valid reason this would benefit 95% of the road users then it's all good. (and no, easing traffic congestion doesn't get it, we both know that's BS)