The HFL crew’s opinions and writing are sometimes subject to ridicule, but this is a good piece.
If you live in California and decide that lane splitting is simply too scary and dangerous for you, consider this: Attempting to occupy the space of a car with something barely larger than a bicycle simply doesn’t work. People will always be trying to change lanes into you, not seeing you in front of them and running you down. If you’ve ever ridden in traffic, you’ve undoubtedly encountered this before. I would put fear of being rear-ended or lane-changed into up there with having someone turn left in front of me.
Most places where splitting is legal or at least permitted, the general rule of thumb is that it’s only kosher to split through slow or stopped traffic. On the highway, slow might be 35-45mph. On a surface street, that might mean 15mph. Your relative speed to that traffic also matters. If you’re going 55mph through stopped traffic you’re a) a moron and b) likely to incur the wrath of the Highway Patrol, even if you’re not exceeding the speed limit. Again, this is all about judgement, but figure a 5-15mph speed difference. Don’t be an asshole and you should be alright.
Check out the whole article here.