Join Date: Aug 2008
Location: Ikea Town, NorCal
The law is mute on lane sharing in that it doesn't allow it or disallow it. It's merely acceptable with one major caveat: it's at the officer's discretion to determine if you're engaged in an unsafe activity. There is no limit on how much faster than traffic you can be going. If traffic's crawling along at 35 you could, technically, go 70 (assuming that's the freeway's limit; it's 65 in much of the state), but by most standards that'd be unsafe and ticketable. I have done 25-35 between the HOV (carpool) lane and the #1 lane with both lanes stopped, while following a CHiP. The HOV-1 gap tends to be much larger.
I regularly split at freeway speeds to get myself into open spots away from other traffic. I also filter on city streets, particularly to and away from stoplights. I'd recommend you experiment with the latter first. If you do split lanes on the freeway, stay away from the HOV-1 and 1-2 gaps to begin with as you might find yourself with several guys stacked up behind you due to the relative experience levels; you don't need the extra worry factor. The size of the gap and the speed you're comfortable with will change as you become more comfortable splitting. I've unintentionally scared the ever-loving crap out of passengers in cages I've been driving by putting the car into a spot that they wouldn't have thought it would have gone (most often when making a right turn at a stoplight and filtering to the front to do so); I've been splitting for my entire driving career (first vehicle was a bike).
Keep in mind that while our awareness as motorcyclists is necessarily heightened (if it isn't, consider stopping riding), you really have to turn it up to split. Guy dropping coffee in his lap and jerking the wheel a tiny bit can turn a great day into an ugly one. A good amount of awareness (constant scanning, including other vehicles' mirrors to see if the car that's crowding the line is using his mirror [changing lanes] or is just completely oblivious to his lane position), covering the front brake, careful throttle control, and tending to stay in a higher gear than you normally would (to allow for increased engine braking and faster acceleration if you need it) are all good practices.
BTW, lane splitting, lane sharing, and filtering are all the same, though filtering tends to connote that traffic's stopped, at least Stateside.