While all other states prohibit lane-splitting, the Golden State does not. And though it isn't explicitly permitted, that may change soon. | Photo: Steven Vance /Flickr/ Creative Commons

It is morning on the freeway. Rush hour. Your sedan cruises along with the flow of traffic, hitting a whopping top speed of 15 miles per hour.

And then: vroooom!!

A motorcyclist zips by doing 40 mph, inches from your side view mirror.

The rider is partaking of the quasi-legal practice of lane-splitting, riding a motorcycle between cars in adjacent lanes. Though irritating or unnerving to many drivers, lane-splitting is not outlawed in California. While all other states prohibit lane-splitting, the Golden State does not. And though it isn't explicitly permitted, that may change soon.

AB 51 is a new bill that would make lane-splitting unequivocally legal, permissible when traffic is moving at 30 mph or less and when motorcyclists drive no more than 10 mph faster than nearby traffic.

A UC Berkeley study released last fall found that lane-splitting is no more perilous than riding a motorcycle in a marked lane except when motorcyclists drive 10 or more mph faster than the surrounding traffic.

Bill Quirk, the bill's author, told KCET that he wrote the proposal because of his "concern for traffic safety," and state agencies' "inability" to educate drivers after the Department of Motor Vehicles and the California Highway Patrol both removed lane-splitting safety guidelines from their materials last summer.

A fact sheet from the assemblymember's office offers another reason for why he feels the legislation is necessary: "There are many motorcyclists who lane split only in slow traffic conditions, however, many disregard speed limits and road conditions and lane split at unsafe speeds."

Not so fast, said Chuck Koro, an attorney who represents motorcyclists and called the proposal "problematic." He believes the law, if passed, will be difficult to enforce, partly because of the difficulty of determining the speed of surrounding traffic. Vehicles in different lanes may be traveling at different speeds, for example. Moreover, speed and maneuverability might help keep drivers safe. "When you're riding a motorcycle, you should always be riding defensively and take precautions. If you see something you might want to get away from, you should have that ability," he said.