SACRAMENTO -- Lane splitting.
It's a slick maneuver motorcyclists love, allowing them to cut between slower moving cars and shoot ahead. Car drivers, often startled, hate it -- calling it brazen and dangerous.
Is it safe? Is it legal? Hoping to clarify the practice, California officials have taken the unusual step of issuing a set of guidelines that affirm the move's legality but point out that there are only certain instances where it is considered safe.
California is the only state in the country that allows lane splitting, also known as "white lining," in which motorcyclists pass vehicles in adjacent lanes by driving between them.
California Highway Patrol officials said they've posted the first written guidelines on their website as part of a broader state highway safety initiative.
It comes as the number of motorcyclists in California is on the rise, as well as the number of motorcycle crashes.
"There is a need to acknowledge lane splitting is being done in California, and a need to help people understand what is reasonable," said CHP Sgt. Mark Pope. "Until now, no one in authority has said how to do it safely."
The guidelines say motorcyclists can ride between two cars if there is room, but must do it at no more than 10 mph faster than the vehicles they are passing.
The guidelines make clear that motorcyclists should not attempt the maneuver at full freeway speed or in any traffic going 30 mph or faster. That essentially means the fastest a motorcyclist should be going when lane splitting is 39 mph.
CHP officials say lane splitting is more risky at higher speed because motorcyclists have less time to react when something unexpected happens.
Banned in some states
Pope said the guidelines do not reflect new policy. The CHP long has held that lane splitting is legal in California because nothing in the state Vehicle Code prohibits it.
Nevada, Oregon, Washington and Arizona have explicit bans on lane splitting in their highway codes. Other states simply consider the maneuver unauthorized, according to the American Motorcyclist Association's national cycling rules database.
The practice is common in California. About 87 percent of California motorcycle riders reported that they split lanes, according to a recent state Office of Traffic Safety survey. Some motorcyclists call it lane sharing.
Several motorcycle activists lauded the guidelines for affirming California's unique lane-splitting privilege.
"They are very reasonable," said Greg Covel, executive director of ABATE of California, a motorcycle rights organization.
CHP officials say they sometimes ticket motorcyclists who are lane splitting, but citations are based on an officer's determination that the rider is going too fast for conditions or that the rider's lane changes are unsafe.
CHP numbers show that more than 9,600 people in California were injured in motorcycle crashes in 2010, the most recent year measured, up 25 percent since 2000.
But state officials say they know of no comprehensive studies focused on lane-splitting dangers, and they do not have data on the number of lane-splitting-related crashes. Police say they do get reports of side mirrors being ripped off and occasional crashes, including fatalities.
Motorcycle safety class instructors teach another technique, suggesting that cyclists ride on one side or the other of their lane, rather than in the middle.
That way cyclists can avoid the oilier part of the lane, as well as see ahead better and give themselves more avenues to get out of trouble, Covel said.
The state guidelines can be found at www.chp.ca.gov under the header "CHP Programs," by clicking on the headline "California Motorcyclist Safety." It also is viewable at www.ots.ca.gov, under "What's New at OTS."