The California Department of Motor Vehicles has joined the California Highway Patrol in withdrawing safety guidelines for motorcycle lane-splitting.
The agency confirmed late Tuesday that it had removed its online guidelines, and would also be removing guidelines from its printed literature.
"The DMV will not be including lane splitting language in the next revisions of handbooks in the next revision of 2015," said DMV Information Officer Jaime Garza, who added that the DMV had dropped the online language as of July 7.
The sometimes controversial act of lane-splitting, in which riders use the space between lanes when traffic is slow or has stopped, is legal in California -- the only state that does not actively outlaw the practice.
Until this month, the two agencies appeared to encourage it, or at least to encourage doing it safely.
"Lane splitting in a safe and prudent manner is not illegal in the state of California," the CHP's online literature began, before going on to recommend multiple safe lane-splitting tactics.
"Lane splitting should not be performed by inexperienced riders," said the DMV's driver handbook, before similarly advising on safe and unsafe lane-splitting techniques.
But sometime earlier this year, the CHP came under fire from a Sacramento-based individual who contended the police agency had exceeded its authority by recommending lane splitting.
The Office of Administrative Law agreed, and told the CHP to take down the guidelines.
Kenneth Mandler, the California state employee who filed the original complaint with the Office of Administrative Law, has not said why he is opposed to lane-splitting, and could not be reached for comment.
But anecdotal evidence suggests many drivers are uncomfortable with, or irritated by, lane-splitting.
So does research.
More than three-quarters of drivers interviewed for a 2012 study conducted by the California Office for Traffic Safety said they thought lane-splitting was unsafe. Almost half thought it was illegal. Two-thirds said they disapproved, and 7% admitted they had swerved to block a motorcycle trying to lane-split.
Since the CHP's decision was reported, motorcycle safety experts and motorcycling organizations have stepped up to voice their concerns about the future of lane-splitting, which supporters contend decreases traffic and helps motorcyclists' avoid overheating -- as most motorcycles are air-cooled and do not have radiators to keep their engines cool while standing still.
They also believe the practice increases rider safety by reducing the number of accidents involving motorcycles hit from behind while stuck in traffic jams -- the type of accident that accounts, National Highway Safety Transportation Administration research shows, for more than a quarter of all motorcycle accidents.
One study showed that lane-splitting nationally could prevent 18,000 freeway motorcycle accidents and up to 170 motorcyclist fatalities annually.
"Lane-sharing saves lives and reduces crashes," said motorcycle safety consultant Steve M. Guderian, an outspoken supporter of the practice.
Pointing out that lane-splitting is still legal in California, American Motorcycle Assn. western states representative Nick Haris said: "Motorcyclists are still using this long-recognized riding technique to relieve traffic congestion and improve safety. But now, neither riders nor motorists have a place to turn for authoritative guidelines on the practice."