Yes, lane splitting is legal for motorcycles in California. It is the only state in the United States where lane splitting is explicitly permitted under certain conditions. The California Vehicle Code Section 21658.1 defines lane splitting as a motorcyclist riding between rows of stopped or moving vehicles in the same lane.
The legislation does not provide specific guidelines on how to perform lane splitting safely, but it allows the California Highway Patrol (CHP) to develop educational guidelines in collaboration with other traffic safety organizations. The CHP published guidelines in 2013 and updated them in 2016 to provide motorcyclists with recommendations for safe lane splitting.
Regarding evidence and research on lane splitting and motorcycle safety, a study conducted by the University of California Berkeley's Safe Transportation Research and Education Center (SafeTREC) in collaboration with the California Office of Traffic Safety (OTS) was published in 2015. The study analyzed crash data from California between June 2012 and August 2013.
The key findings of the study suggested that lane splitting, when done within certain speed differentials and traffic conditions, can be done safely. It found that motorcyclists who engaged in lane splitting were less likely to suffer head injuries and were also less likely to be rear-ended compared to motorcyclists who did not engage in lane splitting.
The study also highlighted that the safety of lane splitting depends on factors such as speed differential, traffic speed, and the width of the lanes. It recommended that additional education and guidelines be developed to promote safe practices.
It is worth noting that research on lane splitting and its safety impacts is limited, and more comprehensive studies are needed to provide a more detailed understanding of its effects on motorcycle safety. However, the existing research indicates that when done responsibly and within reasonable limits, lane splitting can be performed safely.