On January 1st, 2017, California became the first US state to legalize “lane-splitting”, also known as “lane-sharing” and “traffic filtering.” It is the well known practice in California of riding between cars on motorcycles.
Lane-splitting is thought to have originated because all motorcycle engines were once entirely air-cooled and would quickly overheat if not kept moving. More modern engines have radiators similar to cars, but they are necessarily small to fit on a motorcycle and still designed to assist with air movement to keep the engine cool.
How Law May Affect Motorcycle Accident Rates
The law’s aim is safety, and was also intended to allow the California Highway Patrol to issue guidelines. Though counter-intuitive, various studies have concluded that personal injury accidents are reduced and traffic congestion decreases when motorcyclists are allowed to drive between cars in slow and stop-and-go traffic.
Congested traffic was a factor in nearly 60% of motorcycle accidents in one study, while California had significantly fewer motorcycle fatalities from rear-end collisions than other states that prohibit lane-splitting.
It was reported in a 2015 UC Berkeley study that lane-splitting motorcyclists were twice as likely to rear-end a vehicle than be rear-ended themselves; however, as a motorcycle accident attorney, I know know that when motorcyclists are the victims in a car accident, they are far more likely to be severely injured than the driver of a car or truck.
Lane-Splitting Illegal in Most of US
All other states prohibit the practice, but it is legal in most of Europe and Asia—and until Assembly Bill 51 was signed by Governor Jerry Brown, California had not officially recognized the practice, so lane-splitting had been in a gray area of being neither legal nor illegal.
While the new law is a starting point, and mostly just defines the practice of splitting lanes in order to recognize its legality in the vehicle code, there have been laws for how motorists respond to lane-splitting for many years. Moving a vehicle in order to impede a motorcycle is considered a lane-change violation, and the motorist could be cited.
Likewise, many a commuter’s guilty fantasy of opening a car door to stop a lane-splitting motorcyclist is also a violation.
Many motorists stuck in traffic feel that motorcyclists are “cheating” by driving between cars and essentially “making up a lane” where one doesn’t exist. In an ongoing and unscientific poll from Sacramento’s KFBK, 64% have voted that motorcycles splitting lanes is “dangerous and unfair to cars stuck in traffic.”
Advantages Other Than Motorcycle Safety
In many traffic-dense European and Asian cities, motorcyclists, bicycles and various smaller vehicles are expected to “filter through” traffic. And while to US residents the images of a jumble of vehicles taking up the entire road appears unsafe, it’s considered normal and accomplishes moving more people and goods over a limited amount of road more effectively.
There are also health and environmental benefits to traffic filtering. For the rider, progressing through slower traffic reduces exposure to concentrated exhaust, while continuously moving — rather than stopping and starting — also results in better mileage and reduced pollution from motorcycles.
A recent case study in Brussels concluded that if the percentage of motorcycles in typical commute traffic were 10% (it’s currently at around 1%), and most practiced lane-splitting, congestion would be reduced by 63%.