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How Fault Is Decided After a Lane-Splitting Motorcycle Crash
California law allows lane splitting, so riding between lanes of slow or stopped traffic does not by itself make a rider at fault for a crash.
Fault turns on how each person rode and drove: the rider's speed compared with traffic, and whether the driver changed lanes or opened a door without looking.
California uses pure comparative fault, so a rider who shares some blame still recovers a reduced amount.
California law requires every rider and passenger to wear a DOT-compliant helmet.
A rider who was uninsured at the time loses the right to pain-and-suffering damages under Proposition 213.
The general deadline to sue is two years from the crash.
If a driver's insurer is blaming you because you were lane splitting, call (888) 713-6653 to talk through how fault is decided.
Vehicle Code § 21658.1 and Why Lane Splitting Is Legal in California
California defined lane splitting in 2016. Vehicle Code § 21658.1, added by AB 51 and in effect since January 1, 2017, describes it as "driving a motorcycle ... that has two wheels in contact with the ground, between rows of stopped or moving vehicles in the same lane."[1] The same section lets the California Highway Patrol write educational safety guidelines.
The statute does not say lane splitting is legal. It is legal because no California law prohibits it, and the CHP says so directly: "Lane splitting by motorcyclists is legal in California." No speed limit for lane splitting appears in the statute either. An early version of AB 51 capped it at 50 miles per hour and 15 miles per hour over traffic, and the Senate removed both limits before the bill passed.
Other states have since moved toward it. Utah, Arizona, and Colorado let riders filter between stopped vehicles at low speeds, Montana allows it past traffic moving 10 miles per hour or slower, and Minnesota began allowing it in moving traffic up to 25 miles per hour in 2025. California remains the only state whose law allows lane splitting at any traffic speed with no speed cap written into the statute.
For an injured rider, legality means the defense cannot treat lane splitting as negligence by itself, and has to show something unsafe about how the rider did it.
CHP Safety Tips and the 50 MPH Finding From the 2015 Berkeley Study
"A 2015 UC Berkeley study found lane splitting relatively safe in traffic moving 50 mph or less, with riders no more than 15 mph faster than other vehicles."
The CHP's current guidance gives riders no speed numbers. It tells them to consider the whole environment, including lane width, vehicle size, roadway, weather, and lighting, and warns that "the risk of death or serious injury during a lane splitting collision increases as speed and speed differential increases."[2] It adds that the far-left lanes are typically safer, that splitting beside big rigs, buses, and motorhomes should be avoided, and that riding on the shoulder is illegal and is not lane splitting.
The numbers people quote come from elsewhere. The CHP published guidelines in 2013 that mentioned staying within 10 miles per hour of traffic and avoiding splitting at 30 miles per hour or faster, then withdrew them after a complaint that they had been issued without the required rulemaking. The 50 and 15 figures come from the UC Berkeley Safe Transportation Research and Education Center's 2015 study for the state's Office of Traffic Safety.[3]
None of these figures is law, but insurers and juries use them as a yardstick, so the rider's speed and the speed of traffic around them are usually the first facts reconstructed after a lane-splitting crash.
Vehicle Code Rules Argued on Both Sides of a Lane-Splitting Crash
Because no statute governs how to lane split, both sides argue from general rules of the road. A violation of any of them can create a presumption of negligence under Evidence Code § 669.
| Rule | What it says | Who usually invokes it |
|---|---|---|
| Veh. Code § 22107 | No turning or moving right or left until it can be done with reasonable safety, and only after signaling | The rider, against a driver who changed lanes |
| Veh. Code § 22517 | No opening a door on the traffic side unless it is reasonably safe | The rider, against a driver or passenger who opened a door |
| Veh. Code § 22350 | No speed greater than is reasonable or prudent for the conditions | The driver, against a rider moving much faster than traffic |
| Veh. Code § 21658(a) | Drive as nearly as practical within a single lane, and change lanes only with reasonable safety | Both, depending on who drifted |
| Veh. Code § 21750(a) | Pass on the left at a safe distance without interfering with the vehicle being passed | The driver, against a rider who passed too closely |
| Veh. Code § 21460(b) | Do not cross double solid white lines, such as a carpool lane buffer | The driver, against a rider who split across a buffer |
The rule that applies depends on who moved, so the dashcam, nearby business video, and the damage to the bike and the car are usually what settle it.
Unsignaled Merges and Opened Doors in a Motorcyclist's Path
Most lane-splitting crashes happen when a driver moves into the space between lanes without seeing the motorcycle. A driver who changes lanes in slow traffic still has to do it "with reasonable safety" and signal first under § 22107, and a lane-splitting rider is a vehicle the driver is expected to look for.
- An unsignaled lane change in stopped or slow traffic
- A door opened into the space between lanes by a driver or passenger, which § 22517 prohibits unless it is reasonably safe
- A driver who swerves or shifts to block a rider, which the CHP tells drivers is illegal when done intentionally in a way that could cause harm
Insurers often open by saying the rider "came out of nowhere," and video or the angle of the damage usually shows who moved first.
Lane splitting is legal in California, and a lane change is a choice. In stop-and-go traffic, a motorcycle between the lanes is part of the picture every driver is supposed to check. More often than not the driver drifted into the gap without a signal, without checking, and the rider's place between the lanes does not move the blame onto the rider.
How Comparative Fault Splits a Lane-Splitting Crash, With the Numbers
Suppose a rider is splitting lanes through traffic moving about 20 miles per hour, going 15 miles per hour faster than the cars beside him, when a driver changes lanes without signaling and knocks him down. A jury finds his losses are $500,000, puts 70 percent of the fault on the driver for the unsafe lane change and 30 percent on the rider for his speed differential, and he recovers $350,000.
Under California's pure comparative fault rule, a rider found even mostly at fault still recovers his share. These cases are decided on their facts, usually by the speed difference and the driver's lane change.
Every percentage point an adjuster moves onto the rider comes off the recovery, which is why the speed of traffic at the moment of the crash matters as much as the rider's own speed.
How Helmet Use Under § 27803 Affects a Motorcycle Injury Claim
California has required helmets for every motorcycle rider and passenger since 1992. Vehicle Code § 27803 says a driver and any passenger "shall wear a safety helmet meeting requirements established pursuant to Section 27802," which incorporates the federal DOT standard.
A missing helmet does not make the rider at fault for the crash. The question is whether it made any injury worse. We are not aware of a published California appellate decision that has reduced a rider's damages for not wearing a helmet, and under the closest analogy, the seat belt rule in Housley v. Godinez (1992), the defense would have to prove with expert testimony which injuries a helmet would have prevented.[4]
Broken legs, wrist and shoulder injuries, chest injuries, and road rash have nothing to do with a helmet, so even where the argument is raised, it reaches only the head injuries.
Keep the helmet after a crash, damaged or not, because its condition is evidence of how the impact happened and what it protected against.
Motorcycle Crash Deaths and the Inland Empire's Rider Toll, 2023 to 2024
California recorded 583 motorcyclist deaths in 2023 and 522 in 2024, third in the country both years behind Florida and Texas, according to NHTSA's fatality data.[5]
The state's Office of Traffic Safety ranks counties on crashes weighted by population and miles driven, with first place the worst. On its 2023 table for motorcyclists killed and injured, San Bernardino County ranked 5th of 58 with 870 victims and Riverside County 6th with 929.[6] Los Angeles County had the most riders hurt or killed, 3,263, but ranked 29th once its size is taken into account.
The Inland Empire combines long, fast commuter corridors with heavy truck traffic, and the national picture is on our page about motorcycle crash claims across the country.
Behind these figures are riders with spinal injuries, amputations, and brain injuries whose claims turn on the same fault questions covered above.
How Much Is a California Motorcycle Accident Claim Worth?
A motorcycle claim is worth the rider's full losses, reduced by any share of fault, and motorcycle injuries tend to be severe, so insurance limits often decide how much is collected.
- Medical care, from the trauma center through surgery, rehabilitation, and future treatment
- Lost earnings and earning capacity, especially for riders whose work is physical
- Pain, suffering, and disfigurement, with no cap in a claim against a driver
- The motorcycle and gear, including the helmet and protective clothing
Minimum liability limits are $30,000 per person for policies issued or renewed since January 1, 2025, far less than a serious motorcycle injury costs. Your own uninsured and underinsured motorist coverage can fill the gap, as our page on underinsured motorist coverage in California explains. A rider who was uninsured at the time cannot recover pain-and-suffering damages at all under Proposition 213.
A motorcycle policy can carry different limits from a car policy in the same household, so checking every policy is part of finding the money in these cases.
How Long an Injured Motorcyclist Has to File in California
A lawsuit against the driver must generally be filed within two years under Code of Civil Procedure § 335.1.
- Six months for a written claim against a city, county, or Caltrans when a pothole, debris, uneven pavement, or a missing sign contributed, which matters more for riders than for drivers
- Two years to settle, sue on, or demand arbitration of an uninsured motorist claim
- 24 hours to report a hit-and-run to police for an uninsured motorist claim against an unidentified driver
Road-condition claims against public agencies have their own rules, set out on our page about claims against a California public entity.
Photographs of the road surface at the crash site, taken before it is repaired, are the evidence a road-defect claim depends on.