Lane Splitting Accident in California: Who Is at Fault

You were splitting lanes through slow traffic and a car came across the line into you. Now an adjuster is explaining that because you were between lanes, the claim is worth a fraction of what it would otherwise be, or nothing at all.

That is a negotiating position, not California law. This post covers what the lane splitting statute actually says, why the "30 mile per hour rule" everyone quotes is not a rule, and how fault really gets divided after a lane splitting crash.

Lane splitting is legal, and the statute is shorter than you think

Start with the statute, because it is shorter than anyone expects. Vehicle Code § 21658.1(a) defines lane splitting as "driving a motorcycle, as defined in Section 400, that has two wheels in contact with the ground, between rows of stopped or moving vehicles in the same lane, including on both divided and undivided streets, roads, or highways."

Notice what is not there. It defines lane splitting; it does not restrict or condition it. Subdivision (b) says the CHP "may develop educational guidelines relating to lane splitting in a manner that would ensure the safety of the motorcyclist and the drivers and passengers of the surrounding vehicles." That is permission to publish advice, not authority to write an enforceable speed limit.

That matters more than it sounds. California's presumption-of-negligence instruction, CACI No. 418, tells a jury that if a party proves the other side violated a law and that the violation was a substantial factor in bringing about the harm, the jury must find that person negligent. That shortcut is not available against you here, because there is no law against lane splitting to violate. To pin fault on you, the insurer has to prove you actually rode unreasonably on the facts.

The "30 mph rule" is not a rule

Almost every conversation about lane splitting produces the same two numbers: do not split when traffic is moving faster than 30 miles per hour, and do not ride more than 10 miles per hour faster than the traffic around you.

Those numbers came from a CHP educational handout, and the CHP took it down. CBS News Bay Area reported in July 2014 that the agency pulled the guidelines because people were reading them as enforceable law. A CHP officer said they "were merely intended as common-sense traffic safety tips." The document had advised never exceeding 10 mph faster than surrounding traffic and not splitting above 30 mph.

The CHP publishes lane splitting tips again today on its California Motorcyclist Safety page, and the numbers are not in them. What that page offers is qualitative: consider the total environment, including lane width, vehicle size, and roadway, weather and lighting conditions. Danger increases at higher speed differentials and as overall speed increases. It is typically safer to split between the far left lanes, away from large vehicles and out of blind spots. One line there is worth memorizing: riding on the shoulder is illegal and is not considered lane splitting.

So when an adjuster says you broke the 30 mile an hour rule, ask which code section that is. There is not one. Your speed and the speed differential do still matter, because they feed the ordinary reasonableness question, which is why you should not be estimating either one out loud on a recorded call before you have seen the report. Our post on recorded statement traps covers what those calls are built to produce.

What the driver was required to do

While the insurer works on your conduct, look at theirs. These are real statutes, and CACI 418 runs in your direction when one of them is broken.

• Vehicle Code § 22107. "No person shall turn a vehicle from a direct course or move right or left upon a roadway until such movement can be made with reasonable safety and then only after the giving of an appropriate signal ..." Most lane splitting crashes are this exact thing: an unchecked lane change into a gap that was not empty.
• Vehicle Code § 22517. No person shall open a vehicle door on the side available to moving traffic "unless it is reasonably safe to do so and can be done without interfering with the movement of such traffic."

The CHP's messages to drivers sit on the same page as its rider tips: lane splitting is legal in California, intentionally blocking or impeding a motorcyclist in a way that could cause harm to the rider is illegal, opening a door to impede a motorcyclist is illegal, and drivers in the far left lane should move left to give riders room. If a driver drifted toward the line when they saw you coming, that page belongs in front of the adjuster.

What the adjuster will try to pin on you

Expect a fault percentage attached to you early, before anyone has measured a sight line or pulled a signal module. The questions are predictable:

• How fast you were going, and how fast traffic was. You will be asked three different ways, because the gap between the two answers is the whole argument.
• Where you were in the lane. Blind spot position gets used against riders constantly.
• What you were wearing, and whether the bike was modified. Dark gear, no reflective material, aftermarket lighting or mirrors.
• Whether any of it happened on the shoulder. That one is a real legal problem, so be accurate rather than vague.

None of this ends a claim. California follows pure comparative negligence: a share of fault reduces a recovery, it does not erase it. A confident fault percentage delivered in week one is a negotiating move, not a finding.

The helmet question

California requires helmets for every rider, so this comes up whenever yours was off or loose. Section 27803(a) says a driver and any passenger "shall wear a safety helmet meeting requirements established pursuant to Section 27802 when riding on a motorcycle ..." Subdivision (e) defines wearing: a conforming helmet on the head, fastened with the helmet straps, sized to fit securely "without excessive lateral or vertical movement." A helmet clipped to the sissy bar is not being worn, and neither is an unbuckled one.

Keep the two halves apart. A helmet argument goes to the injuries a helmet would have prevented. It says nothing about who caused the crash, and nothing about a broken tibia. Even when it lands, it reduces a recovery rather than ending it.

What this means in California

• Two years. Code of Civil Procedure § 335.1 generally gives you two years from the date of injury to file a personal injury action.
• Six months if a public entity is involved. Pavement seams, metal plates, and surface defects hurt riders far more than drivers, and a claim against a city, county, transit agency or Caltrans is usually due within six months. See our post on the six-month government claim deadline.
• Pure comparative negligence. Partial fault cuts your recovery by your share instead of barring it.
• The driver's limits may not be enough. Since January 1, 2025, Vehicle Code § 16056 sets California's minimum liability coverage at $30,000 for bodily injury or death to one person, $60,000 for all persons, and $15,000 for property damage. That is a floor, and a motorcycle injury runs through it fast, which is why your own uninsured and underinsured coverage matters. Our post on being hit by an uninsured driver covers how it is calculated and the separate deadline attached to it.

Practical next steps

Get medical care and keep the appointments, because a gap in treatment is the first thing an adjuster points to later. Photograph the bike, the road, the lane lines, and the other car's position before anything moves, and request the collision report.

Do not repair the bike or clean your gear yet. Your helmet, jacket, and gloves are evidence of both impact and visibility, so bag them and leave them alone. Get names and numbers from the people stopped in traffic around you, because those witnesses scatter. Notify your own insurer and ask for your declarations page. If you want someone to sort out how much of that fault percentage is real, a consultation with our firm is free and there is no fee unless there is a recovery.