Lane Splitting in California: Your Legal Rights Explained

The Law: What California Vehicle Code § 21658.1 Actually Says

For decades, lane splitting existed in a gray area—it wasn’t expressly legal, but it wasn’t prohibited either. That changed with Assembly Bill 51, which added § 21658.1 to the Vehicle Code.

The statute defines lane splitting as:

“Driving a motorcycle… with two wheels in contact with the ground, between rows of stopped or moving vehicles in the same lane.”

That definition matters.

What the law gives you

• Legitimacy: A rider cannot be cited solely for lane splitting. It is a lawful maneuver.
• Authority to regulate safety: The statute authorizes the California Highway Patrol (CHP) to issue lane-splitting safety guidelines.

Those guidelines are not criminal statutes—but in the real world, they are how fault is determined after a crash.

The CHP Guidelines: The “10 MPH Rule” and Why It Matters

Because the Vehicle Code does not set a numerical speed limit for lane splitting, police officers, insurance adjusters, and accident reconstruction experts rely heavily on CHP guidance.

Two factors dominate nearly every investigation.

1. Speed Differential (The “10 MPH Rule”)

The most important factor is not your absolute speed—it’s the difference between your speed and surrounding traffic.

• Generally considered safe: Riding no more than 10 mph faster than traffic
• High risk: Flying past stopped or slow traffic at high speed

As the speed differential increases, drivers have less time to see you, and you have less time to react to sudden lane changes. Large speed differentials are routinely cited as evidence of unsafe riding—even though lane splitting itself is legal.

2. Traffic Speed Threshold

CHP guidelines advise against lane splitting when traffic is moving faster than approximately 30 mph.

Why? At higher speeds:

• Gaps close faster
• Lane changes happen more abruptly
• Reaction time drops sharply

Legal reality: If you are splitting lanes at freeway speeds and are hit, investigators may cite “unsafe speed for conditions” under CVC § 22350—even if the maneuver itself was lawful.

Fault After a Crash: When the Car Driver Is Liable

A persistent myth is that motorcyclists are always at fault when lane splitting. That is simply false.

Drivers owe motorcyclists the same duty of care they owe other vehicles. In many lane-splitting collisions, the car driver—not the rider—is liable.

Unsafe Lane Changes (CVC § 21658(a))

Drivers must signal and ensure a lane change can be made safely. Sudden swerves into adjacent lanes without checking mirrors or blind spots are a common cause of motorcycle collisions.

Key questions investigators ask:

• Did the driver signal?
• Did they check mirrors and blind spots?
• Was the movement abrupt or aggressive?

Lane Drift and Distraction

Drivers are required to remain “as nearly as practical entirely within a single lane.” Distracted driving that causes a vehicle to drift onto the lane divider—squeezing a rider—is negligence.

Intentional Blocking: Flatly Illegal

Some drivers believe they can “teach motorcyclists a lesson” by blocking or crowding them. That conduct is not just dangerous—it is illegal.

Relevant laws include:

• CVC § 22400: Prohibits driving so slowly as to impede traffic
• CVC § 22517: Prohibits opening a door into moving traffic (“dooring”)

Intentional swerving, blocking, or dooring can elevate a civil case from negligence to intentional misconduct, and in extreme cases may implicate criminal liability.

Common Insurance Defenses—and How They’re Defeated

After a lane-splitting crash, insurance companies follow a predictable playbook.

“He Came Out of Nowhere”

The defense:

“My insured looked, but the motorcycle was going so fast it appeared out of nowhere.”

The counter:
Video evidence showing a modest speed differential collapses this argument. If footage shows the rider traveling slightly faster than stopped traffic, fault shifts to the driver’s failure to look.

“He Was Riding the Line”

The defense:

“He wasn’t in a lane—he was riding the paint.”

The counter:
That is the definition of lane splitting. California law explicitly permits riding between rows of vehicles.

The Science: Why Lane Splitting Improves Safety and Traffic Flow

CHP frequently cites research from UC Berkeley’s SafeTREC program, which analyzed thousands of motorcycle collisions.

Key findings:

• Lane splitting is comparatively safe when traffic is moving under 50 mph and speed differentials are low
• Lane-splitting riders are significantly less likely to be rear-ended
• Traffic congestion decreases when motorcycles do not occupy full vehicle spaces

In stop-and-go traffic, rear-end collisions are one of the most common and dangerous risks for riders. Lane splitting reduces that exposure.

How to Protect Yourself After a Lane-Splitting Crash

Bias often works against motorcyclists. Evidence matters.

Practical steps that strengthen your case

• Helmet or GoPro camera: This is often decisive. Speed, traffic flow, and driver behavior become objective facts.
• Lane choice: CHP recommends splitting between the #1 and #2 lanes. Splitting near on-ramps or far-right lanes is riskier and more easily criticized.
• Scene documentation: Photos showing skid marks near lane dividers—not shoulders—help establish lawful positioning.

Bottom Line

Lane splitting is legal in California—but fault is decided on how it is done.

When riders split at reasonable speeds and drivers fail to look or act recklessly, liability often falls squarely on the driver. Understanding the legal framework—and preserving evidence early—can be the difference between a denied claim and full compensation.

Reminder:
This content is for informational purposes only and should not be relied upon as legal advice. Every case is different. If you have questions about your rights or deadlines, consult a qualified attorney promptly.