California Vehicle Code Section 21658.1 is the state law that formally defines motorcycle lane splitting and makes California the only state to recognize the practice in its vehicle code. It took effect on January 1, 2017, and does two things: it defines what lane splitting is, and it authorizes the California Highway Patrol to publish safety guidelines for riders.1California Legislative Information. California Vehicle Code 21658.1 It sets no speed limit and creates no penalty of its own.
What the Statute Says
The section has three subsections, and each has a narrow job.
Subsection (a) defines lane splitting as driving a motorcycle 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, and highways.1California Legislative Information. California Vehicle Code 21658.1 The two-wheel requirement is doing real work: trikes and three-wheeled motorcycles fall outside the definition and are not covered by this statute.
Subsection (b) gives the CHP authority to develop educational guidelines for lane splitting that protect the safety of the rider and the people in the vehicles around them. Subsection (c) requires the CHP to consult with the DMV, Caltrans, the Office of Traffic Safety, and at least one motorcycle safety organization when putting those guidelines together.2California Legislative Information. California Code VEH 21658.1 – Lane Splitting
That is the whole statute. There is no fine, no point schedule, no speed cap. A rider who splits lanes dangerously can still be cited under other Vehicle Code sections covering unsafe speed or reckless driving, but Section 21658.1 itself is purely definitional.
The CHP Safety Guidelines
The guidelines the CHP publishes under subsection (b) are not enforceable rules, but they matter in practice because officers, adjusters, and courts treat them as the yardstick for whether a rider was splitting safely:
- Ride no more than 10 mph faster than the surrounding traffic.
- Lane splitting is not advised when traffic is flowing at 30 mph or faster.
- Avoid splitting near freeway on-ramps and off-ramps, where cars are most likely to change lanes suddenly.
A rider who follows these numbers is operating within what the state considers safe practice. A rider who ignores them is still not violating Section 21658.1, but their conduct may support a citation under another section or hurt them in a civil claim.
How It Affects Fault in a Crash
Because lane splitting is legal, a rider is not automatically at fault for a collision just because they were splitting lanes when it happened. California follows comparative negligence, which means more than one party can share blame and each party’s recovery is reduced by their share.
What determines fault is how everyone was actually driving. A motorcyclist moving 10 mph faster than crawling traffic is in a very different position than one weaving at 50 mph between cars. Adjusters and courts look at the speed differential, whether the rider’s path was predictable, and whether a driver made a sudden lane change or opened a door without checking. The CHP guidelines function as the informal benchmark in that analysis.
Drivers also have obligations. It is illegal to intentionally block or impede a lane-splitting motorcyclist in a way that could cause harm.3California Highway Patrol. California Motorcyclist Safety Program Opening a door to startle a rider, drifting toward the lane line to close a gap, or straddling two lanes to prevent a motorcycle from passing can all shift liability onto the driver.
How California Compares to Lane Filtering States
California is alone in formally defining lane splitting, but a handful of other states allow a narrower practice called lane filtering. The distinction matters if you ride in more than one state, because the conditions are not the same.
Utah, Montana, Arizona, Colorado, and Minnesota have each legalized some form of lane filtering, and each attaches conditions California does not. Arizona limits filtering to roads with speed limits of 45 mph or less and requires surrounding traffic to be fully stopped. Montana allows it when traffic is stopped or moving under 10 mph and caps the rider at 20 mph. California’s statute applies at any speed, on any road, and places no statutory cap on the rider. The CHP guidelines close part of that gap, but a guideline carries less weight than a hard legal limit.
What Section 21658.1 Does Not Cover
Section 21658.1 is frequently confused with Section 21655.8, which governs how any vehicle enters and exits an HOV (carpool) lane. They are separate statutes answering separate questions. Section 21658.1 is only about riding between rows of vehicles in the same lane; it says nothing about carpool lane access, double solid lines, or occupancy exemptions. A motorcyclist can be subject to both laws on the same stretch of freeway, but the rules, exemptions, and penalties under Section 21655.8 come from that other section, not from 21658.1.