Lane splitting in California

More misinformation attaches to lane splitting than to any other subject in California motorcycle law, and most of it comes from numbers that were never in a statute. Getting this right matters, because the misinformation is what an adjuster will use against a rider. This is general information, not legal advice.

What the statute says

A 2016 law added Vehicle Code section 21658.1. It has exactly three subdivisions:

• (a) defines "lane splitting" as riding a two-wheeled motorcycle between rows of stopped or moving vehicles in the same lane, including on divided and undivided streets, roads, and highways.
• (b) authorises the CHP to develop educational guidelines relating to lane splitting, in a manner that would promote motorist and motorcyclist safety.
• (c) requires consultation with specified agencies and organisations in developing those guidelines.

That is the whole section. It has not been amended since it was enacted by AB 51 in 2016, effective January 1, 2017.

Sources: Veh. Code, § 21658.1 (lane splitting defined and authorised; subd. (b) authorises CHP educational guidelines).

There is no legal speed limit for splitting

Two figures circulate as though they were law: split no more than 10 mph faster than surrounding traffic, and do not split above 30 mph. Neither appears in the statute or in any other California statute.

They came from CHP educational guidelines, which were withdrawn in 2015 following a challenge to how they had been adopted. The current CHP guidance is principle-based rather than numeric — ride at a speed appropriate to conditions, consider the gap and the surrounding traffic, and be visible. It is guidance, published under the authority of subdivision (b). It is not law and a rider cannot violate it.

What does apply is the basic speed law: no person may drive at a speed greater than is reasonable or prudent for the conditions, and never at a speed endangering persons or property. Splitting too fast is unsafe speed, judged like any other unsafe speed.

Sources: Veh. Code, § 22350 (basic speed law).

What the CHP guidance does say

The current guidance also addresses drivers, telling them not to intentionally block or impede a motorcyclist who is splitting and not to open a door to impede one. That is worth knowing and worth stating accurately: it is guidance issued under section 21658.1(b), not a provision of the statute.

The door point does have a statutory home. Vehicle Code section 22517 makes it unlawful to 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 traffic, and unlawful to leave one open longer than necessary.

Sources: Veh. Code, § 22517 (opening or leaving open a door on the traffic side); CHP motorcyclist safety guidance.

How it actually gets argued

A defence will treat splitting as recklessness and ask for a large fault percentage on that basis alone. The law does not support that, and the answer is to move the argument onto the facts that do matter:

• The rider's actual speed, from data or reconstruction rather than estimate.
• The speed differential between the motorcycle and surrounding traffic.
• The width of the gap the rider was moving through.
• Whether traffic was stopped or moving, which changes the risk profile entirely.
• What the driver did — an unsignalled lane change into an occupied space is the classic fact pattern.
• Conditions — lane width, weather, visibility, time of day.

A rider splitting at a modest differential through stopped traffic is in a very different position from one passing between moving cars at highway speed. The doctrine that turns those facts into numbers is at comparative fault, and the broader problem of jurors and adjusters starting from a poor view of riders is at bias against riders.

Common questions

Is lane splitting legal in California?

Yes. California expressly authorised it in 2016 and is the one state that has done so by statute. Vehicle Code section 21658.1 defines it as riding a two-wheeled motorcycle between rows of stopped or moving vehicles in the same lane, on divided or undivided roads.

Is there a speed limit for lane splitting?

No. The statute states no maximum speed and no speed-differential figure. The often-quoted "10 mph faster than traffic" and "not above 30 mph" came from CHP guidelines that were withdrawn in 2015. They were never law and they are not law now.

So can I split at any speed?

No, but the rule that governs is the ordinary one. Splitting too fast for the conditions is judged under the basic speed law, exactly as any other unsafe speed is. There is simply no lane-splitting-specific speed statute to violate.

Will splitting make me at fault for the crash?

Not by itself. Fault is a comparative question and legal conduct is not a fault percentage. What matters is the rider’s actual speed, the difference between that and surrounding traffic, the width of the gap, and whether traffic was stopped or moving.