Who Has to Wear a Seat Belt in California, and What Changes in 2027?

What the law says today: Vehicle Code 27315

Section 27315, the Motor Vehicle Safety Act, applies to passenger vehicles, motortrucks and truck tractors, but not motorcycles. Its core duties are:

• The driver may not operate the vehicle on a highway unless the driver and all passengers 16 or over are properly restrained by a safety belt (subdivision (d)(1)).
• Each passenger 16 or over may not ride unless properly restrained (subdivision (e)), so an adult passenger can be cited personally.
• The owner must keep the safety belts in good working order (subdivision (f)).

Under the version in force through 2026, "properly restrained" means the lap portion crosses the hips or upper thighs and the shoulder portion, if there is one, crosses the chest in front of the occupant. A shoulder belt tucked behind the back or under the arm does not meet that definition.

A violation is an infraction punishable by a fine of not more than twenty dollars for a first offense and not more than fifty dollars for each later one. For a first offense the court may order a seat belt program or traffic school instead of the fine.

What changes on January 1, 2027

Assembly Bill 435 (Statutes of 2025, Chapter 434) rewrote the definition. From January 1, 2027, a person is properly restrained only if they meet all five steps:

1. Sitting all the way back against the seat.
2. Knees bending over the edge of the seat.
3. Shoulder belt snugly crossing the center of the chest and shoulder, not the neck.
4. Lap belt worn at its lowest position, touching the thighs.
5. Able to stay seated like this for the whole trip.

The same five-step test is written into the 2027 versions of the child passenger sections, so it decides when an older child may move out of a booster and into the belt alone.

What it means in practice

Who gets the ticket depends on age. For passengers under 16, the duty falls on the parent, guardian or driver under the child passenger sections. For passengers 16 and up, the passenger is responsible for their own belt, and the driver also has a duty to ensure everyone 16 and over is restrained.

The section has a medical exemption: it does not apply to a person whose physically disabling or medical condition would prevent appropriate restraint, if a licensed physician and surgeon or a licensed chiropractor certifies the condition and states why a belt is inappropriate. Carry that certificate.

Does not wearing a belt affect an injury claim?

Subdivision (i) answers part of this directly. In a civil case, a seat belt violation "does not establish negligence as a matter of law or negligence per se for comparative fault purposes," but negligence "may be proven as a fact without regard to the violation." In plain terms, the ticket itself does not decide the case, but the other side can still try to show that not buckling up made the injuries worse. How your own policy's medical coverages treat an unbelted occupant varies by insurance company, so check your policy wording.

What to do

1. Buckle before the car moves, and make it the rule for every seat.
2. Run the five-step check now on teens and smaller adults; the 2027 standard is about fit, not just whether the buckle is latched.
3. If a belt is frayed, retracts poorly or will not latch, fix it. Keeping belts working is the owner's legal duty.
4. If you rely on the medical exemption, keep the signed certificate in the vehicle.

When you are reviewing your coverage for the people who ride with you, you can compare quotes here, including medical payments options.