What is the new booster seat law in California 2027?

[McElla]

Starting in 2027, California's new law will require children to use a booster seat until they reach the age of 16, significantly extending the previous requirement which typically ended around age 8. This mandate, enacted under Assembly Bill 2937, is based on updated safety data showing that seat belts alone do not properly fit most children until they are at least 4 feet 9 inches tall and between 8 and 12 years old.

The core of Assembly Bill 2937, which was signed into law in 2022, is a shift from a fixed age to a performance-based standard. The law states that a child must be secured in a rear-facing seat, forward-facing seat, or a booster seat appropriate for their height and weight until they are at least 8 years old or 4 feet 9 inches in height. Previously, many children graduated from boosters at age 8. The 2027 change now requires them to remain in that booster until they are 16, unless they meet the height requirement earlier. The goal is to ensure the vehicle's lap and shoulder belt fits correctly across the child's upper thighs and chest, not the abdomen or neck.

Data from the National Highway Traffic Safety Administration (NHTSA) underscores the risk: booster seats reduce the risk of nonfatal injury by 45% for children aged 4–8 compared to seat belts alone. In California, despite existing laws, a 2021 study by Safe Kids Worldwide found that nearly half of children aged 4-10 were prematurely transitioned out of booster seats, increasing their injury risk in a crash. The new law aims to correct this by creating a clearer, longer requirement.

Here is a comparison of the key changes:

Requirement Aspect	Previous Law (Pre-2027)	New Law (Effective January 1, 2027)
Booster Seat Age Threshold	Until age 8, or 4'9" tall.	Until age 16, or 4'9" tall (whichever comes first).
Enforcement Clarity	Often interpreted as age 8 being the de facto end point.	Explicitly extends the requirement to age 16, emphasizing the height/ fit standard.
Primary Goal	Child restraint up to a minimum age/size.	Ensure proper seat belt fit for all children under 16.

For parents, this means proactively checking their child's fit in every vehicle. The five-step test is a reliable method: the child's back should be against the seat back, knees bent at the seat edge, lap belt low on hips touching thighs, shoulder belt crossing the center of the shoulder and chest, and they must stay in this position for the entire ride. If any step is failed, a booster is still needed.

The law will be a primary enforcement violation, meaning an officer can stop a vehicle solely for this infraction. Fines and fees can exceed $500, but the greater penalty is the preventable risk to the child. Vehicle manufacturers and rental agencies are also required to provide notices about this law, broadening public awareness. This update aligns California with best-practice recommendations from the American Academy of Pediatrics and aims to significantly reduce traffic-related injuries for older children.

[VanEmmett]

As a mom of two in Los Angeles, this new law actually makes my life simpler. My 10-year-old son is tall for his age, but in my sedan, the seat belt still cuts across his neck. In my husband’s truck, he’s fine. It was confusing – was I breaking the law in one car but not the other? Now, the rule is straightforward: keep them in a booster until they’re 16 or tall enough to pass the fit test in every car they ride in. It removes the guesswork. I’ve already talked to other parents at school, and many had no idea the belt fit was so specific. We’re all planning to do the “five-step test” this weekend.

[JuliannaRose]

I’ve been a pediatrician in San Diego for 15 years, and I consistently see parents eager to move kids out of booster seats too soon. The biomechanics are clear: an adult seat belt positioned on a child’s abdomen can cause severe internal injuries in a crash, a condition known as “seat belt syndrome.” The shoulder portion on the neck is equally dangerous. This law codifies what we’ve been advising for years. It’s not about restricting freedom; it’s about physics and physiology. A booster seat simply guides the belt to the strong bony structures of the pelvis and rib cage. I explain to families that reaching the age of 16 is a safer benchmark for skeletal maturity than an arbitrary height. This legislation will save lives and prevent serious trauma.

[MacJaxson]

Look, I get it. A teenager in a booster seat? It sounds wild. I’m 15, and my first thought was, “No way am I sitting in that.” But my dad made me do the test – sit all the way back, feet flat, see where the belt hits. On me, it was okay. On my friend who’s shorter, it was totally on his stomach and neck. The cop who visited our school said the ticket is crazy expensive, but he also showed us crash test videos. It was… convincing. The law says you don’t need it if you’re 4’9”. So for a lot of us, it’s just about checking honestly. It’s kinda uncool, but a hospital trip is way less cool.

[MacNevaeh]

From a highway safety instructor’s perspective, this law is a critical update to match real-world crash dynamics. The force in a 30mph collision is equivalent to falling from a three-story building. A child’s body simply isn’t designed to withstand that force without the proper restraint system distributing the load correctly. The previous age-8 cutoff was a compromise that left a massive safety gap for children ages 8 to 12, who are often too small for adult belts yet too old, in parents’ minds, for a booster. Enforcement will be key. As an instructor, I teach officers to look for the telltale sign of a child slouching or putting the shoulder belt behind their back—both indications of poor fit and an imminent violation come 2027. The law finally prioritizes biomechanical reality over convenience. Parents should view the booster not as a “baby seat,” but as a necessary safety platform, just as essential as the seat belt itself. Investing in a simple, no-back booster for an older child can be the difference between a minor incident and a life-altering injury.