young girl sitting in the back seat of a car
By IHPL - November 1, 2025

Every year, tens of thousands of lives are lost in United States alone to motor vehicle crashes.1 Those who are unrestrained or not properly restrained are at higher risk of morbidity and mortality from these accidents. According to the 2025 report by the Safe Transportation Research and Education Center (SafeTREC) at UC Berkeley, for example, 10,485 unrestrained passenger vehicle occupants were killed in motor vehicle crashes in 2023 nationally.2 Of those, 780 were from California.2

Given these sobering statistics and recent data suggesting that the current height requirement of 4 feet 9 inches for graduating out of booster seats does not adequately capture the safety needs of children in vehicles, the California State Assembly proposed AB 435, which was passed and signed into law by Governor Newsom on October 7.3

According to AB 435, children from 8 to 16 years of age will have to pass a five-step test to be considered properly restrained by a seat belt under the new California law effective January 1, 2027.4 Otherwise, they need to remain in a booster seat. The five-step test requirement is as follows:4

  1. The child is sitting all the way back against the auto seat.
  2. The knees of the child bend comfortably over the edge of the auto seat.
  3. The shoulder belt snugly crosses the center of the child’s chest and shoulder, not the child’s neck.
  4. The lap belt is as low as possible and is touching the child’s thighs.
  5. The child can stay seated like this for the entire trip.

All five of these requirements must be met in order to be considered compliant. If not, the driver could get a ticket and get fined $490.4

Since the new law is not effective until January 2027, Californians have some time to become familiar with the new requirement and adjust what they do for the child passengers in their vehicles. However, given the safety reasons for which the new law was put into place, it would be best to put them to practice right away, ensuring that vulnerable child passengers are safely secured to prevent or minimize morbidity and mortality in case of unfortunate motor vehicle crashes. 

Author Bio: 

Wonha Kim, MD, MPH, CPH, FAAP

Dr. Kim is the Director of the Institute for Health Policy and Leadership. She is also an Assistant Professor of Pediatrics and of Preventive Medicine at the School of Medicine and an Assistant Professor for the School of Public Health. Her research interests include pediatric obesity, social determinants of health, global health and policy approaches to addressing health issues faced by vulnerable populations.

References

  1. https://crashstats.nhtsa.dot.gov/Api/Public/ViewPublication/813756
  2. https://safetrec.berkeley.edu/2025-safetrec-traffic-safety-facts-occupant-protection-and-child-passenger-safety
  3. https://legiscan.com/CA/bill/AB435/2025
  4. https://leginfo.legislature.ca.gov/faces/billTextClient.xhtml?bill_id=202520260AB435
  5. https://calmatters.org/politics/2025/10/california-seat-belt-law/