A previous state law required car seats or booster seats for kids until they were 6 years old or weighed 60 pounds.
"This new law will help protect more children from being injured during a crash," said Patrice Christensen, a registered nurse and coordinator of the San Mateo County Emergency Medical Services injury prevention program.
Kids aged 8 years and older are ready to ride without a booster seat when the child can sit against the back of a vehicle seat with knees bent, without slouching and can comfortably stay in that position.
The lap belt should also be low on the hips and touch the upper thighs with the shoulder belt crossing the shoulder and chest without touching the child's face or neck.
Drivers who are caught not complying with the new state law can face fines starting at $475.
For information on the new law or for help determining if a child still needs a booster seat, call Patrice Christensen at (650) 573-3728, contact a local California Highway Patrol office or go online at www.cdph.ca.gov/vosp.