For infants and toddlers up to 40 pounds, the safest way to travel is using a five-point harness. In California, children must ride in an appropriate booster or safety seat in the back of the car until they are six-years-old or weigh at least 60 pounds.
While some states stipulate a height requirement for car seats and booster seats, California concentrates primarily on age and weight requirements.
In California, if children weigh less than 20 pounds, they must be in a rear-facing car seat in the back seat if there is one. If they weigh more than 20 pounds, depending on their age, you can face them forward, still in a car seat. Children more than 40 pounds may be strapped into a booster seat using the car seat belts. They must be in a booster seat until they weigh 60 pounds or more.
In California, children under one year of age must be in a rear-facing car seat. If the child is more than one-year-old and also meets the weight requirement, they can face forward. There is no age requirement for transitioning to a booster seat, but children must remain in a booster seat until they are six-years-old or meet the weight requirement.