when can a child use a booster
Stephanie Tombrello. child passenger safety specialist. You can safely switch your child to a booster seat if she's at least 4 years old and she weighs 40 pounds or more or has grown too tall for her car seat (when her shoulders are higher than the top set of harness-strap slots in the car seat's back).tephanie Tombrello. child passenger safety specialist. You can safely switch your child to a booster seat if she's at least 4 years old and she weighs 40 pounds or more or has grown too tall for her car seat (when her shoulders are higher than the top set of harness-strap slots in the car seat's back).