When a child is too big for a harnessed car seat, it's time to use a booster seat. A child is to be considered "too big" if he/she exceeds the manufacturer's weight limit or the top of his/her head is higher than the top of the seat. Usually a child will need a booster seat between the ages of four and six.
We found out earlier that a seatbelt is designed to sit across the pelvis and ribcage, spreading the force of an impact over the strongest parts of our skeleton. A booster seat works by raising the child so that the adult seatbelt fits across these areas. Since the car's built-in seatbelt is being used, booster seats do not have an integral harness to hold the child in place; instead, the seatbelt holds in both the child and the seat. This means that it is extremely important to ensure the belt is correctly adjusted.
You want to make certain that:
- The belt is fastened securely and is as tight as possible.
- The belt should go over the pelvic region, not the stomach.
- The diagonal strap should rest over the shoulder, not the neck.
Usually by the age of six, or when a child can sit up straight on their own, without slumping or slouching, he/she can graduate from a full booster seat to a backless booster seat. A backless booster seat is simply a standard booster seat without the backrest. As with other car seats, you can find convertible booster seats that transition from a backrest-inclusive model to backless. It's important to remember that, when sitting in a backless booster seat, your child should sit up straight so that the diagonal strap of the seatbelt rests on your child's shoulder and not across his/her neck.
A child is not ready to use a regular seat belt until:
- He/she is tall enough so that his/her legs bend at the knees against the edge of the seat.
- He/she is mature enough to remain seated with his/her back flat on the seat, not slouching.
- The lap belt sits high on the thighs or low on the hips, not on the stomach.
- The shoulder belt crosses the shoulder and chest, avoiding the arms and the neck.
A child ready to use an adult seat belt without the aid of a booster seat will be around 4 feet, 9 inches (about 1 1/2 meters) tall and roughly eight years old. Please keep in mind that, because children do vary in size by age, some children could still need a booster seat at the age of 10 or 11.