Car Seat Rule #5: Booster Seats and Seat Belts

This is the fifth in my Car Seat Rules series, in which I focus on one aspect of car seat use in a small, digestible article.

See other Car Seat Rules articles here:Rule #1, on the Chest ClipRule #2, on Rear-FacingRule #3, on NewbornsRule #4, on Front-Facing

*The advice given in the Car Seat Rules articles is not a substitute for having your seats checked by a car seat professional (CPST) or for reading the manual that came with your car seat.--------------------------

A five-point harness is safer than a seat belt as long as it fits properly. Once your child outgrows his front-facing car seat by height OR weight, it may be time to switch to a booster seat. Please check your state laws with regard to the minimum age and weight requirements for use of a booster seat, but the recommendation is typically at least four years old and at least 40 pounds.

A booster seat works differently from a car seat. A car seat is attached to the car using LATCH or seat belt, and then the straps of the car seat hold your child in place. A booster seat is not secured to the car (typically, although some models allow you to use the LATCH connectors to hold the booster in place) but merely helps to position your child so that the seat belt will fit him properly. The seat belt is then the primary restraint, just as it is for the adult occupants of the car.

Your child has outgrown his forward-facing seat when ONE of the following is true:

• He has reached the maximum weight limit of the harness,
• His ears are above the top of the car seat, OR
• His shoulders are above the top harness slot.

Your child is ready for a booster when ALL of the following are true:

• He has reached the minimum weight and age limits designated by your state's laws,
• When sitting in the booster, the shoulder belt falls across his collarbone, not his neck,
• When sitting in the booster, the lap belt sits flat against the tops of his thighs, not across his abdomen,
• He can sit upright in the seat through the entire trip and not lean over, slouch, or fall forward (otherwise the seat belt will not function properly), AND
• You trust that he won't unbuckle the seat belt while the car is in motion.

There are two basic types of booster seats, the HIGH-BACK BOOSTER and the BACKLESS booster. Their function is the same, and one has not been proven to be "safer" than the other. The basic difference is that a high-back booster helps to better position the shoulder belt, may provide some additional side impact protection, and helps to protect the head and neck if your car's seats don't have headrests. A backless booster positions only the lap belt, so you need to make sure your child is tall enough that the shoulder belt falls over his shoulder correctly.

Some boosters come with additional features which may interest you, such as a reading light, cup holder, or LATCH connectors. The LATCH connectors do not serve as restraints. Rather, they ensure that the booster seat does not become a projectile in the car if no one is sitting in the seat. (If your booster does not have LATCH connectors, you should buckle it in even when no one is using it.)

It is important to use a booster seat until your child is tall enough for the seat belt to fit properly without it. An ill-fitting seat belt can do more harm than good in a crash by causing internal injuries. Some states have implemented a minimum age or height before a child is no longer legally required to use a booster. In California and a few other states, a child must be eight years old OR 4'9" before using a seat belt without a booster.