Booster seats

Last—but not least—for child safety

Last reviewed: July 2011
Booster seats position kids in belts meant for adults
Booster seats position kids in belts meant for adults.

Once your child puts diapers, strollers, and other trappings of babyhood behind him, you might think it’s time to move on from car seats, too. Not so. Young children grow rapidly, so it’s tempting to think that they can graduate from a car seat to a vehicle seat and safety belt like a “big” kid. But doing so would compromise their safety. The solution: booster seats.

A booster seat raises a child’s body enough to allow a vehicle’s three-point belt—designed to protect an average-sized adult—to keep him safe. You might also hear them referred to as belt-positioning boosters because their job is to properly position a child in a seat.  Some boosters look like large, square pillows. These are called backless boosters—think sitting on a phonebook to reach the dinner table. There are also high-back models and those that can be used in either high-back or backless mode. We tested all three types. (Subscribers can see our belt-positioning booster seat Ratings.) Another variation is called a toddler booster or combination seat. They have their own five-point harness that can be used for children who are too young for boosters. The harness can then be removed when your child is ready to use it in booster mode. See our toddler boosters report for more information.

Our tests found performance differences among types and models, and even among seats that fit well initially but didn’t maintain a good fit with a squirming child, all of which can affect child safety. Overall, our tests found that high-back models had the best belt fit, followed by boosters that convert from high-back to backless (which are best when used with the back), and finally backless boosters. But any booster seat appears to be safer than none at all for children shorter than 4’9” (the height of an average 11-year-old). Most vehicle belts won’t fit a child under that height without a booster. The most recent research also shows that children between 4 and 8 years old are 45 percent less likely to sustain injuries when riding in booster seats vs. those using a vehicle’s safety belts alone. But using a booster seat is the safest way for any child up to 4’9” to travel, regardless of age. Injuries sustained by children using safety belts alone can be life-threatening, including abdominal bruising, internal organ damage, and lumbar-spine injuries, to name a few.

Seven-year-old without a booster. The shoulder portion of the seatbelt is too close to his neck. The lap portion of the belt is lying across his abdomen, not his upper thighs and hips. And his knees are not able to bend comfortably over the edge of the seat, so he may slouch, which can worsen seatbelt fit if the lap belt moves further up onto his abdomen.

Belt-positioning boosters are a safe choice, but children are safest in a car seat with its own five-point harness (either a convertible car seat or a harnessed toddler-booster) in the back seat of your car. So don’t be in a rush to have your child graduate to a booster seat too soon. Many of them have a minimum weight requirement as low as 30 pounds. Some 15-month-olds weigh that much, but we don’t consider it safe for children that young to ride in any seat that doesn’t include a harness.

After a child reaches the height or weight limits of a harnessed seat (some accommodate kids as tall as 50 inches and weighing up to 90 pounds), he can start using a belt-positioning booster without a harness, which adapts a vehicle’s seatbelts—meant to accommodate an average-sized adult—to fit a child’s smaller frame. A belt-positioning booster can be the last car seat a child uses before he starts using the vehicle’s seat—when he’s around 4’9” tall and the safety belt fits him correctly—which is normally at around age 8 at the earliest, as recommended by a 2009 study in the journal Pediatrics.

When to move on: The 5-step test

When can your child sit on a vehicle seat without the need for a booster? When you can answer "yes" to all these questions:

  • Does your child sit all the way back against the vehicle seat?
  • Do your child's knees bend comfortably at the edge of the vehicle seat?
  • Does the vehicle belt cross your child's shoulder evenly between the neck and arm?
  • Is the lap belt as low on the abdomen as possible, near the top of the thighs?
  • Can your child stay comfortably seated like this for the whole trip?

And don't forget to check the laws in your state to find out the requirements governing child passenger restraint use where you live in table or map format.