Minimum weight limits on some booster seats may put a child at risk

There's a reason that safety experts recommend keeping your child in an age-appropriate child restraint as long as possible before graduating to the next type. Moving the youngster to a less restrictive car seat too soon can be a step backward in terms of safety. This is especially true with booster seats that can be used with the car's three-point seat belt rather than a harness. In Consumer Reports recent tests of booster seats, we found that 80 percent of manufacturers suggest a weight limit typical of a child well under three, which is too young for a booster seat.

In our recent review of booster seats, we found a disconnect between the minimum weight limits allowed by manufacturers and what we would consider best practice for booster use. Of the 34 booster seat models in our tests, 28 state a minimum allowable weight of between 30 and 33 pounds. Current growth charts, however, show that the average 30-pound child is about two-and-a-half years old, far too young to move a child out of a seat with a harness, according to our safety experts.

Even greater cause for concern is that a large child of 15 months who is in the 95th percentile for weight can easily approach 30 pounds. At that age a child's body is not developed enough nor likely to be tall enough for this type of seat.

A good thing is that of the 28 booster seats with the lower allowable weight limits, at least half also include a minimum age limit of three and others include height limits that are more typical of a three-year-old. These added age or height limitations help but three is still too young for opting out of the added protection of a harnessed seat. A child this age is usually not mature enough for the freedom of movement a booster seat allows and can pose a distraction to the driver. We also found two seats that indicate they can be used by a child starting at age one. Lets be clear, a booster is not the seat for any one-year-old.

Six seats had the more reasonable minimum weight limit of 40 pounds. This makes sense because the growth of children between 30 and 40 pounds occurs at a slower rate than when they are infants. An average 40-pound child is typically closer to age five, a much safer age to consider making a transition to booster use. And many booster seats that can be used in both a highback and backless configuration have a higher minimum weight limit of 40 pounds when used in the backless mode. But for the best belt fit, we still prefer a highback booster.

Even though many children may balk at staying in a harnessed car seat, our safety experts recommend that they remain harnessed as long as possible. A five-point-harness is far more secure than a car seat belt meant for an adult. Most harnessed seats can accommodate children as heavy as 65 pounds and some can grow with a child up to 90 pounds. In the event of an accident, it's the safest option.

In our tests of booster seats, three highback boosters, four backless boosters and five seats that convert from a highback to a backless offer the best balance of value and overall performance. We test crash protection, ease-of-use and the ability to provide a proper belt fit in each mode. The convertible Evenflo Big Kid Sport, $30, and the similar Evenflo Big Kid Amp Highback, $40, were the only seats to score excellent for their ability to combine crash protection and best fit in their highback mode but they were only average in the backless mode. For more on how to fit a car seat to a growing child, read our car seat buying guide.