IIHS Rates Booster Seats; New Study Examines Effectiveness
Reprinted from The Safety Record, Volume 6, Issue 6, December 2009
ARLINGTON, VA — The Insurance Institute for Highway Safety released its latest ratings for boosters, and out of 60 models gave 15 models high marks and dinged 11 as “not recommended.” Meanwhile, a statistical analysis of the association between booster seat use and the risk of death found that boosters were no better than seatbelts alone in preventing death among 4-8-year-old children.
Researchers T.M. Rice, C.L. Anderson, and A.S. Lee of the University of California, Berkley’s Traffic Safety Center and the Center for Trauma and Injury Prevention Research at the University of California Irvine’s Department of Emergency Medicine conducted a matched cohort study (matching exposed to unexposed persons prior to outcome determination) using 1996-2006 data from the Fatality Analysis Reporting System. The sample of 6,006 vehicles included those with two or more occupants in the first two rows of seating, with one or more occupants aged 4-8 years old in which one or more occupants died.
The analysis, published in Injury Prevention, showed that seat belts, used with booster seats, were “highly effective” in preventing death among young motor vehicle occupants. In a severe crash, unrestrained children in the sample were 2.8 times more likely to die than those restrained in seat belts with boosters. The effectiveness for children 6-8 years was slightly less. But the study showed that belts alone were almost as effective: “Unrestrained children were 2.6 times more likely to suffer fatal injury than belted children. The estimated death risk ratio comparing seatbelts with boosters with seatbelts alone was 0.92.”
The researchers concluded that, in looking at the risk of death only, “booster seats do not appear to improve the performance of seatbelts.” They also noted that these results were similar to a 2002 study published in the Annual Proceedings Association for the Advancement of Automotive Medicine.
The numbers did not lead the researchers to recommend that young children use seatbelts alone because other studies show that booster seats reduce non-fatal injury severity – the abdominal and spinal injuries characteristic of seatbelt syndrome.
“Clinicians and injury prevention specialists should continue to recommend the use of boosters to parents of young children,” the study’s authors said.
IIHS’s second annual recommended booster seat list attempts to help parents and caregivers select the booster seats “most likely to provide good lap and shoulder belt fit in a range of vehicles,” the institute said in a news release about rankings. In its first year, the institute evaluated 41 seats. This latest round covers nearly all models sold in the United States. Eventually, IIHS plans to structure its booster seat ratings like its Top Safety Pick awards, evaluating new models as they are released to the public.
Institute engineers assess each model by measuring how lap shoulder belts fit a “specially outfitted” 6-year-old crash test dummy under “four conditions spanning the range of safety belt configurations in vehicle models. Each booster gets four scores for lap belt fit and four for shoulder belt fit. The overall rating for each booster is based on the range of scores for each measurement,” the news release said.
The IIHS’s best-rated boosters are: the Combi Dakota backless with clip, Recaro Young Sport highback (combination seat), Recaro Vivo highback, Maxi-Cosi Rodi XR dual-use highback, Evenflo Big Kid Amp backless with clip, Eddie Bauer Auto Booster dual-use highback, Cosco Juvenile Pronto dual-use highback, Britax Frontier highback.
The Institute did not recommend: Harmony Secure Comfort Deluxe backless with clip, Combi Kobuk dual-use highback, Evenflo Express highback (combination), Eddie Bauer Deluxe highback (combination), and Evenflo Sightseer highback. Also on the list are 3-in-1s including the Safety 1st Alpha Omega Elite, Alpha Omega Elite, Eddie Bauer Deluxe 3-in-1, Safety 1st All-in-One, Alpha Omega Luxe Echelon, and Alpha Omega.
Half of the boosters that aren’t recommended are 3-in-1s that leave the lap belt too high on the abdomen and the shoulder belt too far out on the shoulder. One seat, the Harmony Secure, has armrests that push the lap belt away from the hips, way out on a child’s thighs. Shoulder belt fit is the main problem for the rest — the Combi, 2 Evenflos, and the Eddie Bauer Deluxe.
Dorel Juvenile Group, the largest US children’s gear distributor, makes three of the most highly recommended boosters and seven of those that aren’t recommended. Dorel seats sell under the names Cosco, Dorel, Eddie Bauer, Maxi-Cosi, and Safety 1st.
These recent developments contradict, in part, earlier findings by researcher Suzanne Tylko of Transport Canada, who reported three years ago that a five-point restraint system is the safest option for children.
Transport Canada measured the performance of booster seats with child Hybrid III dummies representing a 10- and 6-year-olds in full frontal rigid barrier and frontal offset deformable barrier tests. The 6-year-old dummy was restrained in a belt-positioning booster and the 10-year-old was restrained with either a booster or a three-point belt. Tylko and her colleague Dainius Dalmotas tested 77 passenger cars, cross-over vehicles, minivans and SUVs from the 2003-2005 model years, paired with low-back and high-back boosters, high-back boosters with a harness latch and tether and a lap and shoulder belt.
In the tests involving the six-year-old dummy in a lap and shoulder belt, the belt would either slide up into the neck or down to the shoulder, as the dummy pitched forward. In the latter case, some dummies rolled out of the belt entirely—particularly if there was any offset component to the crash—causing the head and chest to hit its lower extremities. Tylko found little difference among booster seats. All of them – unlike three-point belts alone – effectively kept the lap portion of the belt in the pelvic region, and prevented it from traveling into the abdominal cavity. But boosters didn’t do much to protect the child’s chest region, failing to keep them properly positioned in an adult three-point belt.