Thirteen of 41 booster car seats were deemed “poor” at protecting kids, according to a new report from the Insurance Institute for Highway Safety.

In a study with the University of Michigan Transportation Research Institute, the IIHS evaluated how 41 booster car seats helped improve belt fit for kids. The key to any booster car seat working effectively is belt fit: making sure the lap belt fits across the child’s hip . . . and the shoulder belt fits across the center of the shoulder (not too low or high on the neck).

Here’s the bottom line from the report:

Not Recommended

  • Safety Angel Ride Ryte backless
  • Cosco/Dorel (Eddie Bauer) Summit
  • Graco CarGo Zephyr
  • Evenflo Big Kid Confidence
  • Cosco/Dorel Traveler
  • Compass B505
  • Compass B510
  • Evenflo Generations
  • Dorel/Safety 1st (Eddie Bauer) Prospect
  • Cosco Highback Booster
  • Cosco/Dorel Alpha Omega
  • Evenflo Chase Comfort Touch
  • Safety 1st/Dorel Intera

Best Bets

  • Graco TurboBooster backless with clip
  • Fisher-Price Safe Voyage backless with clip
  • Combi Kobuk backless with clip
  • Fisher-Price Safe Voyage
  • Britax Parkway
  • LaRoche Bros. Teddy Bear
  • Safeguard Go backless with clip
  • Volvo booster cushion
  • Recaro Young Style
  • Britax Monarch

Good Bets

  • Graco TurboBooster
  • Safety Angel Ride Ryte
  • Recaro Young Sport
  • Combi Kobuk
  • Safety 1st/Dorel Apex 65

Our analysis: We were impressed with the thoroughness of the report (read the press release summary here; see pictures of good fit and bad fit). For example, the study evaluated the booster seats in “seven conditions spanning a range of belt positions measured in 31 vehicle rear seats.”

We liked the transparency of the research—we’ve met with the folks at the University of Michigan Transportation Research Institute (UMTRI) in the past year and toured their facility. We were impressed with their professionalism and commitment to child passenger safety. Note how many seats they evaluated (41), representing all the types of boosters (combo, highbacks, backless, etc).

Comments on our recommendations and this report:in our most recent book, we recommended the Cosco/Safety 1st Summit as a good harness seat. We will revise that based on this report (which said the Summit was not recommended). Unfortunately, the report did not evaluate the Graco Nautilus, which we also recommend.

Our top picks for belt-positioning boosters faired well: the Graco TurboBooster was named a “good bet” as a high back booster and “best bet” as a backless booster. We also liked the Britax Parkway, which was named a “best bet.” The only loser was our runner-up pick of the Compass B510, which was “not recommended” by the report—we will update our recommendations to reflect this.

Note that many of the not recommended seats were combo seats that work with a five-point harness and then convert to a highback booster. Other combos are birth to boosters like the Cosco Alpha Omega. We have long criticized this seat (which is pitched as the only car seat you’ll ever need, from infant to convertible to booster). This report confirms our research that it does not work well as a booster.

We imagine that this report may hasten the demise of combo seats like the Graco CarGo and Evenflo Generations—most of the new car seats are five-point harnesss seats that work up to 65 pounds (the Britax Frontier, Graco Nautilus). We wonder if the market may move toward these high weight harness seats—and simple backless boosters like the Graco TurboBooster (backless) for older kids.

Meanwhile, the discussion on this report continues on our message boards. And you can always post your comments below!