Most parents know about the importance of car seats for infants and toddlers, but booster seats for older kids are often required by law, too -- yet a new survey finds lots of carpooling moms and dads use them inconsistently at best.

In the national survey, researchers from the University of Michigan asked 681 parents about their use of booster seats. Among them, 64 percent reported carpooling with children.

Those parents said they use a booster seat three-quarters of the time when driving their own children in the family car, but only half said their child always uses a booster seat when riding with friends who do not use booster seats.

In addition, the survey, published online January 30 in the journal Pediatrics, found one in five parents doesn't always ask other parents to use a booster seat for their child.

"We found that they were using booster seats less often for their own children, and they were also less likely to ask another parent to use a booster seat for their child," said study co-author Dr. Michelle Macy, a lecturer in the Department of Emergency Medicine and Pediatrics at the University of Michigan.

She added that national guidelines suggest using booster seats for children under four feet, nine inches tall, the height of an average 11-year-old, but even the states with booster seat regulations don't specify height as the basis of their laws. "Most of the state laws are set [so parents] use a booster seat until the child is eight," she said.

For carpooling parents, the hassle involved with moving a booster seat from one car to another could lessen their use, so Dr. Macy suggests researchers work with safety-seat or automobile manufacturers "to see if they can come up with some options that would be more portable for families."

But inconvenience aside, booster seats should always be used. "We've come a long way, and the injuries and deaths have really gone down," she said. "[Parents] should really consider the importance of being consistent with the way they're approaching safety with their kids, and not let [booster seats] become a point of conversation or compromise."

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