Optimising product advice based on age when design criteria are based on weight: child restraints in vehicles

Abstract

The motivation for this paper is the high rate of inappropriate child restraint selection in cars that is apparent in published surveys of child restraint use and how the public health messages promoting child restraints might respond. Advice has increasingly been given solely according to the child's weight, while many parents do not know the weight of their children. A common objection to promoting restraint use based on the age of the child is the imprecision of such advice, given the variation in the size of children, but the magnitude of the misclassification such advice would produce has never been estimated. This paper presents a method for estimating the misclassification of children by weight, when advice is posed in terms of age, and applies it to detailed child growth data published by the Centers for Disease Control and Prevention. In Australia, guidelines instructing all parents to promote their children from an infant restraint to a forward-facing child seat at 6 months, and then to a belt-positioning booster at 4 years, would mean that 5% of all children under the age of 6 years would be using a restraint not suited to their weight. Coordination of aged-based advice and the weight ranges chosen for the Australian Standard on child restraints could reduce this level of misclassification to less than 1%. The general method developed may also be applied to other aspects of restraint design that are more directly relevant to good restraint fit.

Discordance between age- and size-based criteria of child passenger restraint appropriateness

“…It is also possible that parents have been responsive to newer child safety seat labels and instruction manuals that include messages about delaying transitions. Although age is commonly used as a proxy for size in discourse on child passenger restraint appropriateness, as it is a simpler characteristic to measure (Anderson et al 2009), the wide variation in child growth patterns (CDC 2000) supports a shift in focus to size for child passenger restraint selection. Helping families to understand when to make a size-appropriate restraint transition has the potential to increase the safety of individual child passengers.…”