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.

Keywords:

• child restraint systems
• standards
• public information programmes
• evaluation and assessment

Acknowledgements

There is overlap between this paper and presentations given at three conferences during 2007 (listed in the References as Anderson and Hutchinson 2007a,b, Anderson et al. 2007). We are grateful for helpful comments from participants in those conferences and others with whom we have discussed this work. The Centre for Automotive Safety Research receives core funding from the Motor Accident Commission of South Australia and the South Australian Department for Transport, Energy and Infrastructure. The views expressed in this paper are those of the authors and do not necessarily represent those of the sponsoring organisations or the University of Adelaide.