Many children progress from one type of restraint to the next at too small a size : should advice to parents be simple and based on child age, with variation in child size accommodated by overlaps in restraint specifications?

Published surveys of child in-vehicle restraint use demonstrate that many children are in an inappropriate type of restraint. In particular, children tend to progress from a forward-facing child restraint to a booster seat at too small a size, and from a booster seat to an adult belt at too small a size. Standards for child restraints are written in terms of their weight, not their age. In this paper, we explore what might be the consequences of very simple advice, such as: change the type of restraint at 6 months, 4 years, and 8 years. Obviously, children differ in size. This may be allowed for by writing the standard so that the restraint is suitable both for a small-for-age child at the youngest age and a large-for-age child at the oldest age. Our method uses the distribution of children’s weights at different ages. Given that, and given also the range of weights for which each restraint is appropriate, we work out how many children would be in an inappropriate restraint if progression were at particular ages. This turns out to be much less than the number observed under the current regime of weight-based advice. (a) For the covering entry of this conference, please see ITRD abstract no. E217713.