Studies of child occupant safety in cars in have consistently reported that one of the biggest problems with unsafe use of child restraints is premature graduation of children into restraint systems that the intended for older children.

In 2007 our team conducted a study to identify ways of ensuring that children travel in the safest restraint for their age and size. The outcome of the review was subsequently included in revisions to Australian road rules.

During the study we identified the potential for the concept of a ‘safe ride height’ line. That is, the child restraint systems, and vehicles in which they travel, could both be clearly marked with a ‘safe ride height’ line to be used to indicate whether a child was an appropriate size for the restraint.

The ‘safe ride height’ line could be integrated prospectively and retrospectively across the full width of the seat back of the vehicle. If a child’s shoulders are below the line, the child is too small for an adult seatbelt.

In child restraints, the ‘safe ride height’ lines can be tailored for each type of restraint system. For example, in a forward facing child seat, there could be a lower ‘safe ride height’ line for a child who has just grown big enough, and an upper ‘safe ride height’ line for a child who now needs to graduate out of the restraint.

‘Safe ride height’ lines are included in the current draft for a revised Standard for child restraint systems in Australia.

What this paper offers that is new is the concept of a ‘safe ride height’ line that will provide an easy guide for carers as to the appropriate size restraint for a child and allow simple self evident enforcement of correct restraint usage rules.