Incorrect use of child restraints is a longstanding and widespread problem that triples the risk of injury to children in car crashes and has proved intractable to existing interventions Currently one in two children travelling in cars incorrectly use their restraint. Using cutting edge naturalistic and epidemiological studies in an innovative mix, this project will (i) characterise child restraint design features important for minimising errors related to the real world interaction between restraint design, parents and children, and (ii) determine the effectiveness of using optimally designed restraints. This research will deliver the first comprehensive understanding of how a child restraint can be designed to minimise incorrect use.