This study describes the incorrect use of child restraints among car drivers with young children and examines factors that may influence their misuse. A cross-sectional survey was undertaken in supermarket car parks with car drivers travelling with children under the age of 8 years. The main measure was errors in child restraint use. Short interviews were conducted with 1113 drivers with a close inspection of the child restraints used in the vehicles. Only 4% of children were unrestrained but 64% of drivers made at least one error in restraint use. Most respondents thought using a restraint was easy, but 65% of these drivers made at least one error. Child restraints are used, but many are incorrectly fitted and/or have the child incorrectly placed in them. Correct use is a moderately complex task. Restraint systems need to be designed to minimize the opportunity for error and maximize safety.