This paper describes the development of an interface system for attaching infant and child restraints and booster cushions to passenger vehicles. The resulting prototype, known as CANFIX is based on the ISOFIX concept which was conceived in Sweden. The CANFIX design comprises two rear attachments to be secured to two anchorage points located behind the vehicle seat bight. In forward-facing child restraints, the CANFIX system also includes the tether anchorage feature. The results of preliminary dynamic testing of three CANFIX modified restraint systems are presented in the paper with the results of tests to examine the compatibility of the CANFIX system with current vehicle seats.