The program objective was to develop an effective inflatable occupant restraint system for unbelted rear seat occupants of motor vehicles. An extensive series of developmental and evaluative impact sled tests included variations in occupant position and size using a standard-size American sedan as the basic vehicle for incorporation of the passive restraint.The restraint system includes a crushable honeycomb knee bar to limit femur loads and to control the head and upper torso trajectory of the unbelted occupants. At speeds below which the airbag deploys, protection is provided by energy-absorbing padding on a head bar as well as on the knee bar. For high-speed crashes, the airbag deploys, and the bag loads are carried out through the head bar and the knee bar support plate. Nondeployed protection is provided for crash speed pulses up to approximately 20 mph in order to satisfy multiple impact considerations, and nonvented side bags are used for oblique impact protection.In terms of present injury criteria, the restraint was effective for the 50th percentile adult for crash speeds up to 45 mph for frontal and 30 deg oblique sled simulated barrier crashes. A performance envelope of crash speed at which protection is provided for other dummy sizes and positions was obtained.