A case study was conducted of 123 crashes involving 144 fatally injured lap-shoulder belted front-seat occupants. The crashes occurred throughout the United States in 1985-86 and involved 97 driver and 47 right-front passenger deaths in new vehicles. A judgment was made by consensus of a safety panel on the potential for saving the victim's life by the addition of safety technology. Supplemental airbags provided the greatest potential for improving the life-saving effectiveness of current lap-shoulder belts. Overall, airbags may have prevented 12% of the belted occupant fatalities and 27% of the deaths in frontal crashes. The benefit of supplemental airbags was greater for the right-front passenger, in part, because of more females and occupants over 60 years of age in that seating position. A majority (68%) of the belted fatalities were judged unpreventable by reasonable restraint or vehicle modifications. This level is indicative of the extreme severity of many of the fatal crashes involving extensive vehicle damage and forces on the occupant compartment, unusual crash configurations and causes of death, and unique situations related to seating position and crash dynamics. Using published levels of belt effectiveness, 50% of all fatalities may not be preventable by the use of lap-shoulder belts, supplemental airbags, and practicable changes in crashworthiness systems. The study addressed only the potential benefit of supplemental-restraint components and airbags and did not consider possible adverse effects which might occur in real-world crashes.