Why are people still dying in frontal crashes despite seat belt use, air bags, and the crashworthy structures of late-model vehicles? Statistical analyses show the combination of seat belt use and air bags is highly effective, reducing fatality risk by 61 percent compared to an unbelted occupant of a vehicle not equipped with air bags - but 61 percent is not 100 percent. To address the question, an interdisciplinary NHTSA team reviewed every case of a frontal fatality to a belted driver or right-front passenger in a model year 2000 or newer vehicle in the Crashworthiness Data System (CDS) of the National Automotive Sampling System through calendar year 2007. This work details the authors' findings.