There is debate about the appropriate design of supplementary airbags for passenger car occupants with high levels of seatbelt use. A theoretical analysis was performed to demonstrate the likely costs and benefits of U.S. fullsize driver airbags and the smaller European-style facebag. This study, undertaken for the Federal Office of Road Safety in Australia, builds upon previous work in this area. Benefits were determined using Harm Reductions for front-seat occupants involved in frontal crashes. A sensitivity analysis was undertaken for different benefit scenarios for the facebag, given the lack of available performance data. Likely costs of the components were derived from information provided by the local automobile manufacturers, part suppliers, and vehicle importers, with adjustments made for fitting to Australian vehicles. The results demonstrate the advantage of fullsize airbags over facebags, even when seatbelt wearing rates are high.