Development of dramatically lightweight and fuel-efficient vehicles has been slowed by perceptions that lighter vehicles are less safe. Highly safe lightweight vehicles may seem counterintuitive. Yet, size need not determine the weight of a vehicle and vehicle safety is primarily a function of design. RMI virtually modeled an ultralight concept vehicle that met NHTSA safety requirements in crash simulations. It also performed well in side impact testing and had a low likelihood of rollovers. In car-to-car crash simulations, the concept vehicle performed below that of a production Ford Edge. Minor design changes improved its test performance significantly, demonstrating the potential for dramatic safety improvements in a production-intent design. The ultralight concept was also less “aggressive,” indicating that a 100 percent lightweight fleet would increase overall safety. First lightweighting the heaviest vehicles in today’s fleet would accelerate progress toward “Triple Safety”—protection from climate change, drivers themselves, and other road users.