A smooth transition from a petroleum-driven transportation system to clean-burning automobiles with the performance and range of today＇s gasoline cars is plausible using high-efficiency hydrogen-fueled hybrid-electric vehicles. The introduction of hydrogen (H-2) vehicles will reduce U.S. dependence on oil imports, virtually eliminate automotive urban air pollution, accelerate the development of cost-effective renewable energy, and help stabilize greenhouse-gas emissions. Based on an economic and technical analysis, H-2 vehicles, when first introduced, can be cost-competitive with battery-powered electric vehicles. As market penetration increases, H-2-vehicle fueling costs would become competitive with the fueling costs of today＇s gasoline Vehicles (5 cent/mi). Hydrogen production at filling stations, vehicle fleets, and homes would circumvent many start-up issues and would use existing natural gas and/or electricity energy infrastructures to begin the transition towards a clean, flexible, sustainable, and secure transportation fuel.