Besides imagining how a combination of alternative fuels and new vehicle technologies can help us meet GHG reduction targets, it is important to consider how transportation—particularly the light-duty sector—might make the transition to a low-carbon future. The light-duty vehicle (LDV) sector accounts for about two-thirds of energy use and greenhouse gas (GHG) emissions from transportation in the United States. Automakers are targeting light-duty markets for advanced electric-drive technologies such as plug-in hybrids and hydrogen fuel cell vehicles. In this chapter, we analyze and compare alternative scenarios for adoption of new LDV and fuel technologies that could enable deep cuts in gasoline consumption and GHG emissions by 2050. We also estimate the transitional costs for making new vehicle and fuel technologies economically competitive with gasoline vehicles. We do this with the caveat that concentrating only on the light-duty fleet may miss important constraints, especially for biofuels—which may be needed to make liquid fuels for air and marine transportation.