As the price of natural resources and the threat of climate change continue to rise, advancements for cheaper, cleaner, and more efficient power are being made for vehicle use, leading to a wealth of different fuel and powertrain choices for advanced-technology vehicles. Potential alternative fuel pathways include biofuels, electric and hydrogen. Likewise, there are numerous platforms for alternative powertrains, e.g., all-electric, hybrid, plug-in hybrid. There have been numerous efforts by researchers to evaluate different pathways and platforms [1-4]. Federal agencies have also developed useful tools, e.g., GREET [5] and MOVES [6] as well as databases, e.g., National Transportation Study [7] to assist in these efforts. Various factors will affect the development of alternative fuel passenger vehicles, including technical advancements, costs of fuel sources, development of infrastructure, policy decisions, and consumer acceptance. These factors make it difficult to predict the long term future of vehicle power trains. However, plug-in hybrid electric vehicles (PHEV) are well positioned to be widely adopted in the near future. They have an obvious path to market as they do not require significant infrastructure investments, will likely be cost-effective in the near term, and adoption would make meaningful greenhouse gas emission reductions. Nearly all major automobile manufacturers have either introduced PHEV, or have announced that such vehicles are under development. An EPRI study [8] evaluated potential implications of greenhouse gas (GHG) reductions, and considered low, medium and high market penetration for PHEV. The medium penetration model assumed approximately 35% PHEV by the year 2020. While these vehicles hold promise for reducing the emission of GHG, particularly in light of an electric grid that is becoming cleaner, there is also developing concern that widespread adoption of PHEV will adversely affect state gasoline tax revenues. A sound understanding of these tradeoffs is required to develop rational local policies regarding plug-in hybrid electric vehicles.