Evaluating the impact of advanced vehicle and fuel technologies in U.S. light duty vehicle fleet

Abstract

The unrelenting increase in oil use by the U.S. light-duty vehicle (LDV) fleet presents an extremely challenging energy and environmental problem. A variety of propulsion technologies and fuels have the promise to reduce petroleum use and greenhouse gas (GHG) emissions from motor vehicles. Previous work in this domain has compared individual vehicle or fuel alternatives. The aim of this research was to deepen the understanding of the likely scale and timing of the fleet-wide impact of emerging technologies. A model of the light-duty vehicle fleet showed that fuel consumption of mainstream gasoline internal combustion engine (ICE) technology vehicles will determine the trajectory of fleet fuel use and GHG emissions over the next two decades. Using vehicle simulations and historical data, the trade-off between vehicle performance, size and fuel consumption was quantified. It was shown that up to 26 percent reduction in future LDV fuel use is possible with mainstream gasoline ICE vehicles alone if emphasis of vehicle technology is on reducing fuel consumption rather than improving performance. Addressing this vehicle performance-size-fuel consumption trade-off should be the priority for policymakers. By considering both supply and demand side constraints on building up vehicle production rates, three plausible scenarios of advanced vehicle market penetration were developed. Due to strong competition from mainstream gasoline vehicles and high initial cost, market penetration rates of diesels and gasoline hybrids in the U.S. are likely to be slow. As a result, diesels and gasoline hybrids have only a modest, though growing potential for reducing fleet fuel use before 2025. In general, the time-scales to impact of new technologies are twenty to twenty-five years.

(cont.) Integrating vehicle and fuel scenarios showed that measures which reduce greenhouse gas emissions also reduce petroleum consumption, but the converse is not necessarily true. Policy efforts therefore should be focused on measures that improve both energy security and carbon emissions at the same time. While up to 35 percent reduction in fleet GHG emissions from a No Change scenario is possible by 2035, the magnitude of changes required to achieve these reductions are daunting, as all of the current trends run counter to the changes required.