Electrification, Lightweighting, and Materials Supply: A Dynamic Life Cycle Assessment of the U.S. Light-Duty Vehicle Fleet

Abstract Electrification and lightweighting are reshaping vehicle designs and materials demand, with uncertain net effects on life cycle greenhouse gas (GHG) emissions. Most existing fleet studies treat material choices, materials markets, and vehicle adoption separately, without capturing feedbacks between design, supply chains, and consumer behavior. This study develops an integrated system dynamics–life cycle assessment (SD–LCA) framework to explore these interactions for the U.S. light-duty vehicle fleet from 2000 to 2060. The model extends an established powertrain diffusion framework by endogenizing vehicle body material selection, battery capacity evolution, and materials market responses, linking these dynamics to a bottom-up life cycle assessment of fleet GHG emissions. Scenario analysis shows that increasing aluminum use in lightweight gasoline vehicles improves their utility and market share, largely offsetting use-phase GHG savings and yielding only modest reductions in total fleet emissions. In contrast, faster battery electric vehicle adoption raises cradle-to-gate emissions but more than compensates through lower use-phase emissions, reducing total fleet GHGs. Shifts in vehicle material demand also generate transient imbalances in steel and aluminum markets, temporarily lowering recycled fraction and increasing cradle-to-gate emissions. The SD–LCA framework demonstrates how feedbacks between vehicle design, materials supply, and consumer adoption shape fleet decarbonization pathways.