Comprehensive life-cycle greenhouse gas emissions rating for different vehicle types with lightweight materials

Abstract

Sustainable transportation is fundamental to addressing the challenges of climate change, and accurately measuring emissions beyond the tailpipe is essential for understanding a vehicle's true environmental impact. Limiting analysis to the use phase can be misleading, as production, fuel cycle, and end-of-life stages also contribute significantly. This study develops a cradle-to-grave greenhouse gas (GHG) rating for light-duty vehicles that combines rigorous life-cycle assessment (LCA) with a simple, consumer-oriented scale. We evaluate four powertrain types, internal combustion engine vehicles (ICEVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs) and battery electric vehicles (BEVs) and six material configurations (baseline steel, advanced high-strength steel, aluminium, magnesium, glass-fibre reinforced plastic and carbon-fibre reinforced plastic) in the body-in-white. Baseline cradle-to-grave emissions are 423, 270, 279 and 186 gCO2eq/mile for ICEV, HEV, PHEV and BEV, corresponding to 34–56% reductions for electrified powertrains relative to the conventional vehicle. Substituting lightweight material in the body-in-white reduces life-cycle emissions by up to 14% for ICEVs and about 6–10% for electrified vehicles. Electricity mix strongly affects BEV performance: under low-carbon grids BEVs clearly dominate, whereas under carbon-intensive grids efficient HEVs can approach or surpass BEVs. Mapping LCA results onto both a strict EPA-aligned 1–10 GHG rating and a supplementary life-cycle-calibrated rating shows that tailpipe-only metrics overrate PHEVs and BEVs and underrate ICEVs and HEVs. The paper demonstrates that electrification and lightweighting are complementary strategies and that a holistic rating provides clearer guidance for consumers and policymakers.