DRAFT: A user-tailored tool for comparative cradle-to-grave environmental assessment of car retention versus replacement

This work presents the development of a novel tool to support environmentally informed decision-making in the automotive sector by comparing two competing scenarios: maintaining an existing vehicle versus replacing it with a new one. While economic decision-support tools exist for such choices, there remains a critical gap in evaluating the environmental consequences. The proposed tool addresses this by implementing a cradle-to-grave Life Cycle Assessment (LCA) framework, which includes greenhouse gas emissions from vehicle production, maintenance and repair, well-to-wheel fuel or electricity consumption, and end-of-life processes. Unlike existing approaches, the tool accounts for non-average cases and real-world usage patterns. It allows detailed customization based on vehicle segment, powertrain type, energy source, geographic context, and annual mileage. It also explicitly incorporates existing vehicles, for which production emissions are no longer attributable, and introduces a novel attribution method for sharing production and disposal impacts in cases of second-hand ownership or short lifespans. These features enable more accurate assessments of vehicle sustainability across diverse user profiles. The result is a flexible yet robust assessment platform that enables users and policymakers to quantify the environmental consequences of vehicle replacement strategies, providing critical insights into the role of vehicle longevity and individual usage patterns in sustainable mobility transitions.