Environmental assessment of passenger transportation should include infrastructure and supply chains

TLDR

Decision makers must consider life‑cycle energy use and emissions, not just tailpipe data, to mitigate transportation’s environmental impacts. The study aims to provide a comprehensive life‑cycle inventory of energy, greenhouse gas, and selected air pollutant emissions for automobiles, buses, trains, and airplanes in the US. The inventory includes vehicle, infrastructure, fuel production, and supply chain components across these modes. The life‑cycle analysis shows that total energy inputs and greenhouse gas emissions exceed vehicle tailpipe values by 63 % for on‑road, 155 % for rail, and 31 % for air, with non‑operational components often dominating air pollutant emissions, which can be 1.1 to 800 times higher than operation and vary with passenger occupancy.

Abstract

To appropriately mitigate environmental impacts from transportation, it is necessary for decision makers to consider the life-cycle energy use and emissions. Most current decision-making relies on analysis at the tailpipe, ignoring vehicle production, infrastructure provision, and fuel production required for support. We present results of a comprehensive life-cycle energy, greenhouse gas emissions, and selected criteria air pollutant emissions inventory for automobiles, buses, trains, and airplanes in the US, including vehicles, infrastructure, fuel production, and supply chains. We find that total life-cycle energy inputs and greenhouse gas emissions contribute an additional 63% for onroad, 155% for rail, and 31% for air systems over vehicle tailpipe operation. Inventorying criteria air pollutants shows that vehicle non-operational components often dominate total emissions. Life-cycle criteria air pollutant emissions are between 1.1 and 800 times larger than vehicle operation. Ranges in passenger occupancy can easily change the relative performance of modes.