摘要：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.
