摘要：The state of California is expected to have significant population growth in the next
half-century resulting in additional passenger transportation demand. Planning for a
high-speed rail system connecting San Diego, Los Angeles, San Francisco, and Sacramento
as well as many population centers between is now underway. The considerable investment
in California high-speed rail has been debated for some time and now includes the
energy and environmental tradeoffs. The per-trip energy consumption, greenhouse
gas emissions, and other emissions are often compared against the alternatives
(automobiles, heavy rail, and aircraft), but typically only considering vehicle
operation. An environmental life-cycle assessment of the four modes was created to
compare both direct effects of vehicle operation and indirect effects from vehicle,
infrastructure, and fuel components. Energy consumption, greenhouse gas emissions, and
SO2, CO,
NOX, VOC,
and PM10 emissions were evaluated. The energy and emission intensities of each mode were normalized
per passenger kilometer traveled by using high and low occupancies to illustrate the range
in modal environmental performance at potential ridership levels. While high-speed rail has
the potential to be the lowest energy consumer and greenhouse gas emitter, appropriate
planning and continued investment would be needed to ensure sustained high occupancy.
The time to environmental payback is discussed highlighting the ridership conditions where
high-speed rail will or will not produce fewer environmental burdens than existing
modes. Furthermore, environmental tradeoffs may occur. High-speed rail may lower
energy consumption and greenhouse gas emissions per trip but can create more
SO2 emissions (given the current electricity mix) leading to environmental acidification and
human health issues. The significance of life-cycle inventorying is discussed as well as the
potential of increasing occupancy on mass transit modes.
