This primer is an introduction to the issue of climate
change and its implications for transportation
policy in the United States. The paper is organized
in five parts:
Part I summarizes the current state of scientific
knowledge concerning the causes and impacts of climate
change. This section reviews the data that shows
climate change is occurring; summarizes the impacts of
climate change, including impacts on the transportation
system; and explains how greenhouse gas emissions contribute
to climate change.
Part II provides an introduction to climate change policy
issues. This section briefly outlines the main goals of
climate change policies, and provides an overview of the
major strategies that are being considered and/or adopted
to achieve those goals. This section includes a discussion
of “cap and trade” proposals, a carbon tax, energy efficiency
standards, and other economy-wide proposals that
could be adopted to address climate change.
Part III discusses trends in GHG emissions from road
transportation. This section reviews historical trends and
current government projections for fuel economy, vehicle
miles traveled (VMT), and greenhouse gas emissions
from road transportation. It also presents four alternate
scenarios showing that faster improvements in fuel economy
and somewhat slower growth in VMT could result
in steep reductions in greenhouse gas emissions by 2050.
Part IV reviews potential measures to reduce GHG
emissions from road transportation. This section discusses
potential improvements in vehicles and fuels;
potential ways to reduce the growth of VMT; and
potential operational strategies for reducing GHG
emissions. This section then provides an overview of
policy tools that could help promote these changes,
including measures such as increasing fuel economy
standards; requiring greater use of renewable fuels;
expanding funding for research and development;
and establishing a “carbon price” through a cap-andtrade
system or other measures.
Part V identifies issues for further research. This section
lists a series of issues that warrant additional research by
AASHTO or others. For example, one important issue
is the underlying growth trend in VMT. There is some
evidence that growth in VMT is slowing due to economic
and demographic factors. Additional research is needed
to ensure that policymakers have a solid basis for setting
policies on transportation and climate change.
The Reference Materials section, which follows Part
V, includes a list of major studies and other published
reports on climate change and transportation. A literature
review summarizing these reports has been posted
on the AASHTO web site along with this primer at
bookstore.transportation.org.
This primer is based on the most recent research in the
field. Its purpose is to outline the current thinking of governmental
agencies, researchers, and advocacy groups on
the issue of climate change and transportation. The conclusions
stated in those reports do not necessarily reflect
the views of AASHTO or its members. AASHTO will
be sponsoring additional research and will be providing
the results of that research in subsequent reports.