This primer is intended to provide AASHTO members with an introduction to the issue of climate change and its implications for transportation policy in the United States. This primer is based on the most recent research in the field. Its purpose is to outline for AASHTO members 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.