This brief is the first in a series that constitutes a body of knowledge describing commuting in America. Sponsored by AASHTO and carried out in conjunction with a National Cooperative Highway Research Program (NCHRP) project that provided supporting data, this body of work builds on three prior documents covering this topic that were issued over the past three decades. Unlike the prior reports, which were single volumes, this effort consists of a series of briefs, each of which addresses a critical aspect of commuting in America. Taken together, they comprise a comprehensive summary of American commuting. The briefs are disseminated through the AASHTO website. Accompanying data tables and an Executive Summary complete the body of information known as CIA 2013.