Travel behavior is undergoing a period of significant change in the United States, and this change is beginning to reveal itself in long-standing measures of transportation. While the United States is still heavily dependent on the personal automobile for mobility, changes in technology, demographics, economics, and attitudes are transforming how mobility is attained. At the same time, advances in information technology are opening new ways for transportation activity to be measured more comprehensively. These transformative trends are reshaping how we think about transportation policy,...