Efficient movement of freight within the United States and across its borders is a critical enabler of future U.S. economic growth and competitiveness. Such efficiency is now threatened by capacity bottlenecks, inefficient use of some components of the freight infrastructure, interference with passenger transport, the system's vulnerability to disruption, and the need to address important emission and energy constraints. In this volume, the authors provide a broad overview of U.S. freight transportation, discuss its role in the supply chains of various types of businesses, and provide data about its capacity in relation to demand for goods movement. They conclude with a discussion of the need to modernize the freight-transportation system and the overarching issues this involves: increasing capacity through operational improvements and infrastructure enhancement, making the system more adaptable and less vulnerable to disruption, addressing the energy and environmental concerns associated with freight transportation, and building support for public and private investment in the system.