The ability of our nation's transportation system to provide for and maintain the efficient movement of freight is important to the continuing economic health of the United States. U.S. domestic freight tonnage is anticipated to approximately double -- and international freight tonnage expected to nearly triple -- by 2035. This book provides facts and figures on the flow of U.S. freight while examining the physical network, economic conditions and transportation system responsible for the movement of freight. It then explores the growing need to find new ways to address air quality concerns and greenhouse gas emissions associated with freight movements.