The United States , the fourth largest country in the world by land area, has developed an extensive transportation system to serve its 300 million residents and 7 million business establishments. Americans travel extensively as they go to and from work, run errands and shop, transport children, visit their family and friends, take vacations, enjoy leisure time pursuits, and engage in other activities. U.S. businesses depend on the transportation system as they move their goods to markets here and abroad, set up supply chains and distribution networks, and send employees throughout the country and the world to conduct business. Trucks are the most widely used means of transporting freight in domestic transportation, but rail, water, and pipeline together account for a majority of ton-miles. Both passenger travel and freight shipments require an interconnected system of transportation modes to function effectively.