The United States (US) freight transportation is a multimodal system that offers a range of competitive and complementary services. Five modes, including trucks, rail, water, air, and pipelines provide a variety of options with intermodal services often tying the options together. The various modes and intermodal services offer advantages and disadvantages in terms of price, speed, reliability, accessibility, visibility, security, and safety. Differences in service characteristics, costs, and prices result in shippers choosing particular modes, while transportation providers target particular markets and commodities. “As a result, truck and air modes are typically used for higher-value, lower-weight, and more time-sensitive freight, while rail and water freight transportation usually serve lower-value, heavier weight, and less time-sensitive shipments” (Brogan et al. 2013). Table 1 illustrates the potential advantages of different modes with respect to the weight of the commodities and distance traveled. The United States Department of Transportation and Federal Railroad Administration (2010) report ranked the various modes of transport in each of the cells by their comparative efficiency. Table 1 shows that rail or waterways are mainly used for bulk or heavy cargo that needs to transported for more than 500 iles. For lightweight cargo, traveling shorter distances (less than 500 miles) truck mode is used, and once the distance is larger than 500 miles the truck-rail intermodal is used. In general, rail or waterway are selected when the cargo is either heavy or needs to be transported longer distances. Truck is mainly used for lightweight cargo, or for shorter distances.
The tonnage and number of freight shipments within the United States are increasing steadily as demand for consumer goods and other products grows, and as manufacturers and retailers move from inventory-based to just-in-time supply chain and distribution systems (Grenzeback et al. 2013). Table 2 summarizes the trends in freight transportation demand, which government and industry have typically measured in tons, ton-miles, and value (dollars) of goods moved. As Table 2 shows, the value of each of these measures has increased over each five-year period, dating back to 1997.
Figure 1 disaggregates ton, ton-mile, and value data by mode. In 2010, trucks moved about 72% of all freight tonnage, accounting for 42% of all ton-miles and 70% of freight commodity value. Rail accounted for only 11% of the tons moved, but 28% of ton-miles and 3.5% of total value. This reflects rail’s cost-effectiveness in hauling heavier, generally lower-value, commodities such as coal and grain, over long distances. Excluding international maritime shipments, waterborne transportation accounted for a smaller percentage of tons and ton-miles. Airfreight transportation constituted an even smaller share, except in terms of value (Brogan et al. 2013).
The purpose of this chapter is to provide an overview of current mode shares, and the factors that determine those shares. The first section examines mode shares and shifts from a historical prospective. The second section delves into the current distribution of freight traffic by mode, examining the roles each mode plays in the freight system, and how those have evolved in recent years. The third and final section examines the macro factors that have recently, or are currently, affecting mode shares from regulation to containerization, to the just-in-time phenomenon.
 A ton of goods moved one mile is counted as one ton-mile. There is double counting in the reporting of aggregate national freight transportation statistics because sources compile these data by mode, not specific shipment. Data sources count a ton of goods transported two miles by truck as one ton of freight and two ton-miles of freight movement. However, a ton of goods transported the one mile by truck, transferred to rail, and transported one more mile by rail is counted as two tons of freight (one by truck, one by rail), and two ton-miles of freight movement.