27 TRANSPOR T A TION Coal and minerals usually get from mine to market in one of three ways by rail truck or water transpor tation Coal can also be shipped by way of conveyor to mine mouth power plants located nearby In all cases a modern reliable and economic transportation infrastructure is an important factor in the overall cost and competitiveness of domestically mined products Min ed products represent nearly three out of every fve tons of revenue freight carried by railroads and approximately onehalf of all commodity tonnage handled by barge lines operating on the nations inland waterways Coal shipments alone account for 14 percent of total freight revenue and 31 percent of total freight tonnage transported by Class I railroads When it c omes t o barges 17 per c ent of coal is mo v ed via our inland w at erw a y s While some mining commodities are shipped intramodally using a single form of transport between mine and destination others are moved intermodally by diferent types of carriers For example a coal shipment might be hauled a shorter distance via truck to a loading terminal then placed aboard barges or rail hopper cars for the longer trip to a power plant For many mining products trucks and in the case of coal also conveyor systems commonly provide relatively shorthaul transportation to railroad tipples and barge terminals However rail carriers also originate many shipments and link with barge lines Great Lakes carriers and drybulk oceangoing vessels to complete shipments to domestic and export customers Railroads Mining products carried by rail typically include coal crushed stone sand and gravel metallic ores metals and nonmetallic minerals In 20 18 these mining commodi ties accounted f or about a thir d of total rail commodity carloadings in the United States according to Association of American Railroad AAR data As a single commodity coal has been a signifcant annual user of rail transportation According to AAR mor e than 500 million tons of coal were shipped domestically by rail in 20 18 Unit trains large groupings of rail cars assigned to a specifc nonstop route between a mine and power plant account for more than half of railroad coal ship ments Because the entire train is dedicated exclusively to moving coal in railcars carrying 100 to 125 tons each economical high volume shipments are possible Among other major mining commodities hauled by rail 20 18 totals included 183 million tons of non metallic minerals 47 million tons of metals and products 43 million tons of stone clay and glass prod ucts and 66 million tons of metallic ores Because mining products represent such an important segment of railroad business there has been much focus over the past t hr ee decades on improving rail efciency and capacity In addition to increasing car capacity many railroads are now using more fuelefcient a lternating c urrent locomotives instead of older d irect c urrent models As with mining railroads have embraced information technologies such as electronic data interchange EDI to improve efciency EDI permits shippers to communicate com modityspecifc information to customers track shipments while in transit and dispatch timesensitive information such as bills of lading invoices and payment for rail car services