of freight railroads There are four different classes of freight railroads: Class I, regional, local line haul, and switching & terminal. Class I railroads are defined as those with revenue of at least $346.8 million in 2006. They comprise just one percent of the number of freight railroads, but account for 67 percent of the industry's mileage, 90 percent of its employees, and 93 percent of its freight revenue. A regional railroad is a line haul railroad with at least and/or revenue between $40 million and the Class I threshold. There were 33 regional railroads in 2006. Most have between 75 and 500 employees. Local line haul railroads operate less than and earn less than $40 million per year (most earn less than $5 million per year). In 2006, there were 323 local line haul railroads. They generally perform point-to-point service over short distances. Switching and terminal (S&T) carriers are railroads that primarily provide switching and/or terminal services, regardless of revenue. They perform pick up and delivery services within a certain area. Traffic and public benefits U.S. freight railroads operate in a highly competitive marketplace. According to a 2010 FRA report, within the U.S., railroads carried 39.5% of freight by ton-mile, followed by trucks (28.6%), oil pipelines (19.6%), barges (12%) and air (0.3%). However, railroads' revenue share has been slowly falling for decades, a reflection of the intensity of the competition they face and of the large rate reductions railroads have passed through to their customers over the years. In 2011, North American railroads operated 1,471,736 freight cars and 31,875 locomotives, with 215,985 employees. They originated 39.53 million carloads (averaging 63 tons each) and generated $81.7 billion in freight revenue of present 2014. The average haul was 917 miles. The largest (Class 1) U.S. railroads carried 10.17 million intermodal containers and 1.72 million piggyback trailers. Intermodal traffic was 6.2% of tonnage originated and 12.6% of revenue. The largest commodities were coal, chemicals, farm products, nonmetallic minerals and intermodal. Other major commodities carried include lumber, automobiles, and waste materials. Coal alone was 43.3% of tonnage and 24.7% of revenue. Coal accounted for roughly half of U.S. electricity generation and was a major export. As natural gas became cheaper than coal, coal supplies dropped 11% in 2015 but coal rail freight dropped by up to 40%, allowing an increase in car transport by rail, some in tri-level railcars. US coal consumption dwindled