Freight railroads in the U.S. are designated according to their annual operating revenues as Class I, II, or III. Approximately two-thirds of the nation's rail network (~92,000 route miles) is owned by six Class I freight railroad companies. Class II and III make up 600 short line railroads and include private, public, and quasi-public operators and owners. Railroad property rights often come from easements, license agreements, and/or adverse possession. Transmission planners can use rail data to identify corridors where transmission lines may be co-located with rail infrastructure to streamline permitting, minimize land use conflicts, and reduce costs.