In the United States, a regional railroad is a railroad company that is not Class I, but still has a substantial amount of traffic or trackage (and is thus not a short line). The Association of American Railroads (AAR) has defined the lower bound as 350 miles (560 km) of track or $40 million in annual operating revenue. (The Class I threshold is $250 million, adjusted for inflation since 1991.)
List of regional railroads
The following railroads were classified as regional by the AAR in 2007.