Generally accepted definition of a Regional or Shortline Railroad

There is no official or legal definition of a "short line" railroad, but the American Short Line And Regional Railroad Association and the railroad industry apply the term to any railroad with less than 100 miles of main line track.

The Surface Transportation Board classifies a Class 1 railroad as one with an annual operating revenue greater than $255.9 million dollars; a Class 2 railroad as one with an annual operating revenue between $20.5 million and $255.9 million dollars; and a Class 3 railroad as one with an annual operating revenue of less than $20.5 million dollars.

The Association of American Railroads classifies railroads as Class 1, Regional, and Local. The A.A.R. and I.C.C. classifications of Class 1 railroads are the same, but the A.A.R. classifies a Regional railroad as a line-haul railroad with an annual revenue between $40 million and $255.9 million dollars and more than 350 miles of track. Local railroads include line-haul railroads falling below that criteria and switching and terminal companies.