“ Discontinuance of service on one line might have a substantial effect on the other. But this relationship is not unique in railroading. Congress is not unaware of the mutual interdependence of railroads. It designed a federal regulatory system that displaced a state regulatory system when the state system could defeat a carrier's attempt to discontinue a train. ”

“ The Chicago & Eastern Illinois Railroad (C&EI) filed a notice under § 13a (1) of the Interstate Commerce Act, 72 Stat. 571, 49 U.S.C. § 13a (1) , proposing to discontinue a pair of trains known as the 'Georgian,' operated by it between Chicago, Illinois, and Evansville, Indiana, and operated in conjunction with trains of the Louisville & Nashville Railroad (L&N) between Evansville, Indiana, and Atlanta, Georgia, crossing Kentucky and Tennessee en route. ”