Ownership of the U.S. rail industry is divided between eight Class I railroads (those with more than $258.5 million in annual revenue) and about 550 regional and short-line railroads. The eight large railroads own about 70% of the 273,700 track-km (170,000 track-mi) and account for about 90% of industry revenues. The remaining 30% of track-km belongs to the regional and short-line railroads, which must operate and maintain them with 10% of industry revenues. U.S. railroads function as an integrated network; freight originating on a short-line railroad can be delivered anywhere in the United States, Canada, or Mexico. Equipment is freely interchanged, so the small railroads must handle the same heavy cars as the Class I railroads even th...