Resumen
Since 1970 and especially since railroad deregulation in 1980, there has been a proliferation of hundreds of new short line rail companies. These railroads range in length from about a mile to more than a thousand miles (those over 350 miles are called ?regionals?). They were mainly formed when major Class 1 rail systems spun off marginal trackage. This paperdiscusses the reasons for the short line renaissance.