ISRR meaning in Regional ?

The Indiana Southern Railroad (reporting mark ISRR) is a short line or Class III railroad operating in the United States state of Indiana. It began operations in 1992 as a RailTex property, and was acquired by RailAmerica in 2000. RailAmerica was itself acquired by Genesee & Wyoming in December 2012.

Indiana Southern Railroad operates 186 miles (299 km) of track from Indianapolis to Evansville. From Mars Hill (a neighborhood on the southwest side of Indianapolis) southwest through Martinsville and Spencer to Bee Hunter in Greene County, the ISRR runs on tracks that once made up the majority of the former Indianapolis & Vincennes Branch of the Pennsylvania Railroad. State Route 67 parallels the ISRR along much of this section. From Bee Hunter to Elnora the ISRR has trackage rights over the Indiana Rail Road. ISRR tracks resume from Elnora through Washington in Daviess County, Petersburg in Pike County, Oakland City in Gibson County, Elberfeld in Warrick County and Daylight in Vanderburgh County before terminating in Evansville along the former New York Central's Evansville & Indianapolis Branch.