92 Ill. Adm. Code 1500.120
Tracks Adjacent to Main Tracks
Section 1500
Section 1500.120 Tracks
Adjacent to Main Tracks
a) Except as to ladder tracks, the distance from the centerline
of any main track to the centerline of any adjacent subsidiary track shall be
not less than 15 feet.
b) The distance from the centerline of any main track to the centerline
of any adjacent ladder track in which switches are operated mechanically shall
be not less than 15 feet; in ladder tracks where switches are not operated
mechanically, 17 feet.