1 - unsignaled bidirectional track, Root Street to 61st Street only
2 - signaled bidirectional track
3 - northward main track, signaled for current of traffic
4 - southward main track, signaled for current of traffic
5 - signaled bidirectional track
6 - unsignaled bidirectional track, Root Street to 61st Street only
And tracks 3-4-5 continued south from Englewood to Gresham, signaled in the same fashion.
Eventually tracks 1 and 6 were eliminated. After the Penn Central merger in 1968, former New York Central trains were moved to Union Station via former Pennsylvania Railroad trackage. And by the early 1970's, track 2 was no longer being used. During the late 1970's, tracks 2 and 3 were removed entirely, leaving just tracks 4 and 5 between Chicago and Gresham. This move seemed unusual, considering that the railroad basically became a "left hand" railroad. Track 4 the most easterly surviving track, was signaled outbound only. Tracks 2 and 3 were officially owned by New York Central, later Penn Central, and were thus retired. Finally, full CTC was installed over this segment, eliminating the concept of current of traffic. And during the 2000's, bridge replacement actually resulted in a "new" railroad being constructed were tracks 2 and 3 had been.