I was with USRA during the early post-conveyance years, and it was interesting watching the changes in traffic flows. As far as your questoin goes, the Ft. Wayne line was quite heavily used into the 1980s. In fact, there was considerable internal resistance at Conrail to the idea of downgrading the Ft. Wayne line in favor of running everything via Cleveland and over the former NYC. The problems NS has had with congestion between Elkhart and Chicago suggest that maybe those at Conrail who objected to the downgrading had a point.
Through freight traffic wasn't moved off the Ft. Wayne line until 1989, and Amtrak service followed fairly shortly thereafter.
Other downgradings I watched happen were the "Main Line Davis and Lenox" (former PRR Indianapolis to Terre Haute, former NYC from there to Lenox, IL), the PRR portion of which became the "Greencastle Secondary" and then the "Limedale Industrial Track" and was then abandoned, and the main line from Terre Haute to Lenox, which was simply abandoned (MOPAC bought the segment on which they had trackage rights, from Pana, IL to Lenox). The "Scranton Division Main Line" (former DL&W) was sold to D&H. The "Panhandle" main line out of Chicago to Logansport and Kokomo was abandoned, and of course eventually the eastern end of the Panhandle from Pittsburgh to Mingo Junction was abandoned as well. The former Erie main east of Pymatuning, originally classed by Conrail as a main line, has been sold or leased to short lines. And the list goes on. There's a lot less railroad out there than there was even in the 1980s.
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