There is no I-86 *north* of Corning!
only east or west..
and you didnt say which direction you were going, so we dont know which side of the highway you are talking about..
The Lackawanna is still in use West of Corning..so the DL&W there still has rails in place..
so thats probably not where you were.
Traveling Eastbound on Route 17/I 86, between Elmira and Lowman, the DL&W roadbed has been very visable for the past 40 years as a dirt access road right alongside the highway..(to the right (south) side of the highway as you travel East out of Elmira)..there is major construction going on in that stretch right now, and the DL&W roadbed is being used as a road for construction vehicles..(and it looks like its in danger of being wiped out in spots..)
Could that be where you mean?