Detroit, Toledo and Ironton (DT&I) Railroad
Click Here for a well-written history of the DT&I.
This is a 26 February 1982 view of the Royersville tunnel. The last train ran through just a few weeks later in early April 1982, before a large rock fell from the ceiling and the RR decided to close it. The CH&D RR shared this tunnel from 1882 to 1917 and for them they called it tunnel #4.
Same tunnel in 2012: