I'll just chime in with a few good things I know about the D&DR.
Right after they started operation, they undercut the main st bridge in Pburg, to permit higher cars. They installed a 2nd switch on the mostly previously unused siding along the WASS in pburg, so it could be used as a run-around as well as an interchange track. Ive heard that they added a 2nd siding track there too, but have not been back to see.
Also (and this is big if u live in the area), they removed the 40mph grade crossing circuits, which probably hadnt been changed since the 1960's or so...and put in induction activated circuits appropriate for 15 mph running. The highway flashers used to come on minutes before the train reached the crossing, which was a real problem...