If you'll allow a small amount of self promotion (I was a co-author), let me recommend Morning Sun Books "D&H Color Guide to Freight and Passenger Equipment" as a source of info on, well, freight and passenger equipment.
The other relevant Morning Sun volumes (D&H in Color, Volumes 1-3) offer additional info and lots of pictures, and their "Trackside in the Albany Gateway with Gerritt Bruins" has some detailed coverage of the Binghamton trains and the commuter trains.
The classic railfan book on the D&H, Jim Shaughnessy's "Delaware and Hudson" was published in 1967 by Howell North, and was recently reissued. Definitely worth a look.
By the time of the Dumaine-era upgrade of passenger service (1967, linked to the Montreal Word's Fair of that year), the Montreal-Albany route was all there was left.
Farther back, as of 1960 or so, there were the two pairs of trains to Montreal (the Laurentian and the Montreal Limited) a single pair of day trains from Albany to Binghamton (generally 1-2 coaches and an RPO) and either 1 or 2 pairs of commuter trains north out of Albany. I can't recall right now when the commuter trains came off, the Binghamton service went away in early 1962 if memory serves.
Prior to Dumaine, all of this was behind RS2/RS3 power. Simple reason for that: that's all the road power the D&H owned from intial dieselization in 1946 til the first RS11s in the early 60s. It was one of the least diverse motive power rosters in all of American railroading. Even after the newer power arrived, they lacked steam generators, so RSs were the rule on passenger trains until the PAs arrived.
One oddball feature was that for the last few years before Amtrak, the Montreal trains would occasionally draw Erie Lackawanna E units for power. During the winter especially, the PAs would be doubled up for extra steam heat capacity, leaving the RR power short (four trains daily, two pairs of PAs, do the math...). EL and D&H were both in the N&W Dereco camp at the time, so the semi-surplus Es were a natural choice. Many of their sisters were hauling freight trains in Ohio at the time.
After Amtrak started up the Adirondack in 1974, the PAs were sent out to Morrison Knudsen for rebuild, and for a while, RS36s and RS3s could be found on the train.
Amtrak substituted Rohr turbos for the PAs in the summer of 1977, and these were replaced by ordinary amtube consists in the early 90s. Genesis and amtube consists have ruled the roost now for nearly 10 years.
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