The line parallels highway 550 From Durango to Hermosa with several easily accessible points by car along that portion of the line.
The highway 550 grad crossing north of Hermosa is a popular spot but there are many others.
North of there there are great spots with just a bit of work, including the US 550 overpass before the railroad and the highway separate.
Rockwood is another good location for fairly easy access.
Beyond Rockwood there are many spectacular spots in the Animas River Canyon, but it takes either riding the train or a fairly tough hike to get to them.
If you chose these places, plan on only one location for the day, or one in the morning and one in the afternoon.
Catching the trains in Silverton is nice as well, and there is some access south of Silverton on County Rd 31.
The Animas River Bridge is a short hike beyond the end of county rd 31 and is a nice location.