It is a webcam mounted on top of a walkway across the NS tracks in downtown Roanoke. There are several other threads on the ‘other’ Trains dot com forum about it, See:
http://cs.trains.com/trn/f/111/t/214273.aspx
http://cs.trains.com/trn/f/111/t/214173.aspx
http://cs.trains.com/trn/f/111/t/154777.aspx
That last one is the original thread and is quite long (89 pages!) and involved to go back and read it all now, but it has a lot of history of the cam and what people have seen and what some of the non-trains things are in the view. Just be mindfull that the early posts talk about some of the startup problems that have mostly been fixed and it works pretty well now.
Very good camera aimed at 4 busy tracks of the Norfolk Southern. Run Google Earth (or your favourite maping software) and enter these coordinates:
37°16’25.23"N, 79°56’22.37"W
That is the location of the camera. It faces West-SouthWest toward the Virginia Museum of Transportation.
Here is a link to one of the methods of viewing the cam: