I have also followed Johns general advice. After riding the train you will see how the entire Rockwood area is laid out.
One important item is safety. Walking through the Rockwood "cut" there is a part that has no side clearance. If possible carry a scanner, check the schedules, and keep an ear to the air and ground for appraoching trains and motor cars. The motor cars seem to run faster than the trians and sneak up on you. Same with a few more but shorter cuts north of the big cut at Rockwood.
We don't want to upset D&S by injuring a photographer. As John states, use common sense and keep a low profile.
Also, watch where you park at Rockwood..there are lots of no parking signs growing in the weeds as well.