1. Begin by approaching that ledge ahead.
2. Drop to this walkway below.
3. Drop to the ground and head to that walkway ahead.
4. Take out this patrol, then climb the ladder at the end of the walkway, visible here on the right.
5. Head left and crouch-jump over this ledge.
6. Approach this heavily-defended area with caution. I found sniping them to be difficult -- their RPGs are too fast. Respond in kind with your own rockets. The defenders above can be safely avoided once you are under the overpass ahead.
7. Enter through this door on the left.
8. Descend the ladder then exit through a door and head right. Fight your way down the train tracks.
9. Climb that ladder for a large medkit. Be careful as it is defended by a guard. Come back down the ladder and continue ahead.
10. Go through this door and climb a long ladder.
11. If you hadn't taken out the guards above, you'll be on even ground with them now.
12. Climb up the left ladder.
13. Grab the large medkit on the other side of this opening, then drop through to an easy jumping puzzle.
14. You can take some damage as you drop to these pipes -- that's another large medkit at the bottom. Drop through another opening in the floor and prepare for a fight.
15. Continue to the right after grabbing two medium medkits and an armor vest straight ahead.
16. Drop below and continue through the door with the green panel visible ahead.
17. Activate the green panel seen here. The large door blocking the tracks opens. Drop to the train below.
18. Hop aboard and the train begins moving on its own.
19. When the train comes to a rest, climb the ladder seen ahead.
20. Enter the door with the green panel seen here on the right. Be careful as there is a guard just inside the door. The guard I am firing at here is protecting ammo, armor and a medkit.
21. Activate the green panel seen here then rush back to the train.
22. Ride the train to this reloading area.
23. Climb this ladder.
24. Activate the green panel to load these explosives. Return to the train and it continues down the tracks.
25. When the train comes to a stop, climb the ladder seen ahead, similar to the one you climbed earlier.
26. As before, fight your way to a green panel and activate it before rushing back to the train.
27. As the train continues down the track the next area will load.