I can definitely help with Durango, and somewhat with Chama.
Durango:
You can pace the trains (heading North) pretty much all the way to Rockwood via highway 550. Just north of Durango is a flat river valley and it stays this way until Hermosa. At Hermosa the train (which has been to your right) crosses highway 550 and the railroad is now on your left. At this point it's mostly hidden by homes, and pine trees. But keep going as there are some breaks which make for some pretty good places to take photos, especially the 550 bridge over the railroad. I would suggest taking a look at a few maps to get familiar with the area. After the bridge all you'll see of the train is smoke.
Rockwood offers some nice photo spots as well, however you have to get off 550 and take the road to Rockwood. Not sure of the road number off the top of my head (200? maybe), but it's a right turn off 550 and there's a big sign saying "Town of Rockwood", or "Village at Rockwood", or something similar. At Rockwood there's a wye, some MOW equipment, and a small depot. Some trains will stop at the Rockwood depot.
After Rockwood it's nearly impossible to see the train again until Silverton. Any photo ops north of Rockwood requires hiking out to the tracks. It's possible in some spots, but not recommended. You really need to know the area to do it. There aren't any well defined trails, or roads to get out there.
Follow 550 on this map to see how it follows the railroad:
Google Map Durango
Chama
I've only followed the trains here once, but highway 17 offers the best way to follow the trains. You can pretty much follow a train all the way from Chama to Cumbres. But after Cumbres the highway and railroad divert so you don't see much until Antonito. But there are some dramatic photo spots along the highway, including a grade crossing. And the train stops at Cumbres to take on water from the water column. Pretty neat stuff.
Follow 17 on this map and you can kind of see how it follows the tracks:
Google Chama Map
General Tips
It's pretty easy to track and pace the trains in a car. Use the smoke to spot the trains approximate location. The trains travel slowly so you can get ahead of them and and set up for photos. But here are some warnings to look out for when pacing on the highways:
1: You won't be the only person stopping their car to take photos. Many people do it, so look out for cars in front of you making a sudden turn to the side of the road.
2: 550 is a major highway. A lot of people speed on it (possibly even myself /DesktopModules/NTForums/themes/mls/emoticons/blush.gif ). The posted limit is a joke, so just be aware that very few obey the actual limit unless there's a state trooper nearby. Average speed to expect is around 65 mph. So be careful when pulling to the side of the road for photos. Not everyone will stop to see the train. Watch for big trucks speeding down (south) the mountain too. Also don't cross the road at any times. It's curvy in spots and you can't always see far enough to be sure it's safe to cross. And traffic can be surprisingly heavy at times too.
3: Sometimes it's pretty annoying to other drivers when a bunch of people pull onto the side of the road to take photos. There's not much of a shoulder on either 550 or 17, so just be cautious. There are some larger "scenic" pull outs, so try to use these if possible. 17 is a bit better since there's not as much traffic as 550.
John, when are you heading out to the area?
