That's a tough one...

My first thought was to suggest using first surface mirrors to create the illusion that the track continues into the backdrop, but after thinking about it I'm not sure that is the solution in this case.

This almost sounds like a job for Photoshop.  If you took a photo of the area where the abandoned right of way is and then shot photos of existing track with similar surroundings/background etc., I wonder if the images could be combined and blended to make it appear that the track work still exists in that location?

I think with the right photos and an editor who is a whiz with Photoshop, it might be possible.

Digital Magic

I agree with blue. Good hi-res image of the right-of-way as it exists today is the place to start. Shoot it from the correct angle to match your layout/background viewing angle. Then to make it really slick, take another hi-res image of a section of actual model track that matches the route in the image. Try to shoot it from roughly the same angle of view as the first picture. Trim the track image out of its background and overlay onto the right-of-way image. A little messing with perspective/blurring/saturation and some brushed on weeds, is all that likely will be needed to make it look real. Track in the image will match the layout track as it fades into the distance. Sounds pretty straight forward. Considering Photoshop's capabilities this project would be elementary.

Post pics when your done!

Exactly!

Yes, I'm really only scratching the surface of Photoshops capabilities but I'm sure I could come up with something if I needed to do this.  Other image apps would likely work as well.

I've used Photoshop to cut subjects from photos to insert them into other photos before and LK & O has described the process very well.  The key to cutting in Photoshop IMO is the magnetic selection tool!  Learn to use it well and anything is possible.  Don't believe what you see in digital images! [smile]

Time Well Spent

Again Blue, good suggestion. The magnetic lasso tool sure is a timesaver... unless you have a little rivet counter in you. The standard lasso tool takes 100 fold longer to use than the magnetic lasso but the end result is pure perfection. Zoom in on the image until you can recognize individual pixels. Painstakingly trace the rail and tie. At this level of magnification you will see there is no such thing as a sharp line in a photo. Everything will have a fuzz. Trace down the middle of the fuzz of the edges. Periodically zoom out so you don't lose track of where you are on the image. When finished you will have an exact object to work with that contains no stray artifacts that may become troublesome later on when you begin applying various filtes and effects.

Something else to consider is resizing. It is always bad news to enlarge an image. That is why it is so important to start with a hi-res image. It starts out big so there is no need to enlarge it. If you can get your hands on a 10 megapixel camera or higher do so.

Here is the math:

Consumer inkjet printers print at 300 dpi (dots per inch).
For every inch wide of your backdrop you need 300 pixels of camera sensor.
2 megapixel sensors = approx. 1600 pixel wide x 1200 pixel tall images
Therefore a 2 megapixel camera image prints best at no larger than 5.3" x 4" (1600/300 x 1200/300)
See why a high megapixel camera is desired?

The RIP (raster image processor) software inside your ink jet printer will enable the print head to print at 1200 or 2400 dpi however this is just eye trickery. There is only 300 DPI worth of data to work with from the camera sensor. The RIP is using data from adjacent pixels to determine what to put between them hence why it is not real image data. The manufacturers know people will enlarge images so they build in the RIP so the picture doesn't come out total crap from being enlarged.

Printing resolution

While I agree with LKandO's post in general the printed resolution required for a given image depends a lot on the distances the the image is going to be viewed at and the ultimate print quality actually required.  300dpi is the standard for prints that will be "held in the hand"; portfolios, magazines, smaller art prints, etc. As the print gets larger there comes a point where the viewer has to stand back from the image to view it properly. At this point the dpi can be safely reduced since the eye can know longer resolve the dot structure at 300dpi. The exact dpi required for the larger print can depend on a lot of things but a background image viewed from a few feet away could be pushed down to 150dpi pretty safely I would think.
Also most decent image processing softwares have pretty impressive abilities  to resample images to a higher apparent resolution.