If you're
really interested in this, and are proficient with your computer, Railroad Model Craftsman had a two-part feature on virtual model railroading in the August and September 2005 issues. My computer skills

are well-known, but I read the articles anyway, and found the concept to be quite interesting. The author used software called Trainz Railroad Simulator, created by Auran Games, designed to run on a PC using Windows. There's more in the two articles than I can explain here, but the author recreated the Gilpin Tramway in Colorado. And I do mean recreated: the entire railroad, with all of the trackage, the same number of turnouts, all of the mines, towns, terrain, etc. The terrain was duplicated using Digital Elevation Models, obtained from the U.S. government either for free or at a very low cost. As an example of how accurate and complete this reproduction is, the author had a photo of an accident that was labelled as having been taken at a certain location. However, there were details in the photo that didn't agree with the stated location, nor did the terrain. By "flying" along the route of the virtual railroad, he was able to find the true location of the wreck and identify mill buildings in the background of the photo.
You can recreate any railroad, if you have the time, complete with all of the towns, cities, structures, etc. Or you can pick a location and freelance a virtual railroad. The line that the author chose was only 26 miles long, and it looks like this is a fairly complex project, so you might want to investigate further before deciding to recreate the latest version of UP or BNSF. You should have no trouble obtaining the appropriate back issues.
If you've no room for a layout, and very little money for "hardware", you could instead buy "software", and build the layout in your computer. It appears to be as complex and as time consuming as building a three-dimensional layout though, and, if you build well, just as rewarding.
Wayne