Well actually with flat routes you can actually get away with fewer tiles either side of the line if (and with respect to the guy who posted earlier about viewing from a hill 500 feet above and 2km away from the track) you are focused on what is visible from the cab and/or train. The flexibility of Trainz and Surveyor is that you can use it how you want, but my approach is and has always been, it is a means of creating a nice railway which you can drive or ride along, not a vast tract of landscape.