Hi David
Here is a look at the west end of the Spokane locomotive service facilities and yard complex when under construction at the Northwest Trunk Lines. The photo shows about a 20x7 area of benchwork.
In this photo the mainline is being laid around the perimeter. The track inside of the main serves as the switching lead for the coach yard and the freight arrival and departure yard. The freight A/D yard ladder is on the left side of the layout and the coach yard ladder is visible in the right foreground. The short tracks and switch ladder above the coach yard are diesel ready tracks. A Ross turntable is at the head of the peninsula and another 20+ feet of yard extends behind the photographer.
The track in the photo is MTH Scaletrax with #4 switches used for the yard ladders. In the upper left a curved switch is being hand laid with ScaleTrax rail and a Ross frog to the Ross #8 curved switch pattern. Curved switches can be extremely valuable for lengthening a yard lead or a siding around a curve.
Here is a control panel view of the yard area shown in the photo. Red indicates occupied tracks and green indicates clear blocks. The yellow highlights an active route.
Be advised that a turntable and roundhouse large enough to accommodate large steam locomotives will fill up a 4x8 area all on its own.
1700 square feet is a large space but O scale can make it look small. If you have the ability to expand your layout over time to use that much space it will be worth it to you to plan carefully to make the most of the space, build a user friendly layout and avoid as much tear down and rebuilding as possible.
One of the best resources for learning about the art of layout design is John Armstrong's Track Planning for Realistic Operation. I highly recommend picking up a copy.
http://books.google.com/books?...&ved=0CDEQ6AEwAQ