The trains will start at the interchange track on the lower left corner. From there, the operator on the outer loop will pick up the cars, run around the track as many times as needed and then spot the cars at the other interchange track by the side of the mountain on the upper right. At that point, the operator on the inside loop will cross over to the outer loop to pick up those cars and then move back in to the inside loop to deliver them to the various industries.
There has been one change in the design, the upper interchange by the mountain has been reduced to a single spur due to radius limitations.
Because this is such a small layout, the curves are quite sharp. The inner loop is about 10" radius and the outer loop is 11 1/4". Therefore, primarily four axle diesels will be used along with 40'-50' freight cars, which is just as well considering the size of the spurs.
The industries are a grain elevator, a candy factory and another factory which is still trying to figure out what they'll manufacture.
Construction is relatively lightweight. The benchwork is built using 1/4" wood. There is a 1.5" extruded foam base that is carved to form the terrain. Lightweight spackle is used to smooth the land forms.
The base is actually a box that will have a storage drawer, a slideout for electronics and a middle compartment for containing the wiring. The top lifts open on hinges like a toy chest. The end result that is envisioned is something like this:
Currently, all the track is down and the layout is fully functional with DCC (Digitrax Zephyr Xtra). Scenery started, but is progressing slow as we're all too distracted running trains! Here's a picture of the current status (January 2011).
You can follow the progress of this layout on the build thread I have at nscale.net forums.