Chad,
Here's a link to what appears to be a pretty complicated wiring setup. However, if you look at the individual sections, you'll see it's not as complicated as it looks. For example, take TIU #1 in the center. You'll see that it's being fed by a couple of Z4000s. From the TIU there are separate runs to 4 terminal blocks, 1A-1D. These then distribute power to multiple track blocks. What the diagram doesn't show is that each line from the terminal block is actually 2 wires, 1 to the outer rail and the other to the center rail.
I'm no wiring expert and don't fully understand all the DCS terminology, so my view is certainly simplistic. But from what I see int he example is that the power blocks being fed from the terminal block are fairly close together. To save on wire, one could use bus wiring to run single wires for positive and negative with feeders to the outside and center rails for each block . However, DCS prefers shorter runs for at least the center rail. Therefore, one could run a bus for the outer rails and individual (star) runs for the center rails. Some will say DCS needs individual runs (of the same length?) for both outer and center rails, but there are plenty of examples where bus wiring was used successfully for the outer rails. I think that is what Carl was referring to with Marty's layout.
There is also some conflicting advice given regarding the gauge of wire needed. Of course, most of that is because not all layouts are the same size with the same length of runs. Obviously, train sets are sold with nothing larger that 16AWG wire leads directly off the power source. We know this works okay for small layouts, but can become problematic the larger the layout gets, so larger wires need to be used for different purposes.
