The benefit of a bus and one or more 'subs' is that each can be treated as an entity electrically, and dealt with while retaining operations around the rest of the layout. Say you're one of what I think is probably a relatively few people who like to hear 'neutral' engine sounds, an idling prime mover, a steamer with its 'soothing' turbo-generator whining, the spits of the relief valve on a diesel....whatever makes you feel warm 'n fuzzy, you can keep power going to one part of the layout while another has a hard short and is shut off by its protection circuitry, or that you shut down via a toggle wired in series into that sub...you can work on it and continue to hear the idling, or even a steamer running around a closed and safe loop while you work.
It takes more thought and materials and work up front, but there are rewards to be had if you like convenience and other benefits when you get your whole layout up and running.
I learned about the tail-light bulb 'limiter' wired in series, I think from Joe Fugate when he was active on the Model Railroader forums about 19 years ago. You need a 2.5 amp analog tail light, and you wire it into the line between the bus and any sub you create per the reasoning above. When a short happens, it takes up the amperage rush, at least to its maximum rating, and will spare other components down the line from the inrush of damaging amperage. The method has its detractors and some limitations, but for those operating a Zephyr or NCE system with only 3 amps or so, it will do a good job. Just remember that, when it glows bright, it signifies a problem, and it will get HOT!!
