electrical/fire safety

a master shut off is good for any project, including vintage cars.

Ditto on a master disconnect. 

Dale, I think you gave bad advice.  The ZW's internal circuit breakers aren't reliable enough to provide adequate protection.  If that #22 wire doesn't melt quickly enough, one could do damage.

I don't think you interpreted Dale's post correctly. He said to use external protection. The wire test was just that-a test.

After a few "letting the smoke out" incidents and a lot of arc and spark track welding at 15 amp levels, (2 PH 135's wired in parallel). I installed a track circuit fuse system that has maximum 7.5 amp fuse.  Accessories are fused separately at 3 amps. Most noted accessory failure was Atlas switch motors via a stuck momentary push button. Atlas switch motor failure was eventually solved by installing 6924 relay boards that time out after the initial momentary input. The 6924 relay boards are rated at 8 amps, but I found that the 7.5 amp track fuses would still allow board failure so I installed 3 amp fuses on the power routing circuits.  IMO, Modern, high amperage, model trains are not your Grandfathers trains, and may require a little more circuit protection than you think.
Mike CT
(8) track circuit fuses each 7.5 amps

Accessory fuses.

I have pictures of an Atlas switch motor that failed. None have failed since I installed the 6924 relay boards.

6924 relay boards. Note the track circuit fuse above each relay board.

As others have mentioned one switch turns it all off. The receptacle by the power control area is switched by the train room door.
Receptacle lower left is switched.  All 110 volt power, to the layout, is from this receptacle, via a plug strip.

Always been impressed with your wiring, Mike. Real professional looking job.

Mike, as a former telephone technician who was always encouraged to make a job so neat that it "looked like it grew there" I salute your wiring skills.

You're the poster boy for NEC 110.12. Mechanical Execution of Work.

"Electrical equipment shall be installed in a neat and workmanlike manner."