wire gauge

Maximum current for #20 copper is 11 amps.  If you are going to use wire it to control a loco like it was designed, that would be enough, but to just light the lamp, much smaller will work.  I'd get what you can find locally. in the 22 to 18 range, stranded.

Thanks Callnnc,i do want it to stop a train for a short time as i`m running 2 trains on the same track                                                                                                                                                                                                                                                                                                                                               Thanks again, Phil

Virtually every Lionel and MTH locomotive uses #22 wire for power and motors, so I can't see needing anything heavier than that.

Thanks GunrunnerJohn, i appriciate the help,                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  Phil

I had some of this wire (see pic)  leftover from another project. I have started using it for all those little postwar roller pickup wires that get crusty and stiff - Also for rewiring the motors when needed. it's a little larger gauge, but I primarily like that it is wicked flexible - much more flexy than the OEM wires