Trains have batteries. They don't last forever, though, and in modern times, even a simple passenger car comes with a sophisticated software... which may be ill designed and shut down the system in the 'wrong' kind of emergency. (I could tell stories.)

And you may not want to run a train across a section of broken but still possibly live wire. It shouldn't be a problem (trains are pretty good Faraday cages), but with this sort of voltages you prefer safe over sorry.

- Jake

Friends come and go. Enemies accumulate.