On YouTube I did a serach for NYC railroad films.
One of those films (1950's New York Central Railroad - The Big Train)
described the ongoing research done by the New York Central back in the
50's:
formatting link
8:16 into the film they mention a new type railroad lamp (they show aswitch lamp) that could be self-powered by atomic energy and would run for 7
years...
What 'atomic' referred to wasn't explained, but I'm wondering if anyone is
familiar with the process???