User blog comment:Stormwell/Thoughts on Technology/@comment-1500935-20140210135550/@comment-1500935-20140213165838

Current doesn't work with negatives and positives unless you're talking of alternative current, and in this case it would only provide power to the trains' motors. Yet, if you compare it to how a simple light bulb works, one set of tracks could conduct the electricity from the generators to the trains, while the other set would have it go back to it, closing the electric circuit. When I think of it, that's why we only need one set of rails for modern trains, because the current runs on lines suspended above the tracks, thus reducing the shock hazards, something Sokolov clearly did not think of.