Not sure why AlgorithmicTime's comment is dead, so I'll reply here. Long distances are probably tricky to electrify. I don't know enough about US railroads (wha

Not sure why AlgorithmicTime's comment is dead, so I'll reply here. Long distances are probably tricky to electrify. I don't know enough about US railroads (what little I know of US railroads comes from playing Ticket To Ride) to comment on the feasibility, but there are very long electrified railways in China and Japan, across difficult terrain. There is probably not much benefit in feeding electricity from regenerative braking back onto the overhead line if it's a very long segment with only one train (no one to use the power + transmission losses). I wonder at which point diesel becomes the cleaner option here, if ever. One the one hand, you have to lug a lot of fuel around over longer distances (or you need refueling infrastructure). On the other hand, transmission losses can be significant.