I am a train fan. I take Caltrain fairly regularly, and I have taken Amtrak a couple times out to Davis.
After a recent episode of Forum, I have begun to think more about what it means to fly. So I did a little research, and found that train travel is by far the best way to travel in terms of energy consumption. Cars, buses, and airplanes use about the same amount of energy per passenger mile, while trains use about 60% of what the other modes use.
Of course, Amtrak is also remarkably more expensive, about double what you would pay for a plane or bus. That will hopefully change.
As our climate problem gets worse, and more people get concerned about it, I would hope to see hundreds of billions of dollars doing into train travel. Where do we get this money? The military budget. Hopefully Americans will learn to swallow that one.