How Sustainable is Train Travel?

It is Thursday afternoon and I am on an Amtrak train on my way back from speaking at the Ethical Sourcing Forum in Manhattan. I just took a look at the Arrive magazine in the seat pocket in front of me and it was the March /April "Special Green Issue". It is pretty good for a seat pocket magazine and includes a well written feature on the challenges and opportunities of wind energy.

One thing took me by surprise. In the editorial, Joe Boardman, President and CEO of the publication, explains that rail travel is about 17% more energy efficient than air travel and 21% more efficient than automobiles on a per passenger mile basis. I had been sitting here on the train thinking how green I was being going from DC to NY by train rather than flying or driving. 17% and 21% is better than nothing, but it doesn't seem that much better in the grand scheme of things. I had thought the train would be 80% or 90% better - after all, it doesn’t have to get off the ground and I always understood that to be the most energy intensive part of air travel.

According to Freight on Rail a UK based partnership of the rail freight operators, per tonne carried, road transport will requires between 4 to 7 times more energy than rail. – The case for rail, Railfuture 2004. That is more like I would have expected.

Does anyone know where the 17% comes from or how to reconcile these two data points?