The New York Times seems to be giving Amtrak some respect in an article on the national passenger rail system's rising ridership. (Free registration required.)
The facts on fuel economy are simple:
Amtrak can move a passenger a mile with 17.4 percent less fuel than a passenger car can, and about 32.9 percent less than an airline can, according to the Oak Ridge National Laboratory.
As a resident of rural Colorado, I do depend on Amtrak for some cross-country travel. (I just rode it back from Virginia.) The cross-country trains are heavily used, but some politicians don't like them. Don't ask me why--we subsidize cross-country air travel heavily, not to mention interstate highways.
...dropping states from [Amtrak's] itinerary would hurt its political support, especially in the Senate, where thinly populated states are overrepresented relative to their population.
And if you live in southeastern Colorado, for instance, Amtrak is actually fairly convenient -- as long as you want to go in the direction of Los Angeles, Kansas City, or Chicago!
In Colorado, the Salazar brothers at least have good pro-Amtrak voting records.