Thank you for the positive reference, Alan. I would just like to add that if anyone has references to the real numbers for a particular Amtrak service I would be happy to add it to the table. Right now the data I have for diesel-electric locomotive-hauled trains is not the greatest. I have information from one trial service for the Colorado railcar+trailer (392 passenger-mpg if all seats taken), and one data point taken from the fact that commuter rail trains (which I've seen with my own two eyeballs :-) ) can be 10 bi-level cars long with only one 3000 hp locomotive, which apparently burns 761 L/100 km. Knowing the seating capacity of each car yields the number I calculated - 421 passenger-mpg with all seats filled. Amtrak single-level trains are likely to have less than half the seating capacity but not significantly different mass (less dense seating, a restaurant and baggage car perhaps) and if they're on average half full then you would expect something on the order of 1/4 the efficiency overall.

This is too much handwaving for my liking - I'd like to nail a more exact number down. The difficulty of finding such information continues to astound me - surely the energy efficiency of transportation service should be an important factor in public policy.

Maybe I'll try some more searching. I've started looking through the academic literature and there is a stunning paucity of data there as well. Maybe I'm just not searching in the right place - anyone have any ideas?