One thing that I don't understand about that chart is how they have only 24 passengers/vehicle? From my understanding, that's not per car, but the entire train. Also the energy/passenger shouldn't scale linear. A train should be able to pull twice the number of people with little increase in energy output.

Correcting myself :) Everytime you rip to mp3 (or any lossy) format you will lose more data because the compression is lossy. If you start with a wav file, compress it to mp3 you have lost data, so when you uncompress it the wav file will be different. If you then recompress, it's going to apply the same lossy compression to this new wav file, not to the old original wav file. So with each compression you will lose data.