I've bought about a dozen Altamont timetables for use in planning over the years. They are handy teaching tools, for young planners, who have very little understanding of railroads.

The emissions calculations for locomotives and heavy duty diesel truck is in grams (of pollutant) per brake horsepower hour. This is the measure of emissions related to pure horsepower produced by the engine, without drive train and transmission losses.

I think I know that professor, too..... (or someone like him...?). I think what they were trying to do, (back at the dawn of locomotive emissions calculations) was to figure out how to measure the fuel consumption related to the engine rpm with each notch (1 through 8), and how much time was spent in each notch, in order to attempt to calculate total rail emissions.

Southwest Research "bench tests" of large diesels, and actual data from the rr's were finally used to come up with a pretty good operational cycle estimate, which is the basis of most of the estimates used today.