Typically, we measure energy efficiency in transportation—especially automobiles—in a simple metric of miles per gallon (MPG). It is a little more complicated in the freight world of planes and trains, however. If you look only at MPG for locomotives, you would think we haven’t made much progress in energy efficiency. Since 1960, the MPG for rail cars has only improved 23 percent (from about 8 to 10 gallons per mile), while automobile gas mileage has more than doubled.
But this is highly misleading, because the weight of the average rail freight car has increased by 44 percent, and the amount of total freight miles (which is not the same thing as rail-car miles traveled) has tripled. In fact, the energy intensity of locomotives has improved substantially, with BTUs per freight mile falling by 65 percent since 1960. In other words, although total freight-rail miles have tripled since 1960, total railroad fuel consumption has remained about flat. If railroad locomotives had made no efficiency improvements since 1960, we’d have needed 9.2 billion gallons of fuel in 2009 instead of the 3.1 billion gallons actually consumed.
This illustrates two points: first, improvements in energy efficiency often translate into greater consumption of the energy-consuming good—what energy economists call the “rebound effect.” Second, unlike other areas where government mandates drove efficiency improvements (i.e., refrigerators) there were no government mandates driving locomotive engine efficiency gains.