Hi Michelle, a diesel engine is the most efficent of the internal combustion engines. You get a better ratio of fuel economy with a train because you use the full capacity of the trains horse power to load capabilities no wasted fuel, and the train for a large part during it's travel doesn't have stop starts that are very fuel costly.
Also a train rides on steel rails with almost on resistance, plus the grades are at a low degree of climb and descent and fairly constant. Also the engineer isn't fussing with a CD, cell phone or putting on makeup while eating a Subway sandwich.
Michelle, that number is a bit misleading. Trains measure fuel economy by how much weight they move. The reported number is most likely 202 miles per gallon per ton. The locomotive alone probably weoghs over 100 tons. However, the fuel cost of moving freight is lower than by other forms of transportation.
Very valid points.
Maybe it's because the diesel engine don't power the wheels directly, it powers a generator that powers electric motors to drive the wheels. Just guessing?