Compare 423 ton-miles/gallon for a locomotive vs. a typical 18-wheeler.
That's about a 3.25-to-1 advantage for rail. In other words, rail can move the same tonnage the same distance using roughly 69% less diesel.
Freight rail is extraordinarily fuel-efficient compared with trucking.
While the dollar figures are out of date, the basic thrust of this speech from 2005 are on target.