unit train

American  

noun

1. a freight train of uniform consist that remains coupled, carrying a bulk commodity, as coal or wheat, to a specific destination and that after unloading returns to the point of origin ready for another load.

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Etymology

Origin of unit train

First recorded in 1960–65

Example Sentences

A little over a year ago, a unit train carrying 7.7 million liters of shale oil in 72 Class 111 tank cars from the Bakken fields of North Dakota derailed in Lac-Mégantic Quebec. 

From Forbes • Aug. 19, 2014

Beginning with one unit train in 1964, the road now runs 550 a month.

From Time Magazine Archive