April 28, 2016 | Chicago Magazine | They could not look more ominous. The long coal-black tubes announce themselves by their distinctive shape and color, their markings too small to read from the street. The 30,000-gallon tank cars roll, sometimes 100 at a time, in trains of up to one mile in length. Their cargo? Crude oil—as much as three million gallons per train. Nearly all of it is light sweet Bakken crude, a type that is particularly explosive. In whole, these trains constitute likely the biggest, heaviest, and longest combustibles to ever traverse America, and they do so routinely. More pass through Chicago than any other big metro area. Their blast potential has earned them a terrifying nickname: bomb trains.