A pipeline is an option on a locational spread, and the spread most of these are written on is Brent against WTI — which is a logistics spread, not a quality one. WTI settles inland at Cushing, Oklahoma, with no water access of its own, so when barrels cannot get out of the Midwest the discount widens until something moves them. The US export ban, lifted in December 2015, blocked that adjustment for years and decoupled the two benchmarks outright: infrastructure and regulation set the bound, not economics. What follows is the physical side of that arithmetic. Across the whole reported history the Gulf Coast sent the Midwest about 42 million barrels a month against 16 going the other way — imported crude landing at the coast and moving inland. In the latest reported month those figures are 24 and 50. The corridor has reversed, and pipe built to carry foreign barrels north now carries domestic barrels south. Read the modes separately: the substitution between them is usually where the story is.