Rivers are by far the most efficient means of moving goods and people from place to place, but navigable rivers don’t flow everywhere. For such non-fluminous regions, there are railroads. At roughly one-quarter the operational cost of roads, there is no better (non-river) means of shuffling things about, particularly in bulk.
A dozen independent factors are making rail transport more important in the world to come. Vast reductions in global trade will limit what economic exchanges that survive internally. Mexico lacks good ports, so most goods need to be moved via rail. Canada’s breakup would generate a rail renaissance in the Prairie Provinces and throughout the Upper Midwest. Coal’s return to dominance in Europe and Japan will require it to be transported en masse by both river and rail. Shale’s ongoing rise has overloaded pipe transport options, and so rail is picking up the slack.
For more on the remaking of the global system, see Chapters 8, 12 and 13 of The Accidental Superpower.