Truck traffic proliferates because it's still profitable but we are running down our supplies of petroleum. As we keep burning up our fossil fuels at an accelerating pace, thanks to industrialization around the world, the price of a gallon of diesel will rise to the point that this crazy level of trade and transport will get too expensive to be profitable. Barge and train transport will become much more important, and distances goods are carried will be looked at in the cold hard light of day (like we'll start shipping apples to New Orleans from Tennesse rather than Oregon). Let the price of fuel rise to what it really should be, resisting the overwhelming urge to whine and insist cheap fuel be our birthright.