Infrastructure investments tend to reinforce the existing efficiency of the inland
transport system in which long distance is dominated by rail and where limited, if
any, inland barge services are possible. The new heartland corridor linking the
terminals of Norfolk to the Chicago hub is a salient example. The benefits of doublestacking
were expanded with double (or triple) tracking, and the setting of inland
load centers servicing their respective market areas. This also permitted the setting of
large-scale intermodal rail terminals because such economies of scale were feasible.
Thus, North American inland terminals tend to service large market areas.