FedEx's Reed agreed that it's not easy to add facilities in heavily populated areas

Cunningham also noted that highway congestion is one of the factors driving rail growth. In order to keep up with growing demand, railroads will have to add capacity—and that is enormously difficult, he told session attendees. "The issue is infrastructure and how to pay for it," he said. One problem is that the places where additional infrastructure is needed most are the places that have the least available space: fast-growing metropolitan areas. Even where railroads can expand, the high price—a new intermodal facility can cost $200 million—and the lengthy approval and construction processes mean that it will be a long time before any rail projects can have an impact on capacity.

FedEx's Reed agreed that it's not easy to add facilities in heavily populated areas. "You just don't plop down trucking facilities in the L.A. basin or the Northeast anymore," he said.

Congestion is one reason O'Neal predicts a future in which distribution centers will have to operate 24 hours a day, seven days a week to ensure that freight both arrives and departs on time. "Every major institution that ships or receives is going to have to go to a 24/7 operation, have better driver facilities and amenities, develop contingencies for service delays, and put realistic expectations on the table," he said.