Judged by unit of weight, ship and rail transport in particular are highly energy efficient. Financial considerations force shippers to pack as much as they can into their cargo containers, whether they're being carried by ship, rail, or truck, and to ensure that they rarely make a return trip empty.But how often do containers actually return non-empty? That doesn't always seem possible—when food's being shipped to a city, it's not like there's anything to bring back, is there? And surely when you transport bananas on a container ship, you have to refrigerate them, which in turn uses more energy per banana than a short car trip might. I guess the moral is that this stuff is complicated, and the best way to reduce "food miles" would be a labeling system (which Bennett discusses) or—it's turning into a refrain!—a carbon tax.
And because of their size, container ships and trains enjoy impressive economies of scale. The marginal extra energy it takes to transport a single bunch of bananas packed in with 60,000 tons of other cargo on a container ship is more than an order of magnitude less than that required to move them with a couple hundred pounds of cargo in a car or small truck.