The inbound/outbound cargo imbalance is significant but not unique to Alaska. Cities in the Lower 48 experience the same imbalance, with more cargo coming into the city than goes out. (Plus, outgoing cargo tends to be LTL.) With some effort, you can exploit this fact to reduce shipping costs.
A lot (if not the majority) of the semis you see on highways pulling two or three trailers are actually deadheading empty trailers to where they're needed. The same goes for flatbed semi-trailers stacked on top of each other.
It's not limited to semi-trucks. Trains pulling empty flatbed cars and boxcars are also deadheading those, usually mixed in with actual cargo.
