A: That East/Eest balances is one source of empty moves, but there are other potential causes.
Shippers tend to favor certain ports for export shipments based on ship rotations. They prefer to use the last port of call for exports to minimize the time consumed on the water. So, for instance, a ship may call at New York first then head for Norfolk, Va., before heading overseas.
There are also issues where volumes fluctuate with ship schedules so railcars can pile up near the ports awaiting their next assignment and need to be moved either to free up track space or for use elsewhere.
There are also differences between international (40-foot) and domestic (53-foot) container traffic patterns. Domestic loads tend to move eastbound from the Midwest to the East, while more loaded international containers move West because imports over the East Coast exceeds exports. — Larry Gross, intermodal shipping consultant