Vehicles have different cargo unit capacity shown on the table below.
The cargo unit transportation cost ci then is the vehicle operation
cost Ci divided by the vehicle capacity ei . ci = Ci / ei = ( ai d +bi
) / ei. Under these assumptions for distances below 100 the truck is
the most cost effective mode, then up to a certain threshold the train
and, later, the feeder vessel. After a certain distance the most cost
effective is the ocean vessel.