Another example of future research area is transshipment and
its associated costs. Ignoring transshipment might result in suboptimal
or infeasible solutions. In multimodal network design, transshipment
are these operations at a multimodal terminal to shift
flow from one mode to the next (Vis & de Koster, 2003). It fundamentally
depends on technology and the equipment used to transfer
operations. Studying feasibility, capacity, operation time and
cost of transshipment in network design problems play a crucial
role in multimodal transportation problems, especially with more
than two modes. Ishfaq and Sox (2010), Ishfaq and Sox (2012) include
both transshipment costs and a fixed cost to reflect modal
choice in multimodal hub network design. They call this modal
connectivity cost. The authors show in both papers that in comparison
to over-the-road structure, design of multimodal networks is
sensitive to the network parameters, especially to the cost ratio
of transportation modes and this modal connectivity cost. Better
insight in the cost structure of intermodal transport chains is one
way to find necessary and effective policy actions for realizing
modal shift, which needs more research attention.