Transshipment becomes more critical in the presence of cut-off
times and when synchronization of the system plays an important
role in on-time delivery of time-sensitive products. Andersen,
Crainic, and Christiansen (2009b) seem to be the only one taking
synchronization into account. They extend the work of Andersen
and Christiansen (2009) by including the synchronization within
the system and with the neighboring systems. They conclude that
by more collaboration and integration of transportation systems,
significant improvement in performance can be achieved. In order
to have a synchronized transportation system, studying transshipment,
its conditions, and costs offers another interesting future
research direction.