Operating parcel transshipment terminals: a combined simulation and optimization approach

Parcel transshipment terminals are complex systems that consist of automatic conveyor networks and manual handling activities. Therefore, using discrete-event simulation to evaluate a terminal seems obvious and is often used in the literature. On the other hand, mathematical optimization represents a powerful method that has been successfully used to solve a wide range of logistical problems. Simulation allows for modeling logistics systems with almost unlimited complexity very close to reality, but finding the best system configuration is difficult and time-consuming. In contrast, mathematical optimization has the ability to make complex decisions and find (near) optimal solutions. Real-world logistic systems, however, can only be solved on a lower level of detail without stochastic behaviors. In this article, we present a modeling framework for the operational planning of a transshipment terminal that closely links both methods in order to make use of their complementary advantages. Thus, we are able to handle a large number of decisions, such as (un)loading dock and sorting destination assignments, and consider complex automatic sorting systems as well as manual handling activities with stochastic elements. The approach is evaluated on the example of a parcel transshipment terminal using three different input data scenarios.