During the development of the model, some obstacles were faced concerning modeling complex operations
performed and decisions made in the port. A brief description of some of these obstacles is now introduced as well
as how they were resolved.
In the simulation model, it is assumed that the three different means of container transportation arrive to the
system already loaded with no regard to where or how these containers came from. In order to do that, a ship, train
or truck is initially created as one entity until it reaches the port. At that instant, it is duplicated to produce the
amount of containers that it should carry and these new duplicates are assigned a new entity type to make the model
recognize them as containers. The Separate Module in Arena was used to perform the duplication.
In order to add fidelity to the model and to reduce complexity, an initial amount of containers was assigned to the
Container Yard before the first event occurs. This was done by creating an external source of containers and sending
them to the Container Yard without travelling time.
In order to make the transporting entity wait until all the containers have been unloaded or loaded, a counter was
assigned to count all the containers that are being processed after drop off. The containers are then held (via Hold
module) until all required entities are there.
To be able to distinguish between the different arriving and departing containers, their mode of transportation as
well as the different ship types and sizes, Assign modules are used throughout the model to assign specific entity
types as well as specify the required attributes to the entities.
Yard trucks were modelled as Transporters to simulate their movement around the port from the ship to the
container yard and vice versa, and also from the container yard to the train and vice versa. Transporters in Arena are
resource types that realistically represent a vehicle movement including its speed and distances between pick up and
drop off locations.