iii
Summary
A container distribution network can be seen as the extension of a port deep into the continent: the hinterland. Development of such a network, consisting of terminals and connections, is therefore crucial for the expansion of a port. Developing the network can be done by adding features to the network (‘system design’) or more effectively using the network (‘service network design’). For both design issues one can use a mathematical optimization problem to optimally upgrade the transport system or service. Issues like, determining the location of new terminals, the quantity of equipment to install, on what route to provide services and how to distribute the containers through a physical network, can be solved. The goal is to satisfy the customers in the most cost-efficient way. This transportation problem is the subject of many researches. However, models dealing with intermodal transportation are still limited and are in general based on merged unimodal transportation models. The intermodal networks are more extensive and therefore difficulties arise in solving these models, which are typically mixed integer problems (MIP). The computational efforts needed for solving these problems increases drastically with the increase of the network size. One way to overcome this computational difficulty is to develop more efficient and faster algorithms. Another option is to reduce the size of the model by removing parts of the network of terminals and connections. This research is concerned with developing a selection procedure based on parameters of terminals and connections to make a contemplated selection.
The following research question will be answered: how could an intermodal container distribution network be selected in a generic way?
To answer this question, first, intermodal container transportation is investigated in a literature research. This research contains an overview of models and networks used in other researches. Almost all models make use of the same modeling technique, but vary in complexity. Different features are used to more accurately describe the real behavior of a network, for example, capacity constraints on parts of the network and time-dependent parameters of the model.
The important parameters of intermodal container transport are used to come up with an intermodal container distribution network in a generic way. Parameters like, handling and storage capacities of the terminal, transport capacities of the connections and the related cost of performing these actions, are part of the models proposed in literature.
Since multiple aspects in intermodal container transport are important, the following aspects should be considered in the selection procedure:
The number of modalities served by a container terminal is a logical choice of an aspect to be taken into account. In intermodal container transport the goal is to have several options to transport containers in order to get an optimal transportation solution at a certain time. Having trimodal terminals, serving both rail, barge and road transport, in the network would offer this possibility.
The second aspect to consider is the capacity of the terminals in terms of handling and storage capacity. In intermodal transport containers are transferred from one mode to another. Terminals offering high handling capacities should therefore receive a higher grade in the selection.
Third and last aspect in the selection procedure is the capacity of the rail, barge and road connections between the terminals. In the end, intermodal container transport is all about getting a certain amount of containers from one location to another. The connections should allow this amount of containers flowing through the network.
Abovementioned aspects should all be considered in the selection procedure. However, one of the three aspects could be considered more important than the others. Therefore, weight factors can be applied to indicate their relative differences in importance. In this research all terminals are given a grade for each of the three aspects. The total grade, , of each terminal is based on the sum of
the grades for each aspect times their respective weight factors, as illustrated in the equation below:
total modality modality capacity capacity connection connection
S
S
WF
S
WF
S
WF
Where:
- represents the grade for aspect .
iv
However, this equation is quite abstract. Determining the value of the grades for each aspect is an important and difficult task, especially for the capacity and connections of the terminals. Obtaining reliable and a complete range of data would require an extensive research. In this research the capacity of a terminal is graded using the terminal area and equipment installed. The connections of a terminal are graded using data about the infrastructure of different modalities.
The abovementioned selection procedure is evaluated on a test case of intermodal container transport in the Netherlands. In this country a dense infrastructure of terminals, waterways, tracks and roads exist in order to transport a large amount of containers from the ports of Rotterdam and Amsterdam to the hinterland. Scenarios using different weight factors and network sizes are evaluated. The resulting networks all contained a few ‘core terminals’ having high grades on all selection aspects. The remaining part of the network changed with different weight factors.
Further research towards a terminal selection procedure could be in the direction of incorporating distances between terminals selected in the network. In this way a network with a more consistent density will be generated. In the proposed selection procedure there is no constraint on distances, leading to satellite terminals having large distances to the other terminals in the network. However, incorporating this feature would result in an iterative process: selecting terminals, calculating distances and do the selection again. One must be careful not to make the selection procedure too complex, otherwise you could better focus on developing faster solving algorithms. Furthermore, transport demands could be incorporated in the grading of the terminals, because eventually there must be a need for transporting containers to or from a certain region.
!["O księgach narodu i pielgrzymstwa polskiego A. Mickiewicza", Stanisław Pigoń, Kraków 1911 : [recenzja]](data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACH5BAEAAAAALAAAAAABAAEAAAICRAEAOw==)