Berkley [6] developed simulation models to determine the minimum number of kanbans in achieving a desired production rate for tandem queues. The models were further modified into a two-card kanban controlled system [7]. In the findings, it was emphasized that tandem queue models was not equivalent to two-card kanban controlled systems, especially in the case where processing stations were not located closely together, in which material handling occurs periodically such as in job–shop environments. Berkley [7] concluded that the optimal number of kanbans can be determined only at trade-offs between the costs of frequent material handling and the benefits of lower WIP levels.