Queuing theory has been regarded as an important analytical tool for solving congestion problems. It can be used to estimate certain important parameters, such as average waiting time of ships, average queuing length, average number of ships in the port, and average berth utilization factor (closer to the actual values).
Jansson and Shneerson (1982) stated that ships arrive to a port mostly at random and hence have varying demands for port resources. Therefore, the short-term demand for port services fluctuates. For example, it is possible that during one week all resources will be occupied and the ships will be in queue; and during the next week there will be no ships at all in the port. As a consequence, the supply of port services or, in other words, the service time of ships is also highly variable. Hence, in order to determine optimal port capacity, it is necessary to analyze the trade-off between the two objectives of a high level of utilization of port facilities and a low chance of delay for port users.