Optimization of resources in towage services by simulation modeling method

The efficiency of the organizations that provide towage services in ports is important in terms of service quality. Factors affecting the efficiency can be listed as ship traffic density in the port area, number and bollard pull of tugboats, size of the port area, response time to service request, parking locations of the tugboats, meteorological conditions, currents etc. On the other hand, due to the high costs of tugs that are the sources of this service, organizations face high investment costs. The insufficient number of tugboats that the organizations have will increase the waiting times of the ships and decrease the service quality. Having more tugboats than necessary will increase the investment and operating costs, and decrease the efficiency as a result of tugboats being idle. Due to these reasons, it is necessary to determine the optimal resource utilization by considering the variables of the port area to be served. In this study, it is aimed to develop a simulation model for determining the efficiency in resource utilization in port towage services. In addition, it is aimed to present the mathematical equations of the relationships between the variables that affect the service level. ProModel software was used for simulation modeling. For the determination of statistical distributions to be used in the model, goodness of fit tests were applied to the ship operation data of three different ports in Turkey. Following the model building, experiments were generated from various combinations of independent variables. Simulations of the experiments were carried out and statistical analyses of the obtained results were made. Correlation test, normality tests and multiple linear regression analyses were performed. In addition, the findings were interpreted by visualizing the simulation results with the help of graphics. According to the number of ships and the port area sizes, the minimum numbers of tugboats in which the organizations should have were determined. For various situations in which the number of ships varies, the determinations were made regarding the maximum port area sizes in which the organizations can serve with the tugboats that they have as resource. The performance measures taken into account while making these determinations are the waiting times of the ships while they are outside the terminal and in the terminal. The results of the study are expected to serve as a decision support tool for service providers and the Administration in relation to a variety of situations that consists of different conditions and constraints.