The vehicle round trip model addressed by an analytical queuing network

Maritime container terminals have received great attention from the OR-Simulation communityin the attempt to analyze and optimize resource allocation policies and activity scheduling rules under uncertainty. Discrete-event simulation models, which are particularly fit to reproduce complex features within specific subsystems, may be combined with queuing network models to provide average performance metrics of the system as a whole. Here a queuing model and an analytical solution is proposed for the vehicle round trip process: containers are picked-up from one subsystem and set down in another by man-guided straddle carriers (SCs) that travel back and forth between the quay-stations and the yard-stations. Under the assumption that the fleet of circulating SCs corresponds to the customer population, a closed queuing network model for the vehicle round trip process arises. The suitability and effectiveness of using analytical queuing approximations to get reliable results on quantitative performance metrics such as terminal throughput and vessel sojourn time is investigated. Numerical experiments are carried out with respect to a container terminal of pure transshipment. Discussion of some encouraging results, as well as other less encouraging ones, provides some guidelines on future development and/or suitable adaption to container terminal logistics of the large body of techniques and algorithms available nowadays.