Optimal Capacity of Port Loading Facilities

Route changes and delays owing to such factors as adverse weather make it difficult to predict the exact arrival of ships or barges in a port. In choosing the capacity of loading facilities in a port, one must consider that there will be many times when the facilities will be unused and many times when cargo vessels must wait a substantial time before they are serviced. The choice of capacity of port facilities when arrival and service times are random is considered here. Queuing theory can be applied to determine the average waiting time for an individual cargo vessel as a function of the arrival and service distributions, the capacity of the terminal facility, and the arrival rate. To save waiting time for a vessel, the terminal capacity must be expanded. The optimal capacity of a loading facility is determined by trading off the additional capital cost of a dock against the value of the vessel time saved. Estimates are made of costs and savings incurred by investing in new facilities. The effects of seasonality in traffic and speeding the service rate are also considered.