Study On The Enlargement Of Container Ships Considering The Scale Economy Of Port And Shipping System

In the past 30 years,the trend of enlargement of container ships is very obvious,because shipping companies hope to achieve the scale economy of international trade transportation by using large ships,and obtain the largest operating profit in the market environment of increasing freight demand and long-term low freight rate.However,when shipping companies promote the large-scale container ships,they often ignore the extra cost to deal with the large-scale ship terminal companies,as well as the loss of transportation convenience and the decline of service level suffered by shippers due to the large-scale ship.In fact,the large-scale container ships not only bring the scale economy to the shipping companies,but also bring a series of scale diseconomy effects to the terminal companies and shippers.If we only consider the scale economy of shipping companies and ignore the scale diseconomy of terminal companies and shippers,we may reduce the overall interests of the supply side of container transportation,because in the long run,the construction and operation costs of terminal companies increased in response to the large-scale ships will eventually be transferred to the shipping companies and shippers.However,the decline of the service level of the shippers will inevitably bring negative impact on the whole international container transportation market,resulting in the loss of the whole social welfare.Therefore,it is necessary to consider shipping companies,shippers and ports as a whole when studying the large-scale container ships.The sum of shipping companies' transport costs,port expansion costs and external costs caused by the inconvenience of shippers should be taken as the total cost of the supply side of the foreign trade container shipping market.This paper first analyzes the mechanism of scale economy and scale diseconomy brought by the large-scale ship to the shipping companies,ports on the supply side and shippers on the demand side of foreign trade container shipping,and reveals the scale economy and scale diseconomy that can be realized by shipping companies under different freight demands,and the scale diseconomy(mainly expansion)encountered by ports in response to the large-scale ship shipping The investment cost of building terminal capacity)and the increased transportation cost(mainly the increase of cost,time and uncertainty caused by transshipment)caused by the large-scale ship to reduce the number of ships attached to the port.Secondly,based on the relationship among the three above,the optimization model of the hub and spoke empty and load container liner route is established.Under the condition that the OD flow of containers between ports is known,the route plan and container transportation plan using different sizes of container ships are determined with the lowest total cost of container transportation as the objective.The total cost in the model includes the cost of the shipping company involved in the transportation of all containers from the starting point(O)to the destination(D),the cost of the terminal company(terminal construction and operation),and the money,time and risk cost of the cargo owner.Under the assumption that the original influencing factor is ship size,the single container transportation cost corresponding to all possible candidate ship types can be obtained by solving the model,and the candidate ship type corresponding to the lowest single container cost is the best ship size in theory under this OD flow.Then,by simulating the future transportation demand and setting various od flows,and solving the model accordingly,we can get the theoretical upper bound of ship large-scale in the foreign trade container shipping market under different transportation demand.