A vessel scheduling problem model considering multi-waterway assignment, anchorage queueing, and berth allocation

• Main Author: Magno, Darlyn Jasmin A.
• Format: text
• Language: English
• Published: Animo Repository 2022
• Subjects: Shipping; Scheduling; Operations Research, Systems Engineering and Industrial Engineering
• Online Access: https://animorepository.dlsu.edu.ph/etdm_induseng/7
• Institution: De La Salle University

The maritime sector is the focal and more practical transportation mode of bulk goods as sea freight services have considerably lower transportation costs in terms of long-distance service with high load capacity. The trade of goods supports global economic development, and thus follows the nation’s Gross Domestic Product (GDP). Any delay brought by bottlenecks in the port operations due to limitation of port resources affects its efficiency and the country’s trade competitiveness. Additional resources follow a huge investment to increase the efficiency of the port terminals. As delay plays a major role in port efficiency, such propels various researches regarding port scheduling to minimize the total completion time given the limitations in port resources. In port operations, a vessel undergoes four (4) key stages such as the inbound passage in the waterway, anchorage queueing, berth assignment, and outbound passage. Based on the existing literature, these stages are often resolved independently neglecting the element of interdependence amongst the stages. That is, a bottleneck in the berthing stage affects the traversing vessels in the waterway, the vessels waiting in open waters with respect to vessels’ Estimated Time of Arrival (ETA), and the number of vessels waiting at anchorage. Multi-waterways with the consideration of safety distance were not also explored as ports tend to divide territorial waters into several fairways to handle multiple simultaneous vessels while maximizing their natural resources (territorial waters). Furthermore, to the best of the author’s knowledge, the anchorage stage is not included in the system analysis of existing studies. Based on the limitations of the present literature, a mathematical model was developed to minimize the total completion time of vessels under schedule by considering multi-mode waterways assignment, waiting time in anchorage, and berth allocation while exploring traffic capacity, anchorage capacity, and berth spatial constraints. The mathematical model was formulated and translated into programming language using Python accompanied by Gurobi Optimizer. A base run for a small-scale problem of 10 vessels was conducted to validate the formulated model, and the results showed that the vessels are not allowed to start if the waterway, anchorage, and berth are concurrently busy showing the interdependence of each stage. The waterway that is most utilized is the one with a shorter travel duration but with smaller traffic capacity in both incoming and outgoing passages. Once anchorage was reached, the vessel is either assigned to an eligible berth, concerning spatial capacity, or waiting in anchorage. It is observed that the queueing policy is sorted according to the length of vessel time window, thus, vessels with lower cubage are prioritized as such only incur shorter service time. The model was then tested on up to 50 vessels, 4 waterways, and 15 berths to evaluate the capacity of the model to solve large-scale problems. Furthermore, a case study was performed using Port of Manila data, and the results showed a decrease in completion time by 38%. Given an average of 9 time periods or 270 minutes, the Port of Manila can handle 19 more vessels with the same planning horizon or equivalent to an increase in time efficiency of about 39%. Eight (8) scenarios were established to develop an optimal set of policies for each stage. Scenario analysis showed that utilization of waterways with the same capacities and travel duration comprised longer completion time by 41% than waterways with different capacities and travel duration. As to anchorage queueing and berth allocation, scenarios under First-Come-First-Serve (FCFS) policy showed higher idle time in open waters by 13% and higher waiting time in the anchorage by 3% rather than the scenarios under Shortest Time Windows Length (STW) queueing rule. Lastly, waiting time policy variation in anchorage (unlimited waiting time and limited waiting time) showed no substantial impact on the completion time, however, the limited waiting time policy ensures that an eligible berth shall be assigned within a defined period which provides better managerial implication to port operators. For the interactions of the three factors (waterway and anchorage, waterway and berth, and anchorage and berth), there was no significant effect on the total completion time based on the computed p-values.