Multi-Objective Ship Route and Speed Optimization Under Time-Varying Marine Environments Based on NSGA-II

Efficient ship voyage planning under time-varying marine environments is important for reducing fuel consumption, improving operational efficiency, and maintaining navigational safety. This study proposes an NSGA-II-based multi-objective ship route and speed optimization method that jointly optimizes intermediate waypoint positions and segment speeds. A three-objective framework is developed to minimize fuel consumption, voyage time, and a navigational safety index. Static navigational data are used for feasibility checking, while time-varying wind, wave, and current fields are matched with route segments according to their positions and sailing times. An Extra Trees-based fuel consumption model and a multi-factor safety index evaluation model are embedded into the segment-level evaluation process, and joint waypoint–speed encoding, grouped genetic operators, and constraint handling are incorporated into the NSGA-II framework. A case study on the Busan–Ningbo route shows that the proposed method generates a well-distributed Pareto non-dominated solution set and reveals clear trade-offs among the three objectives. The TOPSIS-based recommended route achieves a fuel consumption of 43.468 t, a voyage time of 34.599 h, and a safety index value of 0.830. Compared with the A* baseline route, the proposed method reduces fuel consumption, voyage time, safety index value, and route length by 5.08%, 3.52%, 20.61%, and 5.65%, respectively. Comparisons with the original NSGA-II and CMOPSO further show that the proposed method improves Pareto solution quality and route smoothness among the multi-objective optimization methods. Results from two representative oceanic route scenarios further demonstrate that the proposed framework can generate feasible Pareto solution sets and recommended routes under different voyage conditions. These results indicate that the proposed method can provide feasible, smooth, and balanced route–speed solutions for voyage optimization under complex marine conditions.