## 7 Conclusions and Future Research  
In recent years, cruise ship construction orders have increased significantly, and the amount of hazardous waste generated during the cruise ship construction process has also risen. This study addresses the critical challenges associated with hazardous waste management in the context of cruise ship construction. By developing a novel reverse logistics network operation scheduling optimization model, we integrated considerations of cost, efficiency, safety, and environmental sustainability. The key findings and contributions of this research are summarized as follows. In the context of hazardous waste recycling during the cruise construction process, this paper proposes a reverse logistics network operation optimization model that embraces a holistic HSE perspective, integrating cost, efficiency, and risk considerations. The model employed fuzzy operation time windows to reflect safety satisfaction and leverages the DCSA method based on Levy mutation to derive a green, efficient, and safe scheduling scheme. The objective of the model was to optimize the allocation of transport vehicles, path planning, and risk assessment to improve operational efficiency and safety. To enhance the realistic nature of the model, this paper considered factors such as vehicle load, transport cost, loading time, and risk weights, ultimately achieving better transport efficiency and safety. To address the problem, this paper designs a three-phase approach: firstly, the allocation of transport vehicles to various task centers; secondly, route planning; and finally, the integration of risk satisfaction indicators for a comprehensive assessment. By comparing with the cost-only scenario, the results show that although cost-oriented scenarios may provide economic benefits in the short term, they often ignore risks that could lead to long-term consequences. The results of the comprehensive assessment indicate that the proposed model offers a more sustainable approach to hazardous waste management, emphasizing the importance of incorporating safety considerations into operational planning. The model presented in this paper still has some limitations, focusing mainly on the scheduling of transport vehicles for a single hazardous waste pickup and not exploring the equity of risk for multiple hazardous waste types. Given the diverse safety and health impacts of different materials, future research could explore the risk equity of transporting multiple hazardous waste types within the same network to further enhance the applicability and comprehensiveness of the model. Based on the HSE management requirements of shipyards, future research could be extended to investigate a wide range of factors that affect logistics and HSE performance. These factors include the cost of training workers to handle hazardous waste and the availability and reliability of safety equipment. In addition, vehicle breakdowns or damage resulting in transport interruptions are worthy of further study. These factors can significantly affect cost volatility, transport accessibility and timeliness. Exploring these aspects will contribute to a deeper understanding of safety risk management and operational efficiency in shipbuilding environments. Conceptualization, H.L. ; Methodology, W.Z. ; Software, W.Z. ; Validation, H.L. ; Formal Analysis, H.L. and W.Z. ; Investigation, H.L. ; Resources, J.Y. ; Writing--Original Draft Preparation, H.L. ; Writing--Review and Editing, J.Y. ; Visualization, H.L. and W.Z. ; Supervision, J.Y. ; Funding Acquisition, H.L. and J.Y. All authors have read and agreed to the published version of the manuscript. This research was supported by the Ministry of Industry and Information Technology (China) for Research on the Key Technology of the High-Tech Ocean Passenger Ship Construction Logistics Collection and Distribution System [MC-202009-Z03], and Research on Cruise Engineering Project Management Technology [MC-201616-C12-04]; and the Chinese Government Scholarship by the China Scholarship Council (grant no.