COA transportation is not about selecting the best voyage, but about systematically fulfilling obligations under strict constraints and a volatile market.

In maritime practice, Contracts of Affreightment (COA) establish a fundamentally different decision-making framework compared to spot transportation. Here, the question is not about choosing the “best” voyage from available options. Instead, it becomes: how to most efficiently execute a predefined volume of transportation obligations.

A COA contract defines a framework within which flexibility is inherently limited: fixed cargo volumes, defined transportation periods or lifting schedules, and strict performance requirements, where failure leads to penalties. As a result, optimization transforms into a planning problem under obligation, rather than a search for opportunities.

What Makes COA Fundamentally Different

In scenarios such as Sole Cargo, operators can select cargoes, combine them, or even reject certain options. In COA, this flexibility does not exist - cargoes are mandatory. Each contract generates a sequence of liftings - cargo parcels that must be executed within defined time constraints.

This results in a multi-layered problem where it is necessary to simultaneously fulfill all contractual obligations and maintain an efficient and balanced fleet operation.

The Problem Marine Solver Addresses

The COA module in Marine Solver is designed specifically for this environment where obligations are fixed, but the way they are executed remains subject to optimization. The system matches vessels to liftings based on fleet positions, constructs optimal sequences, and integrates these decisions into the overall fleet deployment model.

Spot Cargoes as Part of the Model

Repositioning legs often create underutilized time gaps. In Marine Solver, such gaps are treated as an integral part of the optimization structure. The system allows spot cargoes to be integrated into the chain prior to liftings with full preservation of control parameters (laycan tolerances, compatibility, fuel choices).

Cargo Splitting and Operational Flexibility

The model supports splitting cargo parcels into parts and distributing them across multiple vessels. This enables alignment with actual fleet positioning, cost reduction, and improved system resilience, reflecting real-world execution adaptability.

Unified Cost and Constraint Framework

The COA module incorporates all key voyage cost components: fuel, ports, canals, waiting time, EU ETS, SECA zones, and CO₂ emission constraints in line with IMO requirements. This ensures solutions are economically and environmentally consistent.

Results and Computational Performance

The system provides visual graphs, detailed operational tables, and financial metrics. Even for complex problems - e.g., 20 vessels, 8 liftings, and 20 candidate spot cargoes - the system delivers a complete solution within approximately two minutes.

Conclusion

By integrating contractual obligations, fleet positioning, and market opportunities into a single model, Marine Solver enables the transition from reactive management to proactive optimization of COA portfolios.

Complementary optimization tools:
Learn how Marine Solver handles individual spot voyages in our Solo Cargo Module or how to optimize multi-parcel shipments with the Part Cargo Module.