Compliance and operational variance: when plans meet reality at sea

Even with credible models and reliable tools, the gap between recommendation and reality can be wide. This insight explores how shifting weather, currents, schedule pressures and operational priorities push vessels off optimum, and why even small, repeated deviations can swallow a meaningful portion of the predicted efficiency gains.

Even when the data collected and used by maritime organisations is correct, and the tools used are reliable, compliance remains a challenge. In the context of voyage optimisation, this means how closely the recommended propulsion or route settings are followed onboard.

In simple terms, it means how closely the plan made by the optimisation system matches what actually happens during the voyage. For example, changing the suggested target speed, power setting, or RPM requires diligence, with updates every 2 hours or more. Since speed is typically controlled indirectly via RPM rather than set directly from the bridge, maintaining the desired speed requires continuous fine-tuning. Weather and currents further drive the need for ongoing adjustments, as even minor variations can push a vessel away from its optimal position.

As Stavros Paschalakis, Chief Technology Officer at DeepSea Technologies, explains, “when users adhere to the instructions, they do unlock savings. The problem is that sometimes they are not able to follow them.”

If conditions ease or change again, maintaining the same RPM could result in the vessel’s speed increasing above or decreasing below the initially intended level. This constantly changing environment requires equally constant adjustments to propulsion settings, which can involve manual crew involvement.

While following recommended speed profiles can deliver the predicted fuel savings, operational factors often lead to deviations. When vessels reduce speed to save fuel, factors such as weather, currents, and operational pressures can prevent the expected fuel savings or arrival times from being realised.

Even small deviations, repeated over the course of a long voyage, can add up. The difference between near-perfect and moderate adherence to a speed profile can account for a meaningful portion of the expected efficiency gains.

This can lead to inefficient operating approaches, such as sprint and loiter, in which vessels speed up early to maintain schedule certainty, only to arrive ahead of schedule and wait at anchor.

These priorities matter, as Erkut Denizci, Fleet Manager at ITM, explained, “If you leave the captain or chief engineer on his own, for sure, vessel performance would not be the number one priority. This is not because they don’t value it, as there might be other priorities onboard the vessel other than voyage performance.”

This is an operational reality, as crews have many competing demands, which means optimisation is often driven more strongly from ashore than from on board routine. For many operators, the gap between expected fuel savings and those they achieve in practice is therefore not primarily a question of technology or approach, but of adoption and compliance.

While advisory optimisation systems can provide guidance, they cannot guarantee that recommendations are followed. As a result, measuring compliance is becoming a useful indicator of optimisation performance.

Adding to constraints are the physical and technical limits of existing vessels, which can make it more difficult to achieve optimisation targets. Mohammed Rasi Areechola, Energy Management & Efficiency Officer at Zodiac Maritime, identified this, stating, “there is definitely friction. Most of the vessels are very old, and from a design perspective, the ships are not that efficient.”

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