Ensuring the safety of autonomous shipping

In December 2024, DNV announced the release of the Autonomous and Remotely Operated Ships (AROS) notation. The objective of the notation, which took effect from 1 January 2025, is to provide a framework for how autoremote vessels can achieve equivalent or higher safety compared to conventional vessels.

Multi-structured AROS notation

The AROS notation is broad and comprehensive. The scope of the rules is to define systematics and functional and procedural requirements for autoremote vessels and systems used on board and off-ship. This extends to the remote operating centre and the connectivity needed for autoremote vessel operations. 

Autonomous shipping can be defined by three dimensions: location of control, [degree of] human involvement and degree of system independence. DNV divides each of these dimensions into four broad categories – remote control, decision support, supervised autonomy and full autonomy  – which can be controlled from various locations. These categories can be applied to different functional areas: navigation, engineering, safety and operations.

Defining autonomous shipping in different ways

These dimensions and categories define the concept of autonomy in different ways. Remote control refers to vessels where operations are carried out at locations other than the vessel, while decision support refers to on-board systems which act like a “co-pilot”, analysing information and generating advice which is fed to an operator, who can then decide whether to act on this advice or not. 

While remote control and decision support will always have human beings at the centre of the decision-making process, this begins to deviate significantly with the other categories. Supervised autonomy has similarities to decision support, but the system can act and make decisions without waiting for acknowledgement from a human. Nonetheless, a human operator is informed about the system’s intentions in real time and can stop or override when necessary, something which only happens in exceptional circumstances in the case of full autonomy.

“The AROS notation acknowledges these different modes of operation, and these are central to its structure,” says Mariah Kurtinaitis Joukes, Autonomous Shipping Senior Engineer at DNV.

Advancing autonomous shipping

While some features of autonomy have been present in shipping for the past decade, their implementation has rapidly advanced in recent years. Several pilot schemes have been tested for unmanned, fully autonomous vessels, while decision support systems are increasingly prevalent on conventional vessels. While the trend is undoubtedly moving towards more autonomy, the motivation and benefits vary depending on what kind of system is in place.

“Unmanned vessels provide a lot of freedom,” says Are Jørgensen, Senior Principal Engineer, Digital Ship Systems at DNV. “You can take a vessel that is 80 metres long and reduce this to 20 metres by removing accommodation space and everything else associated with the crew. This reduces risk and enables leaner designs, so this has a lot of appeal for shipowners.

“At the other end of the scale, decision support systems are already helping to reduce the workload and stress levels of on-board crew and helping them to make better and safer decisions.”

Environmental benefits of autonomous shipping

Increased autonomy can also lead to environmental benefits, a crucial consideration in a maritime industry exploring all possible routes to decarbonization. Decision support systems are already helping ship operators with route and speed optimization, maximizing the efficiency of vessels. Vessels with supervised autonomy and full autonomy can take this even further.

“Autonomous vessels and systems enable you to take many more parameters into account when plotting a route,” says Jørgensen. “For example, this can help you achieve just-in-time arrival at port. If a ship operator knows that port entry will be delayed, they can take a longer route where, for example, there is more of a tailwind. This can also work for optimization of fuelling, and many other things, like considering the impact of the weather upon arrival time. The sky is the limit.”

Safety at the heart of the AROS notation

At the heart of the AROS notation is the need to verify autonomous vessels as being as safe or safer than conventional vessels. “While humans are often the cause of incidents on conventional vessels, they can also prevent smaller incidents becoming catastrophes,” says Jørgensen. “So, in order to improve safety, we need the autonomous systems to be very robust and resilient.

“This is where we are trying to get to, and it is central to the framework that we have established with the AROS notation.”

Lightly regulated autonomous shipping

Autonomous shipping is still a lightly regulated space. IMO is currently addressing this by developing a code for Maritime Autonomous Surface Ships (MASS) – a definition which aligns with DNV’s definition of “autonomous and remotely operated vessels”. MASS is expected to be voluntarily applicable from 2025, but not mandatory until 2032. Without regulation, the development of autonomous vessels has up to now been based on a broader, more abstract risk-based approach, applying guidelines from IMO Resolution 1455.

“This basically means that if there are no existing rules to follow, you then need to describe what you want to do, identify the associated risk and then take actions to de-risk,” says Joukes. “At DNV, we have been acting as a third-party verifier on a number of autonomy projects, based on this risk-based approach, and this has given us important knowledge which we have used to structure the AROS notation.” 

Building on the DNV guidelines

“There are two parts to the notation,” says Joukes. “One part is that it recommends clients to follow a risked-based process, which has already been described in DNV guidelines for autonomous shipping, and the second is based on functional requirements.”

For this risked-based element, the AROS notation builds on the process-orientated DNV guideline (DNV-CG-0264) for autonomous shipping, which has been in place since 2018. Importantly, this contains process descriptions for both concept qualification and system qualification. Both are systematic, risk-based assessments used in the development of novel technologies that ensure these technologies are safe, reliable and ready for market. 

According to Jørgensen, going through these processes is a central part of the journey for developers of autonomous vessels wishing to be awarded the AROS notation. “While the notations apply some specific requirements, the nature of autonomous ships means there are many novel concepts which cannot be fully covered by requirements, particularly as we expect many innovations and technological developments in the future. This is why the risk-based approach is such a key part of the notation. It is not prescriptive in nature and is deliberately broad.”

Using previous experience to build the AROS notation

Based on previous experience in applying the risk-based approach, three things have been fundamental in creating the AROS notation.

Firstly, some patterns have emerged regarding functionality, and this has been very important in gaining a better understanding of how autonomous ships operate.

Experience has also taught the project team to carry out a better and more structured risk analysis. This led to more focus on the follow-up of identified risks to ensure that these are mitigated in a good and traceable way.

Identifying the need for a flexible approach has also been crucial. This creates the option for DNV to carry out a safety evaluation of pilot test phases in the overall process. “In some cases, the concept owner or system supplier doesn’t really know what they’re going to do until they have tried and failed a bit. This allows them to try and fail in a safe way,” says Jørgensen.

Development of key functional requirements for autonomous systems

Taking the knowledge and experience of working on autonomous projects, and identifying key patterns, DNV has developed some key functional requirements for autonomous ships, the second main pillar in the AROS notation. These complement the risk-based approach by drawing some lines in the sand with some fundamental rules.

“These functional requirements vary, depending on each system and which kind of notation is being sought,” says Joukes. “Generally though, this includes the expectation that vessels holding the AROS notation will be able to respond to abnormal events, and the requirement that vessels can monitor and respond to incidents which can result in harm to people, the environment or the vessel itself.”

Like the risk-based approach, these rules are expected to evolve in step with developments in the autonomous shipping space.

Safety at the heart of DNV’s outlook on autonomous shipping

DNV has been a pioneer in autonomous shipping for a number of years, with key involvement in flagship projects like Yara Birkeland, Reach Remote and Ocean Infinity. Like everything, DNV’s continuing involvement in the space is primarily driven by the goal that the maritime industry continues to evolve and innovate in a way that is safe and secure. 

“As a class society we have no desire to push autonomy for the sake of autonomy,” says Joukes. “But if our customers are going in that direction, we should be able to help them and make sure that this is done in a safe way.

“That is our mission in class.”

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