How Digitalisation Will Contribute to Allow Unmanned Merchant Vessels to Become Reality

The creation and implementation of unmanned merchant vessels is inevitable. For the shipping industry unmanned vessels offer great opportunities. Several projects are already underway or have already been accomplished to develop, test and validate vessels without a crew on board. From an international legal perspective, there are certain core issues that are likely to arise concerning the use of unmanned merchant ships. The most urgent question is whether unmanned merchant vessels are regulated by the international law of the sea.

Economic advantages of unmanned merchant vessels

For the shipping industry unmanned merchant vessels offer various advantages, for instance: minimization of harmful emissions, reduction of fuel costs (at 11.000 TEU, e.g., the Emma Maersk, which was until 2012 the largest container ship ever constructed, consumes 14.000 litres of heavy oil per hour), offsetting expected shortage of seafarers in the future as well as a reduction of total operation costs (crew costs today account for 44 % of total operating costs for a large container ship).

Unmanned ships have not yet gone beyond the development and validation phase. However, it is estimated that the first crewless ships will be sailing the seas by 2020, whereby container ships and dry-bulk carriers will probably be the first to forgo crews. Tankers hauling hazardous materials such as oil and liquefied natural gas will probably remain manned for longer, because of the perception that having people on board is safer.

Current projects and developments

To shed some light on the status quo of development, the European Commission has for example co-funded a 3.8 million Euro concept study named “Maritime Unmanned Navigation through Intelligence in Networks” (MUNIN) which prepared a prototype for simulated sea trials to assess the costs and benefits of unmanned shipping and thereby identified the most critical technological, operational and legal factors that may pose obstacles to the operational use of unmanned merchant vessels. At the next level of research and development a project by DNV GL is worth mentioning. The “ReVolt”, a 1:20 scale model of an unmanned short sea-going cargo vessel, fully battery powered with zero-emissions, will be able to carry 100 TEU and will have a range of 100 nautical miles. In terms of digitalisation, one of the core technical issues for the realization of unmanned shipping is navigation and its processes. For example, Rolls-Royce set up a prototype of a 360-degree virtual reality bridge which will enable crewless ships to be commanded from the shore; connected sensors such as radar, lasers and computer programmes will allow the unmanned vessels to pilot themselves with the shore-based captain or vessel controller taking over in cases where there is a problem or for complex docking procedures.

Legal aspects for the operational use of unmanned vessels

From an international legal perspective there are certain core issues that are likely to arise concerning the use of unmanned merchant ships. The most urgent question is whether unmanned merchant vessels are regulated by the international law of the sea.

Applicability of the international law of the sea

The prevailing question is whether the international law of the sea, especially the UNCLOS, is applicable to unmanned merchant vessels. This requires a three-step analysis: Firstly, what kind of legal status unmanned merchant vessels are entitled to under international law, e.g. whether they are ships within the meaning of the international law of the sea. This is to be followed by the assessment of the necessary connection between the ship or vessel and the flag State. Finally, the third point constitutes the question of whether unmanned merchant vessels are capable of being regulated by existing international law concerning the conduct of ships and vessels.

Determination of a “merchant ship”

Apart from the current state of the art of merchant shipping, however, the term “merchant ship” means, in general, a vessel used for the transportation of goods and/or passengers and distinct from other ships for example warships under the 1982 United Nations Convention on the Law of the Sea (UNCLOS) and State ships operating for commercial and non-commercial purposes under the UNCLOS (such as police and customs ships). Since unmanned merchant vessels are still not addressed by common definitions of international laws of the sea and to encompass the crewless-element of unmanned merchant ships, an approach to define unmanned vessels is as follows:

“An autonomous vehicle that can operate safely and effectively in a real world environment while doing operations of direct commercial value and which can be manufactured, deployed, operated and retrieved at an acceptable cost. The corresponding definition of autonomy is an automated system that has the capability of making independent sensor based decisions beyond ordinary closed loop control.”

The legal status of unmanned merchant vessels

The definition of a ship is not entirely clear within the regulations of the international laws of the sea; there exists a great variety of concepts to define the term “ship” (c.f. UNCLOS; COLREGs; London Dumping Convention; OSPAR-Convention, ILO-Conventions, UN Registration Convention). The conventions referred to above focus on a ship as a means of transport, a modest man-made structure, being engaged in maritime navigation or featuring a certain size. If one takes the lowest common denominator of the above mentioned definitions, the following definition of a ship results:

“A ship is a human-made craft, including submersible vessels, destined for or able to transport goods or people.”

With regard to unmanned merchant vessels, however, all the criteria of the definition are fulfilled. An unmanned merchant vessel constitutes a man-made structure and its object is to carry goods or people from one port to another. Apart from the prerequisites of this definition, an unmanned merchant vessel also meets the additional criteria set by the ocean treaty-definitions. For example, an unmanned merchant vessel furthermore navigates through open waters and because its intended purpose is to be engaged in the cargo shipping sector, it can be expected that the size of unmanned merchant vessels, compared with the ReVolt concept, will soon exhibit more than 500 registered tons as the suggested threshold set by the 1986 UN Registration-Convention.

In respect of the crewlessness of an unmanned merchant vessel, it is remarkable that none of the scrutinized ocean treaties presupposes that a ship must be manned. As a result, crewlessness is not a decisive element in constituting a ship.

Capability of being regulated by international law of the sea

At the international level ships and vessels are under the diplomatic protection of the flag State due to their nationality. Pursuant to the International Tribunal for the Law of the Sea (ITLOS) this requirement will be satisfied by the fact of bare registration alone, and need not be accompanied by more substantive links between the vessel and the flag State. The problem, however, is that many of the existing international regulations assume that there is a crew on board and that many rules deal with which work processes and which routines are required by this crew to ensure a safe voyage. Taking into account the wide definition of vessel in the meaning of the COLREGs, encompassing unmanned merchant vessels, this allows for a first proposition that the COLREGs are open for regulating unmanned merchant vessels, even though no specific reference exists regarding regulations in relation to unmanned vessels. Further, none of the COLREG-rules presuppose personnel on board of a ship with the effect, there would be no need to amend the COLREG-rules regarding unmanned vessels.

With regard to the SOLAS and other international conventions relating to the conduct of vessels, the same tenets apply as they do to the SCTW and the COLREGs: The treaties do not pose a legal obstacle against the operation of unmanned vessels on the international plane.

Finally, the unmanned merchant vessel’s eligibility to benefit from the navigational freedoms enshrined in the UNCLOS needs to be addressed as well. The freedoms of the high seas according to article 87 UNCLOS are freedoms granted to the States. The provision entails no indication that States have, in order to exercise these freedoms, to employ certain means or special crafts. However, even if this would be the case, since unmanned merchant vessels are ships or vessels within the definite meaning of the UNCLOS, there is no reason for denying States the exercise of the freedoms by unmanned merchant vessels.

Hence, as a result, unmanned merchant vessels may lawfully exercise the freedoms of the UNCLOS on the high seas. This entitlement applies as well in respect of the exclusive economic zone under the territorial sea and internal waters of another State as well as in the archipelagic waters.


There are some considerable real-life challenges unmanned merchant vessels will have to face. Unmanned vessels do not only have to operate in open sea mode without malfunctions, detect small objects, collision detection and deviation, but also to release the vessel from/to autonomous operation during troubleshooting in a manoeuvring mode with malfunctions, and have to cope with scenarios like piracy, boarding and ship retrieval or a rope in the propeller. However, the current legal framework – which de lege ferenda will develop further to encompass specific questions relating to the operation of unmanned vessels – is capable of supporting the operation of unmanned ships on the merits

For a more detailed analysis of the aforementioned legal framework on the operation of unmanned merchant vessels under the international law of the sea c.f. Daum, Stellpflug “The implications of international law on unmanned merchant vessels” – Journal of International Maritime Law 2017, 363 – 374).