Autonomous ships have become a topic of interest for an increasing number of researchers over the last few years. Most of the research that is being performed focuses on autonomous navigation. An important driver for this research is the belief that autonomous navigation will increase safety at sea. In order to evaluate the possible safety benefit of autonomous navigation, it is essential to have an understanding of the risk associated with navigation-related accidents. In this paper, a monetary quantification of the risk associated with navigation-related accidents will be presented, to support designers in determining the acceptable costs of an autonomous navigation system.. It is the intention to provide order-of-magnitude figures for the annual risk for different ship types and sizes. Although it is acknowledged that the analysis comes with uncertainties, the results provide an overview contribution that different damage cases make to the overall risk per year, associated with navigation-related accidents. It is found that the annual risk can be expected to be between €1.5 billion and €2.5 billion, or a €45k to €75k risk per vessel per year. Consequently, the maximum annual safety benefit of autonomous navigation is equal to this figure if autonomous navigation will be able to prevent all navigation-related accidents.

The advent of autonomous ships that are unmanned or low-manned will reduce the number of people at risk at sea. Even when autonomous navigation does not reduce the number of accidents, this means that safety at sea will increase. In fact, increased safety is one of the primary perceived drivers for autonomous shipping, although this safety increase has not yet been quantified in academic literature. In this article a statistical analysis is performed to determine the distribution of human casualties and lost ships over accident types, ship types and ship sizes. Subsequently, based on several scenarios for the implementation of autonomous ships, a quantification of the estimated reduction in loss of life and loss of ships is provided. It is concluded that the implementation of autonomy on small cargo ships with a length below 120 m will have the largest safety benefit, since these ships account for the majority recorded ship losses and lives lost.

In recent years, a significant amount of research has been conducted on autonomous ships. Since it is assumed that these ships will sail with a significantly reduced crew or even without people on board, the design of the ship needs reconsideration. The absence of people on board and the associated safety measures could result in a more efficient design, but amendments in the existing regulatory framework will be needed. In this article, we will focus on potential changes in the Convention for Safety Of Life At Sea (SOLAS) and in particular on the Required Subdivision Index. The index gives a requirement for the allowed probability of sinking when a ship is damaged due to collision. The evaluation is performed by using the principle of equivalent safety, which will ensure that unmanned ships will be at least as safe as manned ships. If the crew is no longer present, the consequences of an incident will be less severe, since the probability of casualties is no longer present. Consequently, a lower subdivision index might be accepted for unmanned autonomous ships. In this article, the damage stability-related level of risk of a manned ship will be derived by means of a risk analysis. Thereafter, the subdivision index for unmanned ships, which ensures an equivalent safety level to similar manned ships, is established for three individual ships. The assessment shows that a reduction in the subdivision index is allowed for unmanned ships and that the reduction will be largest for smaller ships.