Reliable anti-collision control algorithms conforming with the rules regulating traffic at sea, the International Regulations for Preventing Collisions at Sea (COLREG), are essential for the deployment of autonomous vessels in waters shared with other ships. The development of such methods is an active field of research. However, little attention has been given to how these rules are interpreted by experienced mariners, and how such information can be parametrised for use in automatic control systems and autonomous ships. This paper presents a method for exploiting historical automatic identification system (AIS) data to characterise parameters indicating the prevalent practices at sea in encounters with high collision risk. The method has been tested on data gathered in areas off the Norwegian coast over several years. Statistics on relevant parameters from the resulting dataset and the relation between them is presented. The results indicate that the strongest influence on vessel behaviour is the type of situation, and the amount of land and grounding hazards in the vessel's proximity.

With the rapid development of the maritime industry and the emergence of unmanned ships, it is necessary to continuously review the International Regulations for Preventing Collisions at Sea (1972, COLREGs). This paper provides an overview of the developing history of the COLREGs and summarises the interpretations made by the International Maritime Organization official and academic scholars. Additionally, the paper discusses the application of the COLREGs in collision avoidance geometry and autonomous collision avoidance systems. Furthermore, the necessity and key points of revisions to adapt to industry advancements are discussed, along with an analysis of the main challenges faced. Finally, in light of the continuous progress and implementation of the outcome of the Regulatory Scoping Exercise for the Use of Maritime Autonomous Surface Ships (MASS), the paper points out that achieving consistency between manned and unmanned vessels, as well as developing COLREGs-based autonomous collision avoidance systems for more complex scenarios, is expected to be a significant trend in the future.

Maritime navigation is a complex task involving the acquisition, analysis, and interpretation of information using seamanship, professional knowledge, and technology. As the maritime industry transitions towards maritime autonomous surface ships (MASS), there is an increasing gap between the operator and the technology. This paper explores a collision avoidance decision support system for navigation from the navigator's perspective. The system, developed by Wärtsilä, is called Advanced Intelligent Manoeuvring (AIM) and can generate suggestions for course or speed alterations based on data from surrounding traffic. Nineteen Swedish navigators completed three ship traffic scenarios with and without decision support. Qualitative data were collected using interviews and analysed with thematic analysis. The results show that the participants perceive the decision support system as an advisory tool to visualise how traffic situations could unfold, a task currently difficult for most navigators. This paper discusses the present and near future of maritime navigation, highlighting the benefits of automation, while remaining vigilant about the potential dangers.

Demonstrations and local tests of several maritime autonomous surface ships (MASS) have recently been carried out. From a technological standpoint, MASS are becoming able to handle actual operations in certain sea areas. Since 2017, the MSC (Maritime Safety Committee) of the IMO (International Maritime Organization) has been discussing legal problems with the Regulations for Preventing Collisions at Sea (COLREGs) with regard to MASS operation. The purpose of this paper is to clarify the rules from the perspective of seafarers, who need to interpret COLREGs when dealing with MASS in ship handling situations on the sea, and also to discuss possible required amendments to COLREGs. This paper attempts to clarify the extent of current interpretations while also taking into account the answers to questionnaires received from 130 pilots, ship captains and navigation officers concerning COLREGs for MASS operation. Given the four common principles of COLREGs, it is considered whether the principles need to be changed with the introduction of MASS from the viewpoint of seafarers.

Economic and technological development has increased the amount, density and complexity of maritime traffic, which has resulted in new challenges. One challenge is conforming to the distinct evasion manoeuvres required by vessels entering into near-collision situations (NCSs). Existing rules are vague and do not precisely dictate which, when and how collision avoidance manoeuvres (CAMs) should be executed. The automatic identification system (AIS) is widely used for vessel monitoring and traffic control. This paper presents an efficient, scalable method for processing large-scale raw AIS data using the closest point of approach (CPA) framework. NCSs are identified to create a database of historical traffic data. Important features describing CAMs are defined, estimated and analysed. Applications on a high-quality real-world data set show promising results for a subset of the identified situations. Future applications may play a significant role in the maritime regulatory framework, navigation protocol compliance evaluation, risk assessment, automatic collision avoidance, and algorithm design and testing for autonomous vessels.

Non-compliance with or misinterpretation of the International Regulations for Preventing Collisions at Sea (COLREGs) when assessing vessel encounters, and the lack of good communication between the vessels involved in a critical situation, are primary contributing factors in collisions. Vessels engaged in an encounter should be aware that they are part of the same scenario and situation, which can become critical. Sharing and contrasting their information about the encounter would help those responsible to take manoeuvring decisions in a consistent way. There are situations whose evaluation by the respective officers in charge of the navigational watch may diverge and lead to disagreements on the actions to be taken. If there is no proper inter-ship communication, a collision may result. This paper presents a proposal for safety communication implemented in a programmable system using common equipment (automatic identification system), and applies it to a case study of one such special situation, showing how it could help to reduce the risk of collision.

Autonomous ships are gaining in importance and are expected to shape the future of the global shipping industry. This evolutionary shift raises serious issues about compliance with the International Regulations for Preventing Collisions at Sea 1972 (COLREGs). This paper reviews the literature on autonomous ships from the perspective of the obligations of good seamanship imposed by COLREGs. The authors conclude that to facilitate the introduction of autonomous ships, the application barriers presented by COLREGs need to be analysed. With this goal, this paper presents a perspective from navigational practice. Four nautical scientists and two deck officers were invited to give their opinions. The analysis indicates that COLREGs require further elaboration and amendments to eliminate uncertainty of interpretation. In particular, the paper highlights the need to amend the ‘look-out’ rule (COLREGs Rule 5) to permit look-out by ‘computer vision’ alone while, at the same time, preserving the distinction between vessels navigating in restricted visibility and in sight of one another.

E-navigation poses significant challenges for shipping. The analysis of the legal norms in the International Regulations for Preventing Collisions at Sea (COLREGS) and court decisions supports the use of information technology on the bridge for the purpose of improving navigational safety. However, the current regulatory and standardisation requirements hamper the introduction of new information streams in navigational systems and remove the incentives for investment in navigation technology. The liability arising from navigational failures will remain on the employer of the crew irrespective of how the additional navigational information is provided to the navigational systems. The shipowner's liability may depend on the way information streams are provided to the ship only within the context of the Civil Liability Convention (CLC) 1992 and other similar pollution conventions where the characterisation of the navigational system as a navigational aid or an aid to navigation may decide the issue of liability. Research on the legal background of these terms underlines the need for a clear distinction between the two terms to be made. An interpretation is proposed which ensures that the CLC liability exception operates in accordance with the underlying legal requirements.

This paper presents a real-time and deterministic path planning method for autonomous ships or Unmanned Surface Vehicles (USV) in complex and dynamic navigation environments. A modified Artificial Potential Field (APF), which contains a new modified repulsion potential field function and the corresponding virtual forces, is developed to address the issue of Collision Avoidance (CA) with dynamic targets and static obstacles, including emergency situations. Appropriate functional and safety requirements are added in the corresponding virtual forces to ensure International Regulations for Preventing Collisions at Sea (COLREGS)-constrained behaviour for the own ship's CA actions. Simulations show that the method is fast, effective and deterministic for path planning in complex situations with multiple moving target ships and stationary obstacles and can account for the unpredictable strategies of other ships. The authors believe that automatic navigation systems operated without human interaction could benefit from the development of path planning algorithms.

Maritime accident statistics reveal that ship collisions are among the most frequent and severe accidents. The same statistics indicate that most of them are caused by human error, mainly due to breaches of the International Regulations for Preventing Collisions at Sea (COLREGs) and to the lack of communication between ships. There are also special situations where there is some ambiguity in the application of the COLREGs. In such occasions, and if there is no communication between the ships involved, compliance with the Rules may still end up in a collision. This article brings a new approach to Collision Avoidance Systems (CAS) and presents the earliest stages in the development of safety functions for the reduction of ship-to-ship collision risk on the high seas. These functions will help the concerned ships achieve coordinated compliance with the COLREGs. Functional safety standards are applied and, in their implementation, real, accessible electronic programmable systems (hardware and software) will be used.

When a collision occurs between two ships on the high seas, very likely one may need to determine who should be liable for the collision and the apportionment of liability between them. However, it is not unusual to see a collision between an anchored vessel and another vessel underway. When determining apportionment of liability between them, it seems that there is a presumption of fault against the vessel underway. To counteract such a presumption, the author discusses some issues in respect of collisions between a vessel at anchor and others underway under the International Regulations for Preventing Collisions at Sea, 1972 (COLREGs) by examining the obligations of anchored vessels to avoid a collision at sea.

Vessels are found frequently operating under the Automatic Identification System (AIS) ‘Not Under Command’ (NUC) option near ports and close to shores in order to report their manoeuvre status to nearby traffic. When asked if they are under any kind of restriction regarding their engines or steering, they often answer that they are just drifting or waiting for the pilot or shipowner's orders. The question that arises is this: “Are these vessels really under an NUC situation or can the AIS Navigational Status menu adapt to the different circumstances of navigation?”.

In the middle years of the 20th Century, few merchant ships were fitted with radar and, on those that were, shipmasters often looked upon it as a distraction from a watchkeeper's proper duties rather than as a useful aid to navigation.

For shipmasters of that persuasion, the only place to keep watch was outside the wheelhouse on an exposed bridge wing; mostly the starboard wing because the COLREGS (‘Collision Regulations’ or, more properly, ‘The International Regulations for Preventing Collisions at Sea’) required us to give way to ships approaching from the starboard side. Well, the bridge wing was an attractive place to spend a few hours on a calm, tropical night, but it could be highly disagreeable and sometimes, I thought, actually dangerous, in a North Atlantic rainstorm.

The January 2009 issue of the Journal of Navigation included a paper (John Wilde Crosbie 2009) entitled, “Revisiting the lessons of the early steering and sailing rules for an e-navigation age.” Following a description of the development of the COLREGS from the early 19th century, he concluded that the current steering and sailing rules should be replaced by a single rule more suited to modern conditions. This might take the form of a rule stating that a vessel taking action to avoid collision should not pass ahead of the other vessel. Such a rule would require a radical change in the philosophy of collision avoidance at sea, and evidence is required that it would be both effective and acceptable by mariners. Radar simulator experiments, conducted by the author some years ago in another context, suggest that this might be the case. An analysis of the experimental results and some conclusions are reported in this paper. The author recommends that further trials, specifically designed to test the Crosbie proposals, would be desirable.

There is currently considerable interest in the international regulations for preventing collisions at sea (the COLREGS). Suggestions for changes are made, but their validity is difficult to assess because there is little possibility of testing new proposals before they are introduced. There is, however, the possibility of considering the history of the COLREGS, and their effectiveness, as they have evolved over the years. In this paper, the author's aim is to look at the lessons that may be learned from one, particularly tragic, collision between the Princess Alice and the Bywell Castle in 1878. Opinions differ as to whether a study of history is likely to be a useful exercise.

This study provides both a spherical understanding about autonomous ship navigation for collision avoidance (CA) and a theoretical background of the reviewed work. Additionally, the human cognitive abilities and the collision avoidance regulations (COLREGs) for ship navigation are examined together with water based collision avoidance algorithms. The requirements for autonomous ship navigation are addressed in conjunction with the factors influencing ship collision avoidance. Humans are able to appreciate these factors and also perform ship navigation at a satisfactory level, but their critical decisions are highly subjective and can lead to error and potentially, to ship collision. The research for autonomous ship navigation may be grouped into the classical and soft computing based categories. Classical techniques are based on mathematical models and algorithms while soft-computing techniques are based on Artificial Intelligence (AI). The areas of AI for autonomous ship collision avoidance are examined in this paper are evolutionary algorithms, fuzzy logic, expert systems, and neural networks (NN), as well as a combination of them (hybrid system).

In order to avoid a collision it has clearly been proved that for most seafarers there exists a set of possible situations known as head-on, crossing and overtaking, while ignoring in a general way the behaviour they should carry out when their vessel is in conditions of restricted visibility. It is obvious that the existence of two different manoeuvre methods in relation to the prevailing visibility confuses the navigator. But there is still more. With the arrival of AIS, the present wording of paragraph d) of Rule 19 leaves the seafarer in a state of total uncertainty when deciding the appropriate manoeuvre, so its amendment must be dealt with as a maximum priority. The following paper tries to find a solution to the dilemma, even though this does not imply a radical change in the general conception that a mariner may have of collision avoidance.

Re-visiting the requirement to introduce amended collision regulations to meet the developing threat in encounters between high-speed craft and slower, mainly smaller vessels. This paper looks at the requirements of different types of encounter and the ability to identify high-speed craft through AIS. It introduces proposed changes to the Colregs that could help to reduce the perceived threat to small, slow craft.

Although AIS is already in use in a range of vessels, there has been little public discussion on how AIS should interact with the COLREGS in practice. The objective of this paper is to make a contribution to that debate, while recognising that “best practice” will evolve as more practical experience is obtained. The paper suggests the approach that should be adopted in several areas, but concludes that, overall, AIS is nothing more than one of several tools that should enable mariners to fulfil their existing obligations under the COLREGS.