# The Ocean-Going Autonomous Ship--Challenges and Threats
## 2 Navigational Equipment and Related Challenges
### Collision Avoidance--Issues on Manned Vessels Versus Challenges to the Unmanned Platforms  
Collision avoidance is a critical task for all vessels, including autonomous ships. The Convention on the International Regulations for Preventing Collisions at Sea (COLREGs) entered into force in 1977. The set of rules is based on a good seamanship and has been established through decades of marine operations. Although those operations have been performed by manned vessels and COLREGs put all the required tasks and the responsibility on vessels' crew officers of the watch and masters of sea-going ships. Development of rules of cooperation between manned and unmanned vessels is one of the biggest challenges of autonomous ships industry. While COLREGs requires the decisions to be taken by humans, the studies from marine accidents reports prove that 60% of accidents are caused by human error. Structure or mechanical failure has been a direct reason for an accident in 19% of cases and only 10% has been caused by equipment failure [28]. Other sources claimed that even 80% to 85% of all accidents are caused by directly initiated human error or a lack of a proper response to the situation [29]. [PERSON] in [29] listed the common reasons of collisions at sea, which refers to human actions on board. They are listed below in the order of the number of occurrence in the collision reports analyzed by the authors of [29]:  
1. Bad decision making
2. Poor lookout
3. Poor manning level
4. Poor use of radar
5. Broke rules
6. Inexperience
7. Poor communication between personnel
8. Fatigue
9. Unfamiliarity with equipment
10. Poor training
11. Over working
12. Radio failure  
When we are trying to find here the reference to the unmanned or autonomous vessels, it is all dependent on the level of control, in other words, on the level of human interference with the unmanned ship operation. Bad decisions, the most common collision reason, can occur in case of remotely controlled vessels to. In case of autonomy, it will be the result of the algorithm or artificial intelligence implemented on the vessel and its reliability will depend on the level of sophistication of the system. The most complex situation is the crossing situation of the manned and autonomous platforms. While the autonomous ship will always behave according to the algorithm (assuming the proper performance of its components), the behavior of the people is often unpredictable and the ignorance of rules occurs. The problem of a proper lookout on the manned vessels is often caused by the reduction in the number of crew on board and overwork. In the case of unmanned ships, this is a more technical challenge. Both remotely controlled vessel and autonomous ship need to sense the environment and send the information to shore in real time or independently make decisions based on that. The reliability and accuracy of sensors onboard or the communication system capabilities will limit the amount of information accessible at the particular moment of time for the operator or the decision-making algorithm. Poor manning level, fatigue and over working--all these factors refer to the working conditions. Working at sea has been always automatically understood as connected with danger, parting with families, loneliness and tiredness. The introduction of unmanned vessels technology immediately moves some of the workstations from sea to shore, reducing the risk of the negative impact of hard-working conditions on the safety of the vessel. Inexperience or poor training are also among the common causes of ships' collisions. The issue of proper education of unmanned vessels operators or autonomous ships supervisors will be a great challenge in the close future. There is certainly a high need of real at-sea experience to properly assess the situation of the vessel during the sea passage.