# A Novel Method for Risk Assessment and Simulation of Collision Avoidance for Vessels based on AIS
## 6 Conclusions and Further Work  
In the method using the DCPA and TCPA to calculate the collision capability, it is clear that when two ships are in the same lane, the DCPA is always zero, which means that collision will be immediate, no matter how far away the two ships are. Furthermore, when the ship moves in the same lane and moves slower than the target ship, the possibility of collision is not present, which is not accurate. A comparison of Cases 3 and 4 in Table 1 serves as an illustrative example of the superiority of the method used in this article. Case 4 seems more dangerous than Case 3, because the distance to the point of collision was 0.8716 nautical miles closer than 7.2505 nautical miles. However, in Case 3, the distance between the two ships was actually smaller than that in case 4: 8 nautical miles smaller than 10 nautical miles, and the speeds were faster: 15 kn and 13 kn. Along with the influence of the different course and azimuth, the time approach to the point of collision of Case 3 was 0.2254 hour when the time approach to the point of collision of Case 4 was 0.7663 hour. Additionally, in the combination of factors to calculate the CRI, that Case 3 was more dangerous than Case 4 was accurate. The CRI indicates the collision risk of the two ships; the higher the value of the TCPA, the closer the distance between the two ships, and the greater the speed of the ship and the angle of the ship. This index is especially useful with a high density of boats in cruising areas, when the distance between the ships is not too far, and the weather conditions are not favorable. Dynamic visualization results showed that the collision risk assessment model can be applied in practice. Avoiding operations are widely applied by the operational officer, who observes the target ships for 3 to 6 minutes, then determines the parameters of the target ship, and explains the collision risk. This model can be integrated into the AIS to help the sailor to quickly and accurately assess the collision risk, thereby applying the COLREGS-72 collision avoidance principle to handle the situation. A small-size embedded system with the collision risk assessment model can be installed on-board for navigation, and equipped on small vessels and fishing vessels to avoid collision without an ARPA system. This collision risk assessment model can also be used at the base station, VTS centers, and NoC, to monitor, manage, and issue hazard warnings for vessels in the operating area of stations. The limitations of this paper are the effects of ship size, ship type, weather condition, and the dynamic activity of the target ship on safety, which were not been researched here, as they were beyond the scope of this study. The calculation collision capability is based on information from the AIS system. Therefore, the speed and course used in the article were the SOG and COG, and not the actual speed of the ship through the water surface. This will be affected in complex weather conditions and high-flow sea currents, especially in the case of head-on situations. The number of DLA is one of the parameters involved that was set at one nautical mile to calculate the CRI. In future study, when the ship target is in a danger zone, for the number of DLA required to calculate the details to fit the type of ship, we will use the ship's domain to calculate the CRI in more detail. The application of the proposed method is necessary to enhance the capability of risk assessment by collecting more encountered conditions in practice. Furthermore, the authors will continue with this research and develop a hardware device to improve the AIS system. [PERSON] provided the idea of the algorithms, carried out the simulations, and drafted the manuscript. [PERSON] supervised the work, arranged the architecture, and contributed to the writing of the manuscript. [PERSON] supervised the work and provided the major direction of the research. This research was funded by the National Natural Science Foundation of China, No. 61231006.