# A Novel Method for Risk Assessment and Simulation of Collision Avoidance for Vessels based on AIS
## 1 Introduction
Thus, this paper did not integrate the COLREGS rules into the collision avoidance techniques or propose a deterministic path planning algorithm to compute a practical and COLREGS-compliant navigation path. The focus of the process is the procedure for providing a warning to avoid collisions, that chooses the risk model, and that calculates the probability of collision [12; 29]. In practice, small vessels and fishing vessels are not equipped with ARPA systems; collision assessment only uses the DCPA and TCPA parameters on the AIS system. These two parameters have major disadvantages when reflecting ships incorrectly moving into head-on situations and overtaking situations. Thus, this paper referred to a more general approach to calculate the CRI, which comprehends all situations for when a ship moves at sea. As the calculation method used in the article was not too complicated, elements of weather conditions were estimated through the factor of safety that was set at the highest level. The article also emphasized that the human factor was the most important; when the risk of collision becomes high, it will warning the crew to pay attention, and to take action to follow the prevention of COLREGS. Considering the practical requirements for collision avoidance, and based on information including the DCPA, TCPA, distance, and bearing, this paper developed a marine collision risk assessment model and built a simulation program to calculate the collision probability for cruise vessels on the sea, to provide a timely warning and auxiliary for collision avoidance. Next, the level of danger was fundamental to propose corresponding warnings to help sailors to keep attention, and to proceed to collision avoidance, based on the COLREGS-72 rules. This method is useful for small ships and fishing vessels that have limited equipment, and that are not fully equipped with RADAR ARPA, and ECDIS. The ship domain is a well-known concept, defined by [PERSON] (1975) as \"the surrounding waters which a navigator of a ship wants to keep clear of other ships or fixed objects\" [8]. Various mathematical domain models have been proposed, and empirical findings have confirmed the applicability of the concept. This evidence suggests that in similar navigational conditions, domains have similar shapes and sizes. Ships entering the domain of other vessels can be taken to deviate from a reference level, and thus, they present an elevated collision risk. Different domain geometries are found in different areas, but more research is needed to understand the situation-dependence of reference levels in different sea areas and in different weather conditions [8; 30]. The application of a ship's domain in calculating collision is necessary. When the target ship is in the danger zone, it has many calculations to solve. When target ship is not in the danger zone, the collision calculations can be based on the ship's domain to determine the minimum safety distance. The main contribution of this paper is that it provides a calculation of the CRI, where each weight is assigned, according to the danger level that is related to the collision situation by the analytic hierarchy process (AHP) algorithm [11]. AHP is a precise method for selecting decisions, which are believed to be useful for a developer. In the case where quantitative ratings are not available, AHP allows the programmer to still recognize whether one criterion is more important than another. The analytic hierarchy process (AHP) was developed by [PERSON] (1977, 1980, 1988, and 1995), and it is one of the best-known methods. The AHP approach is a subjective methodology where information and the priority weights of elements can be obtained from a system or user, and that designation is based on the assessment and assignment of the developer. It allows the programmer to assess the relative weights of multiple criteria in an intuitive manner. AHP makes the selection process very transparent. In addition, the AHP method provides a unique means of quantifying judgmental consistency.