To determine if the risk of collision exists, a vessel fitted with radar must use __________.

To determine if the risk of collision exists, a vessel fitted with radar must use multiple methods, including visual observation, radar information, and an understanding of the relationship between vehicles. This comprehensive approach ensures the operator can analyze the situation thoroughly.

Visual observation is crucial because it allows the operator to detect smaller vessels, obstacles, or changes in the environment that radar may not fully capture. Maintaining a steady bearing is essential in understanding the risk of collision; if the vessel's bearing to another vessel remains constant, it indicates that the two vessels are on a collision course.

Using radar alone is insufficient, as it may have limitations such as range, target resolution, or even interference. Therefore, relying solely on any single method could lead to incorrect assessments of collision risk. By using a combination of all available tools and observations—including both radar and visual checks—mariners can make the best decision to navigate safely and avoid collisions.