How do you determine risk of collision?

How do you determine risk of collision?

• A. If bearing does not appear to change and the range decreases.
• B. If bearing changes rapidly and the range decreases.
• C. If you are going faster than the other vessel.
• D. If you are in restricted visibility.

Answer: (A)

The key signal for collision risk is the relative motion of the other vessel: if the bearing to that vessel stays essentially fixed while the range to it decreases, you are on a collision course. This happens because both vessels are converging along the same line of sight, so they would occupy the same point at the same time unless you alter course or speed. If the bearing changes—rapidly or otherwise—the line of sight isn’t fixed on a single line toward you, so you’re not following a true collision course even if the distance is shrinking. That means the risk is not as certain, and you should reassess with other information (like your course, speed, and any maneuvers you may need to take). Being faster than the other vessel or being in restricted visibility doesn’t by itself determine collision risk; those factors don’t guarantee a collision course. The reliable indicator remains the bearing remaining constant while the range closes.

The key signal for collision risk is the relative motion of the other vessel: if the bearing to that vessel stays essentially fixed while the range to it decreases, you are on a collision course. This happens because both vessels are converging along the same line of sight, so they would occupy the same point at the same time unless you alter course or speed.

If the bearing changes—rapidly or otherwise—the line of sight isn’t fixed on a single line toward you, so you’re not following a true collision course even if the distance is shrinking. That means the risk is not as certain, and you should reassess with other information (like your course, speed, and any maneuvers you may need to take).

Being faster than the other vessel or being in restricted visibility doesn’t by itself determine collision risk; those factors don’t guarantee a collision course. The reliable indicator remains the bearing remaining constant while the range closes.