How to determine risk of collision?

• A. If the bearing to the other vessel does not change and the range decreases, there is a risk of collision.
• B. If the range increases, collision risk is high.
• C. If you hear a horn, collision risk is certain.
• D. If you cannot see the other vessel, there is no risk.

Answer: (A)

The key idea is constant bearing with decreasing range. When the bearing to another vessel stays the same while the distance between you shrinks, you’re on a collision course unless someone alters speed or course. This CBDR pattern is the classic warning sign of an imminent collision, so it’s the strongest indicator among common signals you’d observe.

If the range were getting larger, you’re effectively moving apart, so the collision risk drops. Hearing a horn can indicate someone is signaling or might be maneuvering, but it doesn’t guarantee a collision will occur. And not seeing the other vessel doesn’t mean there’s no risk— there could be a vessel in limited visibility or behind a radar blind spot, so you must maintain lookout and safe navigation practices regardless.