Question 19 ONC01 - Master/Chief Mate Unlimited Tonnage

The Correct Answer is A. **Explanation of Option A (Correct):** Option A describes a vessel that is on your starboard quarter (coming up from behind/alongside you) with the following characteristics: * **Range decreasing:** The distance between the vessels is getting smaller. * **Bearing is constant:** The relative direction (angle) of the other vessel from your own vessel is not changing. According to Rule 7 (Risk of Collision) of the COLREGs (International Regulations for Preventing Collisions at Sea), if the compass bearing of an approaching vessel does not appreciably change, **risk of collision shall be deemed to exist.** This is the classic definition of a Constant Bearing, Decreasing Range (CBDR) situation, which demands immediate action to avoid collision, regardless of whether the vessels are in international or inland waters. **Explanation of Incorrect Options:** **B) A vessel is 22 degrees abaft your port beam, range increasing, bearing is constant.** * While the bearing is constant, the **range is increasing**. If range is increasing, the vessels are moving apart. Risk of collision does not exist, though the situation still needs monitoring. **C) A vessel is broad on your starboard beam, range decreasing, bearing changing rapidly to the right.** * The range is decreasing (getting closer), but the **bearing is changing rapidly**. A rapid change in bearing means the vessels are on passing courses and will likely cross ahead or astern of each other, usually indicating that collision risk does not exist (though caution is still needed, especially if the passing distance is small). **D) A vessel is 22 degrees on your port bow, range increasing, bearing changing slightly to the right.** * The **range is increasing** (moving apart), and the **bearing is changing**. Both factors indicate that the vessel is moving to pass clear and that risk of collision does not exist.