Question 19

The Correct Answer is A. A risk of collision is deemed to exist if the bearing of an approaching vessel does not appreciably change (Rule 7(d)(i) of the COLREGs). Range decreasing combined with a constant (or nearly constant) bearing is the definition of a collision course. **Why option A ("A vessel is on your starboard quarter, range decreasing, bearing is constant.") is correct:** * **Range decreasing:** The vessel is getting closer. * **Bearing is constant:** The angle to the vessel is not changing. * When a vessel is getting closer (range decreasing) and its relative bearing remains unchanged, it means the vessels are converging on the same point simultaneously. This is the definitive indication that a risk of collision exists, regardless of the relative position (though in this specific case, the position on the quarter is somewhat unusual for the stand-on vessel, but the rule applies to the existence of risk, not the responsibility). **Why the other options are incorrect:** * **B) A vessel is 22 degrees abaft your port beam, range increasing, bearing is constant.** * **Range increasing:** The vessel is moving away. A collision cannot occur if the range is increasing. * **C) A vessel is broad on your starboard beam, range decreasing, bearing changing rapidly to the right.** * **Bearing changing rapidly:** If the bearing is changing rapidly, the two vessels are not aimed at the same point, and the risk of collision (defined by COLREGs) does not exist. Although the range is decreasing, the change in bearing indicates the vessels will pass clear of each other. * **D) A vessel is 22 degrees on your port bow, range increasing, bearing changing slightly to the right.** * **Range increasing:** The vessel is moving away. * **Bearing changing:** The vessels are not on a collision course. Both factors strongly indicate no risk of collision exists.