Official rule text as published in the U.S. Coast Guard Navigation Rules
Rules 11 – 18 apply to vessels in sight of one another.
MyCOLREGS explanation
Summary
Rules 11 through 18 - the ones covering sailing vessels, overtaking, head-on and crossing situations, and give-way/stand-on duties - only kick in once you can actually see the other vessel. If you can't see her, because of fog, darkness, or distance, you're not in a Rule 11-18 situation with her; Rule 19's restricted-visibility approach takes over instead.
Real World Example
The in-sight line exists because Rules 13 through 17 depend on judgments only your eyes can make reliably, like reading another vessel's aspect or heading - a radar target gives you a blip's course and speed, but not the sidelight or masthead-light picture those rules were built around.
Practice Questions
Q1. Rule 11 sets a condition for a whole family of duties about which vessel is the give-way vessel and which is the stand-on vessel - head-on, crossing, sailing vessel vs. power-driven vessel, and so on. According to this rule's own text, when do those duties actually start applying between two vessels?
A. Only during daylight hours.
B. Whenever their AIS targets overlap on a chartplotter.
C. Whenever vessels are within one nautical mile, regardless of visibility.
D. Only when the vessels are in sight of one another.
Q2. As with Question 1, Rule 11 is about when the rules about give-way/stand-on apply. You detect another vessel only by radar in dense fog, with no visual contact. Which family of rules governs the encounter?
A. The crossing/overtaking give-way/stand-on duties described above, since risk of collision exists.
B. The separate restricted-visibility rules instead, since those give-way/stand-on duties only apply when vessels are in sight of one another.
C. The narrow-channel rules.
D. No rule applies until visual contact is made.
Practice Question Answers
Q1.
D. Only when the vessels are in sight of one another. Rule 11 states that these give-way/stand-on duties apply to vessels in sight of one another - visibility of the other vessel, not distance or electronics, is the trigger. A substitutes a time-of-day trigger for the actual test. B and C substitute a technical or distance-based trigger - AIS overlap, a distance threshold - for what Rule 11 actually requires: whether the vessels are in sight of one another.
Q2.
B. The separate restricted-visibility rules instead, since those give-way/stand-on duties only apply when vessels are in sight of one another. Rule 11 limits the give-way/stand-on duties to vessels in sight of one another - a radar-only contact in fog falls instead under the separate restricted-visibility rules. A applies the in-sight duties to a situation where the vessels aren't in sight - the very condition Rule 11 requires. C reaches for an unrelated set of rules. D wrongly assumes no rule governs the encounter until visual contact, when the restricted-visibility rules govern it right now.