1.11 Conduct in Restricted Visibility (Rule 19)

Rule 19: Conduct of Vessels in Restricted Visibility

Rules 11 through 18 — the whole "in sight of one another" toolkit of stand-on and give-way — switch off the moment you can no longer see the other vessel. Rule 19 governs vessels navigating in or near an area of restricted visibility that are not in sight of one another. Fog, heavy rain, snow, and smoke all trigger it. Because you cannot see the other vessel, there is no stand-on vessel here: both vessels have obligations, and neither has the "right of way." This is the single most important idea in the rule.

Safe speed is mandatory

Rule 19(b) requires every power-driven vessel to have her engines ready for immediate maneuver and to proceed at a safe speed adapted to the prevailing circumstances (echoing Rule 6). In dense fog, safe speed may be dead slow or even stopped. The classic test question: a vessel proceeding too fast to stop within the distance she can see is by definition not going at a safe speed.

The two-part response to a fog signal

Rule 19(e) covers what to do when you hear another vessel's fog signal apparently forward of your beam, or cannot avoid a close-quarters situation with a vessel forward of the beam. Unless you have determined that risk of collision does not exist, you must:

1. Reduce speed to the minimum at which you can be kept on course, and
2. if necessary, take all way off — stop the vessel — and in any event navigate with extreme caution until the danger of collision is over.

The two forbidden turns

Rule 19(d) is where candidates lose points. When a vessel detects by radar alone the presence of another vessel and a close-quarters situation is developing or a risk of collision exists, she must take avoiding action in ample time. If that action is a course change, then so far as possible she must avoid the following two maneuvers:

A memory hook: "Don't turn port for a vessel forward; don't turn toward one abeam or behind." The logic behind the first rule is that if both vessels were on reciprocal-ish courses and both turned to port, they would turn into each other — the rules push everyone toward starboard turns, consistent with the head-on rule you already know.

Radar contact vs. hearing a signal

Notice the rule distinguishes two triggers, and they lead to two different responses:

• Detected by radar alone (you have not yet heard her) → Rule 19(d): avoid the two forbidden turns, act in ample time.
• Heard a fog signal forward of the beam (or unavoidable close quarters) → Rule 19(e): slow to steerageway, stop if necessary.

An exam item may describe a target seen only on radar closing on your starboard bow and ask what alteration is acceptable. Because the target is forward of the beam, a turn to starboard (away from it, to pass astern) is permitted, while a turn to port is prohibited.

Worked example

You are running a power-driven six-pack in patchy fog at 12 knots. You hear a single prolonged blast that seems to come from fine on your port bow, and you have no radar contact and no visual. Apply Rule 19(e): you cannot yet rule out risk of collision, so reduce to bare steerageway and be prepared to stop. You do not get to "hold course as the stand-on vessel," because in restricted visibility there is no stand-on vessel. Navigate with extreme caution and keep listening for the next signal to sense whether the bearing is opening or closing.

Now change the facts: a radar target appears fine on your starboard bow at three miles, closing. Under Rule 19(d) you take early action; a bold alteration to starboard to open the range and pass well clear is proper. Turning to port would be exactly the forbidden move for a contact forward of the beam.

Fog signals belong here too

Rule 19 works hand-in-hand with Rule 35 (sound signals in restricted visibility), covered in Section 1.17. The moment visibility drops you must both slow down (Rule 19) and begin sounding the correct fog signal (Rule 35). Many candidates memorize the signals but forget that the conduct rule — safe speed, engines ready, the forbidden turns, slow-to-steerageway on hearing a signal — is a separate and equally testable body of material.

Key distinctions to lock in

• In sight of one another → Rules 11–18 apply, there is a stand-on and a give-way vessel.
• Not in sight, in/near restricted visibility → Rule 19 applies, no stand-on vessel, both act.
• The two forbidden alterations (no port turn for a contact forward of the beam; no turn toward a contact abeam/abaft) apply to action taken to avoid a radar-detected vessel.
• On hearing a fog signal forward of the beam you cannot avoid, slow to steerageway and be ready to stop.