1.11 Conduct in Restricted Visibility (Rule 19)

Rule 19 — Different Regime, Not Foggy Rule 15

Rule 19 governs conduct of vessels in restricted visibility. It applies to vessels not in sight of one another when navigating in or near an area of restricted visibility (fog, mist, falling snow, heavy rain, sandstorms, or similar causes). The single most expensive Master 100 mistake in this section is importing Section II logic — "I am stand-on in a crossing" — when you only have a radar paint or a fog signal. If you cannot observe the other vessel visually, you are not in Rules 12–18 geometry. You are in Rule 19.

Q100 scores Rules at 90%. A fog stem that offers "stand on because the target is on your port bow" is almost always a trap.

19(b)–(c) — Safe Speed and Section I Still Apply

Every vessel shall proceed at a safe speed adapted to the prevailing circumstances and conditions of restricted visibility. A power-driven vessel shall have her engines ready for immediate manoeuvre.

Safe speed (Rule 6) is always required; Rule 19 tightens the adaptation to fog. For a Master of a passenger vessel, that usually means slower than clear-weather cruise, engines immediately available (not on long warm-up delays), lookouts posted (Rule 5), and navigation lights on as required in restricted visibility (Rule 20). Rule 19(c) also requires due regard to restricted-visibility conditions when complying with Section I of Part B (Rules 4–10: lookout, safe speed, risk, action to avoid collision, narrow channels, TSS).

19(d) — Radar Alone: Detect, Decide, Avoid (With Course Bans)

A vessel which detects by radar alone the presence of another vessel shall determine if a close-quarters situation is developing and/or risk of collision exists. If so, she shall take avoiding action in ample time, provided that when such action consists of an alteration of course, so far as possible the following shall be avoided:

1. An alteration of course to port for a vessel forward of the beam, other than for a vessel being overtaken.
2. An alteration of course toward a vessel abeam or abaft the beam.

These are among the highest-yield Rule 19 facts on Master exams.

Why the Port Ban Forward of the Beam?

In fog, both vessels may detect each other only by radar and both may choose a turn. If each turns port for a target forward of the beam, tracks can converge. Prefer starboard alterations when a forward target requires a course change (unless the geometry is a true overtaking situation where different logic applies). The rule's "so far as possible" language means this is the default avoidance discipline, not an invitation to invent creative port turns.

Why Not Turn Toward Abeam/Abaft Targets?

Turning toward a vessel already abeam or abaft shortens CPA and can create a crossing from what might have been a pass. Prefer action that opens the situation — often a turn away, a speed reduction, or both — rather than helm into the radar paint.

Overtaking Exception

The port-ban for vessels forward of the beam excepts a vessel being overtaken. If you are overtaking and must alter, the general forward-of-beam port prohibition is relaxed for that overtaking geometry — but you still must keep clear and act early. Do not use the exception as a free pass to drive into close quarters.

19(e) — Fog Signal Forward of the Beam / Unavoidable Close-Quarters

Except where it has been determined that a risk of collision does not exist, every vessel which:

• hears apparently forward of her beam the fog signal of another vessel, or
• cannot avoid a close-quarters situation with another vessel forward of her beam,

shall reduce her speed to the minimum at which she can be kept on her course. She shall if necessary take all her way off and in any event navigate with extreme caution until danger of collision is over.

This is the classic "hear one prolonged blast ahead in fog" drill:

1. You have not determined that risk is absent.
2. Signal is apparently forward of the beam.
3. Slow to minimum steerage way — or stop (take all way off) if needed.
4. Navigate with extreme caution until the danger is over.

Do not race into the sound at cruise speed hoping the other vessel is "probably far away." On a passenger deck in fog, Rule 19(e) is both exam law and operational survival.

Rule 19 Action Table

Master Scenario: Passenger Vessel Entering a Fog Bank

You command a 75-foot near-coastal passenger vessel approaching a harbor in thickening fog. Visibility drops below useful visual range. Correct Rule 19 package: reduce to a visibility-adapted safe speed, confirm engines ready for immediate maneuver, post lookouts, show navigation lights, use radar to plot whether any target is developing close-quarters or risk, and if a strong radar target sits forward of the beam with decreasing CPA, take early avoiding action — prefer a starboard course change or speed reduction rather than a port turn into the target. If you hear a fog signal apparently ahead and cannot ascertain that risk is absent, drop to minimum steerage way or take all way off and creep with extreme caution. Incorrect: claim stand-on because the radar target is on the port bow, hold harbor-approach cruise speed, or turn port toward the paint "to get out of the way quickly."

Connecting Rule 19 to Rules 5–8

Rule 19 does not cancel lookout, risk assessment, or action quality:

• Rule 5 lookout by all available means — eyes, ears, radar, AIS as appropriate — is more important, not less, in fog.
• Rule 7 risk detection still uses compass bearings when visual, and radar plotting / systematic observation when not.
• Rule 8 still demands positive, early, readily apparent action and permits slackening speed or taking all way off.

What Rule 19 removes is the comfort of "I am stand-on; she must keep clear" when you are not in sight of one another.

Exam Framing for Q100 (90%)

Memorize five Rule 19 anchors: not in sight / in or near restricted visibility; safe speed adapted to visibility + engines ready; radar alone → determine close-quarters/risk → act in ample time; no port for vessel forward of beam (except overtaking); no turn toward vessel abeam/abaft; fog signal forward of beam → minimum speed or all way off + extreme caution. Master passenger scenarios simply raise the cost of getting any of those wrong.