Rule 19 — Conduct of Vessels in Restricted Visibility

TL;DR — Rule 19 governs vessels not in sight of one another when navigating in or near restricted visibility. Every vessel must proceed at a safe speed with engines ready; a vessel detecting another by radar alone must act in ample time, avoiding a port alteration for a contact forward of the beam; a vessel hearing a fog signal forward of the beam must immediately reduce to bare steerageway. 33 CFR §83.19

---

What the Rule Says

Scope of Application

Rule 19 applies to vessels not in sight of one another when navigating in or near an area of restricted visibility. 33 CFR §83.19 This is a critical threshold. Rules 11 through 18 — the steering and sailing rules covering give-way, stand-on, crossing, head-on, and overtaking situations — apply only to vessels in sight of one another. 33 CFR §83.11 Once visibility is restricted and vessels cannot be observed visually from one another, those rules yield to Rule 19. 33 CFR §83.03

"In sight of one another" has a precise legal meaning: one vessel can be observed visually from the other. 33 CFR §83.03 Radar contact alone does not constitute being in sight. "Restricted visibility" means any condition in which visibility is restricted by fog, mist, falling snow, heavy rainstorms, sandstorms, or any other similar causes. 33 CFR §83.03 Note the phrase "or near" in Rule 19(a) — a vessel approaching a fog bank is already subject to Rule 19 before she enters it. 33 CFR §83.19

---

Safe Speed and Engine Readiness — Rule 19(b)

Every vessel shall proceed at a safe speed adapted to the prevailing circumstances and conditions of restricted visibility. 33 CFR §83.19 This obligation falls on every vessel without exception — power-driven, sailing, fishing, restricted in ability to maneuver, or otherwise.

There is an additional, specific requirement for power-driven vessels: a power-driven vessel shall have her engines ready for immediate maneuver. 33 CFR §83.19 This is not optional language. "Shall" is mandatory. A vessel proceeding in fog with engines on slow ahead but not immediately available for a crash-back is not in compliance.

---

Due Regard for Rules 4 Through 10 — Rule 19(c)

Every vessel shall have due regard to the prevailing circumstances and conditions of restricted visibility when complying with Rules 4 through 10. 33 CFR §83.19 Rules 4 through 10 cover general conduct, lookout, safe speed, risk of collision, action to avoid collision, narrow channels, and traffic separation schemes. Rule 19 does not suspend those rules — it requires that they be applied with heightened awareness of the degraded environment.

---

Radar-Only Detection — Rule 19(d)

When a vessel detects by radar alone the presence of another vessel, she shall determine whether a close-quarters situation is developing and/or risk of collision exists. 33 CFR §83.19 If either condition is found to exist, she shall take avoiding action in ample time. 33 CFR §83.19

When that avoiding action consists of an alteration of course, the following shall, so far as possible, be avoided:

1. An alteration of course to port for a vessel forward of the beam, other than for a vessel being overtaken. 33 CFR §83.19 2. An alteration of course toward a vessel abeam or abaft the beam. 33 CFR §83.19

These two prohibitions are the most heavily tested elements of Rule 19. Understand the geometry:

• A contact forward of the beam — do not turn to port (unless overtaking). A turn to starboard, or a reduction in speed, is the preferred action.
• A contact abeam or abaft the beam — do not turn toward it. Turning away or reducing speed is preferred.

The rule does not prohibit a speed reduction in either case; it specifically restricts only course alterations. A vessel may always reduce speed or stop. 33 CFR §83.19

---

Fog Signal Heard Forward of the Beam — Rule 19(e)

Rule 19(e) addresses the situation where a vessel hears — not detects by radar, but actually hears — the fog signal of another vessel apparently forward of her beam, or where she cannot avoid a close-quarters situation with a vessel forward of her beam. 33 CFR §83.19

In that circumstance, except where it has been determined that a risk of collision does not exist, the vessel shall:

1. Reduce her speed to the minimum at which she can be kept on course (bare steerageway). 33 CFR §83.19 2. If necessary, take all her way off. 33 CFR §83.19 3. In any event, navigate with extreme caution until danger of collision is over. 33 CFR §83.19

The only exception is where it has been determined — not merely assumed — that a risk of collision does not exist. 33 CFR §83.19 The burden of that determination rests on the vessel. If there is any doubt, the vessel must reduce speed.

---

Navigation Lights in Restricted Visibility

Although Rule 19 does not itself address lights, Rule 20 requires that navigation lights prescribed by the Rules shall, if carried, also be exhibited from sunrise to sunset in restricted visibility. 33 CFR §83.20 Candidates should connect these two rules: restricted visibility triggers both the conduct requirements of Rule 19 and the daytime light-exhibition requirement of Rule 20(c). 33 CFR §83.20

---

Why It Matters on the Exam

OUPV and Master 100 GT written exams consistently test Rule 19 in several ways:

1. Which rules apply when vessels are not in sight of one another? The answer is Rule 19, not Rules 11–18. Rules 11–18 apply only when vessels are in sight of one another. 33 CFR §83.11 33 CFR §83.19 Confusing these two regimes is the single most common error on this topic.

2. What is the specific engine requirement for power-driven vessels in restricted visibility? Engines shall be ready for immediate maneuver. 33 CFR §83.19 The exam may offer "slow ahead," "half ahead," or "engines warmed up" as distractors. Only "ready for immediate maneuver" is correct.

3. What course alterations are prohibited when a radar contact is forward of the beam? An alteration to port, unless the contact is being overtaken. 33 CFR §83.19 The exam will present scenarios with contacts at various bearings and ask which action is prohibited or preferred.

4. What is required when a fog signal is heard forward of the beam? Reduce to minimum speed at which the vessel can be kept on course; if necessary, take all way off; navigate with extreme caution. 33 CFR §83.19 The exam may ask whether a vessel must stop — the answer is "if necessary," not automatically.

5. What does "restricted visibility" include? Fog, mist, falling snow, heavy rainstorms, sandstorms, or any other similar causes. 33 CFR §83.03 Heavy rain qualifies. Darkness alone does not.

---

Common Pitfalls

Pitfall 1 — Applying Rules 11–18 in restricted visibility. Rules 11–18 (crossing, head-on, overtaking, give-way, stand-on) apply only when vessels are in sight of one another. 33 CFR §83.11 In fog, there is no "give-way vessel" and no "stand-on vessel" in the Rules 11–18 sense. Rule 19 is the governing rule. Candidates who try to apply crossing or head-on rules to a radar contact in fog are applying the wrong rule.

Pitfall 2 — Confusing "radar contact" with "in sight." "In sight of one another" requires visual observation. 33 CFR §83.03 A vessel seen only on radar is not in sight. This distinction determines which set of rules applies.

Pitfall 3 — Forgetting the "or near" language. Rule 19 applies when navigating in or near an area of restricted visibility. 33 CFR §83.19 A vessel approaching a fog bank must already be in compliance before she enters it.

Pitfall 4 — Misreading the port-alteration prohibition. The prohibition on altering course to port applies to a vessel forward of the beam. 33 CFR §83.19 For a vessel abeam or abaft the beam, the prohibition is on altering course toward that vessel — which could be either port or starboard depending on which side the contact is on. Do not memorize "never turn to port" as a blanket rule.

Pitfall 5 — Treating the fog-signal speed reduction as automatic. Rule 19(e) requires speed reduction when a fog signal is heard forward of the beam, except where it has been determined that a risk of collision does not exist. 33 CFR §83.19 The exception exists, but the burden of making that determination is on the vessel. In exam scenarios, assume the exception does not apply unless the question explicitly states that risk of collision has been ruled out.

Pitfall 6 — Overlooking the engine-readiness requirement. The requirement that a power-driven vessel have engines ready for immediate maneuver is separate from and in addition to the safe speed requirement. 33 CFR §83.19 Both must be satisfied simultaneously.

---

Quick Check

Q1 — Rule 19 applies to vessels in what condition relative to one another?

Rule 19 applies to vessels not in sight of one another when navigating in or near an area of restricted visibility. 33 CFR §83.19 "In sight" requires visual observation; radar contact alone does not satisfy that standard. 33 CFR §83.03

Q2 — Your power-driven vessel is proceeding in dense fog. What specific engine requirement does Rule 19 impose?

A power-driven vessel shall have her engines ready for immediate maneuver. 33 CFR §83.19 This is a mandatory requirement, not a recommendation.

Q3 — You detect a vessel by radar alone, bearing 030° relative (forward of the beam). A close-quarters situation is developing. Which course alteration is prohibited?

An alteration of course to port is prohibited for a vessel forward of the beam, other than for a vessel being overtaken. 33 CFR §83.19 An alteration to starboard or a reduction in speed would be the preferred avoiding action.

Q4 — You hear a fog signal apparently forward of your beam. Risk of collision has not been ruled out. What actions does Rule 19 require?

You shall reduce speed to the minimum at which the vessel can be kept on course; if necessary, take all way off; and in any event navigate with extreme caution until danger of collision is over. 33 CFR §83.19

Q5 — A radar contact is bearing 160° relative (abaft the beam, on the starboard quarter). What course alteration does Rule 19 prohibit?

An alteration of course toward a vessel abeam or abaft the beam is prohibited. 33 CFR §83.19 Since the contact is on the starboard quarter, an alteration to starboard (toward the contact) is the prohibited action.

Q6 — Does "restricted visibility" include heavy rain? What about darkness?

Yes, heavy rainstorms are expressly included in the definition of restricted visibility. 33 CFR §83.03 Darkness is not listed and does not constitute restricted visibility under the Rules.

Q7 — You are in fog and detect another vessel by radar on a bearing that creates a risk of collision. Which rules govern your conduct — Rules 11–18 or Rule 19?

Rule 19 governs. Rules 11 through 18 apply only to vessels in sight of one another. 33 CFR §83.11 A radar contact is not "in sight." 33 CFR §83.03 Rule 19 is the applicable rule for vessels not in sight of one another in or near restricted visibility. 33 CFR §83.19