Part B — Steering and Sailing Rules, Section III
COLREGS Rule 19 — Conduct of Vessels in Restricted Visibility
Rule 19 applies to vessels not in sight of each other when navigating in or near an area of restricted visibility. The normal stand-on/give-way framework of Rules 13–18 is suspended — every vessel proceeds at a safe speed adapted to the conditions, and specific radar and sound-signal actions are required.
Rule Text
Every vessel shall proceed at a safe speed adapted to the prevailing circumstances and conditions of restricted visibility. A vessel which detects by radar alone the presence of another vessel shall determine if a close-quarters situation is developing or risk of collision exists. If so, she shall take avoiding action in ample time. Avoiding action shall not consist of an alteration of course to port for a vessel forward of the beam, other than for a vessel being overtaken, and shall not consist of an alteration of course towards a vessel abeam or abaft the beam. A vessel which hears apparently forward of her beam the fog signal of another vessel shall reduce her speed to the minimum at which she can be kept on her course and shall navigate with extreme caution until the danger of collision is over.
What it means on the water
- →Applies when vessels are NOT in sight of each other — could be fog, smoke, heavy rain, or night.
- →Stand-on/give-way rules (13–18) do NOT apply in restricted visibility.
- →Every vessel proceeds at a safe speed adapted to restricted visibility conditions.
- →Hear a fog signal forward of the beam: reduce to minimum steerage speed, navigate with extreme caution.
- →Detect a vessel by radar forward of the beam: take avoiding action in ample time.
- →Do NOT alter course to PORT for a vessel detected forward of the beam (exception: overtaking).
- →Do NOT alter course toward a vessel abeam or abaft the beam.
Common exam mistakes
- ✗Applying the normal crossing/head-on rules in restricted visibility — Rule 19 replaces them.
- ✗Forgetting the prohibition on altering course to PORT for a radar contact forward of the beam.
- ✗Confusing 'safe speed' with 'slow speed' — minimum steerage speed is only required when you HEAR a fog signal forward of the beam.
USCG exam questions — Rule 19
These questions are drawn from the same pool used in real USCG licensing exams. Correct answers and explanations are shown.
1. Rule 19 applies to vessels in or near an area of restricted visibility. Which of the following is the primary speed requirement under Rule 19?
- A.A vessel shall proceed at bare steerageway
- B.A vessel shall proceed at a safe speed adapted to the prevailing circumstances✓
- C.A vessel shall reduce speed to dead slow ahead
- D.A vessel shall stop engines until visibility improves to at least 1 nautical mile
Why: Rule 19(b) requires vessels in or near restricted visibility to proceed at a safe speed — the same standard as Rule 6, but now critically important in fog. There is no prescribed absolute speed. The right speed depends on radar range, traffic, maneuverability, and sea state. Bare steerageway or dead slow may be appropriate but are not mandated.
2. In restricted visibility, which vessels sound one prolonged blast followed by TWO short blasts every 2 minutes?
- A.Power-driven vessels making way
- B.Power-driven vessels stopped and not making way
- C.Not Under Command, RAM, constrained by draft, sailing, fishing, or towing/pushing vessels✓
- D.Vessels at anchor
Why: Rule 35(c) assigns one prolonged blast followed by two short blasts to: vessels not under command (NUC), vessels restricted in ability to maneuver (RAM), vessels constrained by their draft, sailing vessels, fishing vessels, and vessels towing or pushing another vessel. All share this signal when underway in restricted visibility.
3. A vessel under 12 meters at anchor in restricted visibility — is she required to sound the bell signals of Rule 35(g)?
- A.Yes, same requirements apply to all vessels
- B.No, vessels under 12 meters are exempt but must make some efficient sound signal every minute✓
- C.No, vessels under 12 meters need not sound any signal when at anchor
- D.Yes, but she may substitute a whistle for the bell
Why: Rule 35(k) exempts vessels of less than 12 meters in length from the fog signals in Rule 35(g) (anchor bell) and 35(h) (aground), but they shall make some other efficient sound signal at intervals of not more than 2 minutes. The intent is flexibility for small craft that may lack a bell.
4. A 120-meter vessel is at anchor in restricted visibility. How must she supplement the forward bell signal?
- A.She sounds one prolonged blast after the bell
- B.She sounds three short blasts after the bell
- C.She strikes a gong rapidly in the after part immediately after ringing the forward bell✓
- D.She sounds a whistle signal in addition to the bell
Why: Rule 35(g) states that for vessels 100 meters or more in length, the bell is rung rapidly for 5 seconds in the forepart of the vessel, and a gong is struck rapidly for 5 seconds in the after part immediately after the bell. This gives anchored vessels in fog a forward and aft audio signal so approaching vessels can determine their aspect.
5. In restricted visibility, a vessel not under command, restricted in her ability to maneuver, sailing, or fishing shall sound which fog signal?
- A.One prolonged blast every 2 minutes
- B.Two prolonged blasts every 2 minutes
- C.One prolonged and two short blasts every 2 minutes✓
- D.Three short blasts every 2 minutes
Why: Rule 35(c) requires vessels not under command, restricted in ability to maneuver, constrained by draft, sailing, fishing, or towing/pushing to sound one prolonged followed by two short blasts at intervals of not more than 2 minutes.
6. Which of the following is NOT a factor a vessel must consider when determining a safe speed under Rule 6 in restricted visibility?
- A.State of visibility
- B.Traffic density
- C.The flag state of other vessels in the area✓
- D.The stopping distance and turning ability of the vessel
Why: Rule 6 lists factors for safe speed including visibility, traffic density, vessel maneuverability, background light at night, state of wind/sea/current, draft relative to water depth, and radar characteristics. The flag state of other vessels is irrelevant to safe speed determination.
7. Which vessel in restricted visibility is required to sound a fog signal of one prolonged blast at intervals not exceeding 2 minutes?
- A.A vessel at anchor
- B.A power-driven vessel making way through the water✓
- C.A vessel towing another vessel
- D.A sailing vessel underway
Why: Rule 35(a) requires a power-driven vessel making way through the water to sound one prolonged blast at intervals not exceeding 2 minutes. Sailing vessels and towing vessels use different signals (one prolonged and two short blasts).
8. A vessel less than 12 meters in length in restricted visibility is NOT required to give the prescribed fog signals under Rule 35, but shall make:
- A.At least one prolonged blast every 3 minutes
- B.Some other efficient sound signal at intervals of not more than 2 minutes✓
- C.Continuous sounding of a horn or whistle at slow intervals
- D.No sound signal is required for vessels under 12 meters
Why: Rule 35(i) states that a vessel of less than 12 meters in length shall not be obliged to give the prescribed fog signals but shall make some other efficient sound signal at intervals of not more than 2 minutes.
Frequently asked questions
- What should you do if you hear a fog signal forward of the beam in restricted visibility?
- Rule 19 requires you to immediately reduce to the minimum speed at which you can maintain steerage, and navigate with extreme caution until the danger of collision is over. You cannot determine the type, position, or course of the other vessel from a sound signal alone.
- Does the normal give-way/stand-on hierarchy apply in restricted visibility?
- No. In restricted visibility under Rule 19, vessels cannot be in sight of each other, so the crossing, head-on, and overtaking rules (13–17) and the responsibility hierarchy (Rule 18) do not apply. Every vessel must proceed at a safe speed, maintain a proper look-out, and take action based on radar detection or sound signals.
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