Part B-IIICritical
Rule 19: Conduct in restricted visibility
In restricted visibility without visual contact, navigate defensively with radar discipline and immediate readiness.
Detailed Explanation
Restricted visibility demands defensive navigation: assume risk exists, reduce speed, and act with ample time to spare.
A
Applies when vessels are not in sight of one another in/near restricted visibility.
B
Proceed at safe speed adapted to conditions; power-driven vessels keep engines ready for immediate manoeuvre.
C
Apply Section I with due regard to restricted-visibility conditions.
D
If detecting by radar alone, assess close-quarters/risk early and act in ample time. Avoid, as far as possible
- (i)alteration to port for vessel forward of beam (except overtaken)
- (ii)alteration toward vessel abeam/abaft beam.
E
Unless risk is determined absent: if fog signal is heard apparently forward of beam, or close-quarters forward of beam cannot be avoided, reduce to minimum speed for steerage, take all way off if needed, and navigate with extreme caution.
Key Points
- Applies when vessels are NOT in sight in restricted visibility
- Avoid altering to port for a vessel forward of the beam
- Avoid altering toward a vessel abeam or abaft the beam
- Speed must allow stopping within visible distance
Examples
- In dense fog you detect a radar target 4 miles ahead, 10° on your port bow. Rule 19(d)(i) prohibits altering to port for a vessel forward of your beam — you alter to starboard instead.
- Your engines are on standby as you navigate in restricted visibility. You hear a fog signal that appears to be forward of your beam but cannot localise it. Under Rule 19(e), you reduce to bare minimum steerage way.
- A container ship detects a vessel on radar abeam to starboard, range closing. Rule 19(d)(ii) advises against altering course toward a vessel abeam or abaft the beam; the ship reduces speed instead.
Common Mistakes
- Altering course to port for a vessel detected by radar forward of the beam.
- Failing to have engines ready for immediate manoeuvre in restricted visibility.
- Altering course towards a vessel abeam or abaft the beam, contrary to Rule 19(d)(ii).