Navigation in Restricted Visibility
Rule 19 applies to vessels not in sight of one another in or near restricted visibility. For a radar-only contact, Rule 19(d) qualifies the course alterations to avoid so far as possible, including the exception for a vessel being overtaken.
Operational Explanation
Rule 19 concerns vessels not in sight of one another when navigating in or near restricted visibility. Rule 19(d) has two distinct cautions: avoid, so far as possible, alteration to port for a vessel forward of the beam except when overtaking; and alteration towards a vessel abeam or abaft the beam. If actually in sight, apply the relevant Rules for vessels in sight.
Regulatory Reference
COLREG Rules 19 and 35: conduct and signals in restricted visibility. The category follows actual restriction of visibility, not darkness or adverse weather in isolation.
Assess the situation using all appropriate means and act in ample time; course-alteration cautions do not make another manoeuvre automatically safe. Apply Rule 35 signals appropriate to the vessel’s actual status. USCG: International Rules 19 and 35.
Scope of Application
Vessels not in sight of one another when navigating in or near restricted visibility. Radar acquisition alone does not make a vessel in sight.
Procedure / How to Complete It
- Determine whether the other vessel is actually in sight and which group of Rules applies.
- Proceed at safe speed and maintain an effective lookout; power-driven vessels must have engines ready for immediate manoeuvre.
- Use radar plotting/ARPA and all available means to assess collision risk.
- If action is a course alteration, avoid so far as possible port for forward of beam except overtaking and towards for abeam/abaft.
- Rule 19(e): unless collision risk has been ruled out, on hearing a fog signal apparently forward of the beam, or being unable to avoid close quarters with a vessel forward of the beam, reduce to minimum steerage speed; remove all way if necessary. Continue with extreme caution until the danger has passed.
Practical Example
A radar target forward of the beam does not create a generic prohibition on turning towards it: the textual caution is against alteration to port, except when overtaking. For a target abeam/abaft, avoid alteration towards it.
What Typically Goes Wrong
Reducing Rule 19(d) to do not alter towards a contact forward of the beam, omitting the second branch, or treating darkness as a standalone restricted-visibility category.
Common Mistakes Mistake Library
| Mistake | Consequence | How to Avoid It |
|---|---|---|
| Reducing Rule 19(d) to do not alter towards a contact forward of the beam, omitting the second branch, or treating darkness as a standalone restricted-visibility category. | Incorrect operational decision or regulatory status | Use the primary reference and ship-specific procedure |
What the PSCO Checks
Operational Tips
- State port/forward and towards/abeam-abaft separately.
- Do not confuse radar detection with in sight.
- Assess actual visibility, not time of day.
Preparation checklist
- In-sight status determined
- Safe speed and engines ready
- Continuous radar assessment without delaying necessary action
- Avoid port alteration so far as possible for a vessel forward, except one being overtaken
- Avoid alteration towards a vessel abeam or abaft so far as possible
- Rule 19(e) and Rule 35 ready
FAQ
Related Topics
Last substantive revision of this page: 15 September 2026 · page fingerprint 85ea35a7a534