COLREGS 16: Rule 19
Part III: Conduct of vessels in restricted visibility contains only one rule: Rule 19. This article gives an in-depth explanation of the application of the Rule, along with examples of how to answer Rule 19 questions and a handful of examples, including the ‘no common alteration’ scenario.
Relevant documents and M-notices: MSN 1781, MGN 369
Parts (a) to (c) of Rule 19 can be thought of as the ‘general’ parts of the rule.
Rule 19 - Conduct of vessels in restricted visibility (a)
This Rule applies to vessels not in sight of one another when navigating in or near an area of restricted visibility.
First off, what is restricted visibility? From Rule 3 - General definitions:
The term “restricted visibility” means any condition in which visibility is restricted by fog, mist, falling snow, heavy rainstorms, sandstorms or any other similar causes.
Not every collision situation that occurs in restricted visibility is a Rule 19 situation, though; if you can see the other vessel, it is not a Rule 19 situation.
Also from Rule 3 - General definitions:
Vessels shall be deemed to be in sight of one another only when one can be observed visually from the other.
The corollary to this is also true; vessels are not in sight of one another when one cannot be observed visually from the other.
There is, therefor, a degree of subjectivity in deciding when a vessel is in restricted visibility. To consider a slight haze that might reduce visibility from twelve miles to ten as restricted visibility would be a stretch of the imagination. A dense fog, however, that obscures your own jackstaff is clearly restricted visibility. Somewhere between these is a grey area, especially when there are no radar targets to use to determine the range of visibility. As a general rule, if you think the visibility is restricted, assume that it is.
Which rules apply when you cannot see the other vessel?
All the rules from Sections I and III. That is:
Rules 3-10
Rule 19
We won’t go into Rules 3-10 here. These were covered in earlier articles; re-read those if you need a reminder of the rules that apply in all conditions of visibility.
Rule 19 (b)
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.
This is largely a re-stating of Rule 6 - Safe Speed.
Every vessel shall have due regard to the prevailing circumstances and conditions of restricted visibility when complying with the Rules of Section I of this Part.
Remember that Section I (Rules to ) apply in all conditions of visibility. Think of part (b) of Rule 19, with its requirement to have engines ready for immediate manoeuvre, as an add-on. Safe speed should be under continuous review.
Rule 19 (c)
Every vessel shall have due regard to the prevailing circumstances and conditions of restricted visibility when complying with the Rules of Section I of this Part.
This refers, mostly, to Rules 5 - Lookout, 6 - Safe Speed and 7 - Risk of Collision. When in restricted visibility it is wise to post additional lookouts, or a radar watch. Safe speed will be reduced, and the appropriate means of assessing risk of collision will change slightly.
Now that the ‘general’ parts of Rule 19 are out of the way, we get to the ‘collision avoidance’ parts of the rule.
Rule 19 (d)
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:
(i) an alteration of course to port for a vessel forward of the beam, other than for a vessel being overtaken;
(ii) an alteration of course towards a vessel abeam or abaft the beam
What is a close-quarters situation? We’re familiar with risk of collision, but this is new. From MGN 369:
Similar to ‘safe speed’, a ‘close-quarters situation’ depends on the particular circumstances and closing speeds of the vessels involved. Manoeuvring characteristics, visibility, weather, traffic density and restricted or open waters, will all have an influence on determining at what distance a close-quarters situation is deemed to exist. A close-quarters situation is not to be confused with a risk of collision which begins at an earlier point in time.
If you detect a vessel by radar alone, you cannot see it. The questions that lead us into ROC ROA SMR for a Rule 19 situation are:
Have I detected it by radar? Yes
Can I see it? No
Is a close-quarters situation developing/does risk of collision exist? Yes (we’ll talk more about radar plotting later).
Time to take avoiding action.
Rule 19 (d) states that, when taking avoiding action by altering course, so far as possible the following shall be avoided:
An alteration of course to port for a vessel forward of the beam other than for a vessel being overtaken
An alteration of course towards a vessel abeam or abaft the beam
So, for a vessel forward of the beam, unless it is being overtaken, we should alter to starboard. But what, in the context of Rule 19, is a vessel being overtaken? Don’t quote the definition from Rule 13; this only applies when vessels are in sight of one another.
There is no common consensus on this. Some people say that if you are approaching the other vessel from abaft their beam then you are overtaking. Others say that you can assume that this is the same as the Rule 13 definition. There are some scenarios where you are very definitely overtaking, for example in the image below.
In this image the red arrows are true vectors and the red trail is a relative trail. So the vessel ahead of us is heading in the same direction we are and is being overtaken by us.
In a Rule 19 scenario, if you are in doubt as to whether you are overtaking, assume that you are not. This means you shouldn’t have to get into a discussion with the examiner over what overtaking means in a Rule 19 scenario. If in doubt, go to starboard.
For a vessel abeam or abaft the beam, we should alter course away from it.
Consider the four scenarios depicted in the image below (they aren’t all happening at the same time). This shows a simplified radar display, divided into quarters, with our vessel is in the centre. Assume that neither A nor D are being overtaken. For simplicity sake the red lines are relative vectors and there are no trails. Interpretation of radar displays will be covered in another article. For a reminder of radar setup for collision avoidance, see the following article:
Vessel A is forward of our beam and not being overtaken. We should alter to starboard.