Section III - Conduct of vessels in restricted visibility

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.

If a vessel looms into view through the mist, you are in sight of one another and must immediately begin to apply the Rules of Section II. You also use different sound signals. Later on we will learn the difference between the fog signals of Rule 35 and those of Rule 34 which apply only if you can see the other vessel

(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.

In restricted visibility, own ship’s manoeuvrability would be a major influence in choice of speed, including the ability to reduce speed immediately. On some vessels it may take several minutes to prepare the engines for manoeuvring, usually resulting in a slight fall in speed and fuel economy. Exactly how restricted the visibility must be to demand such action is not specified in the Rules and opinions vary. Depending on the stopping power and manoeuvrability of the ship it might be appropriate when visibility has fallen to about 5 miles in areas known to be subject to sudden onset of fog. This requirement also implies hand steering where auto-pilot is normally used.

(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.

The Rules of Section I are those which apply in ‘any visibility’. ‘Pay due regard’ means ‘give adequate attention to’. What this paragraph actually means is that we must give extra consideration to those Rules as a result of the poor visibility. The Rules of Section I particularly affected by this requirement are 5, 7 and 8 – Lookout, Risk of Collision and Avoiding Action. In other words we would be expected to post extra lookouts day or night, probably outside and maybe right forward, so that fog signals or engines of other vessels can be heard.

 
(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:
 

Not surprisingly, the courts have found that the phrase ‘close quarters situation’ is open to argument. Since fog signals (for vessels over 200 metres) have to be audible for 2 miles, this has become the generally accepted distance at which a close quarters situation might be said to begin. For smaller manoeuvrable vessels it could be considered rather less. If we keep to the fog signal analogy it would be half a mile for vessels below 20 metres.

For larger vessels in the open sea is has been suggested that using a 12-mile range scale, targets should be assessed while in the outer third of the screen and if a close quarters situation is developing, action should be taken before they reach the inner third. Smaller vessels might do likewise on a lower range scale.

It should always be remembered that small timber or fibreglass vessels often do not return an echo until they are quite close to the ‘searching’ radar, an area of the screen which may be obscured with sea clutter. A good radar lookout includes frequent changes of range to determine whether this is happening. Small vessels should deploy properly designed radar reflectors whenever possible.

On some large vessels, the conning position and radar scanner can be more than 200 metres from the bow. This creates a long ‘shadow’ sector where small craft can not be seen either visually or by radar.

 

There is no ‘stand-on’ or ‘give-way’ in Rule 19. That applies only when vessels are in sight of one another. In restricted visibility, every vessel must take avoiding action—not only if there is a risk of collision but also if a close quarters situation is developing. Close quarters situations can develop from astern as well as ahead.

(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.
The words ‘so far as possible’ are included in case an alteration to port is necessary due to lack of sea room or the presence of other vessels. Such action must be made as early as possible and as boldly as possible. ‘Abeam’ means at right angles anywhere along the ship’s length.
The words ‘so far as possible’ are included in case an alteration to port is necessary due to lack of sea room or the presence of other vessels. Such action must be made as early as possible and as boldly as possible. ‘Abeam’ means at right angles anywhere along the ship’s length.
 
 
 

There is no ‘stand-on’ or ‘give-way’ in Rule 19. That applies only when vessels are in sight of one another. In restricted visibility, every vessel must take avoiding action—not only if there is a risk of collision but also if a close quarters situation is developing. Close quarters situations can develop from astern as well as ahead.

(e)     Except where it has been determined that a risk of collision does not exist, every vessel which hears apparently forward of her beam the fog signal of another vessel, or which cannot avoid a close quarters situation with another vessel forward of her beam, shall reduce her speed to the minimum at which she can be kept on her course.  She shall if necessary take all her way off and in any event navigate with extreme caution until danger of collision is over.
 

The Rule phrases this in such a way as to emphasise that you have specifically determined by use of radar that there is no risk of collision, and ensured that any fog signals from forward of the beam have been positively identified and do not pose a threat – that they are, in fact, from the vessel which you think they are from, remembering that the direction of sound in fog can be very deceptive.

      It tells us exactly what to do if:

(1)  we hear a fog signal apparently forward of the beam

OR

(2)  we can not avoid a close quarters situation with another vessel forward of the beam.

      We must:

(1)  Reduce speed to steerage way

(2)  Take all way off if necessary, AND

(3)  Navigate with extreme caution.

Before altering course to avoid a collision, you need to know which way the other ship is heading with respect to your own vessel. This is called her aspect and it can not be determined from a fog signal. It is also difficult to determine quickly from a radar target. A radar plot as shown could represent a vessel with aspect Red 30º as sketched next to it.

On the other hand, it could also represent the two situations below.

 
      
 
 

If radar indicates an unavoidable close quarters situation with a vessel approaching from ahead or within about 30° of the bow, a vessel would be expected to reverse engines and take all way off, while remaining head on to the danger so as to present a smaller target.

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