Page 148 - Collision Avoidance Rules Guide

comes into visual sight, or if a fog signal is heard forward of the
beam, the appropriate Rule must be complied with. It is essential to
keep a good look-out by sight and hearing in addition to making
proper use of the radar.

Determine risk of collision
A vessel which detects another vessel by radar alone in restricted
visibility is required to determine whether a close quarters situation
is developing and/or risk of collision exists. Rule 7(b) also requires
that proper use be made of radar equipment to obtain early warning
of risk of collision, and that radar plotting or equivalent systematic
observation should be carried out. Assumptions must not be based on
scanty information (see pages 43-5).
A close quarters situation

Rules 8(c), 19(d) and 19(e) refer to a close quarters situation. The
distance at which a close quarters situation first applies has not been
defined in miles, and is not likely to be, as it will depend upon a num-
ber of factors. The 1972 Conference considered the possibility of
specifying the distance at which it would begin to apply but after a
lengthy discussion it was decided that this distance could not be
quantified.

Grepa-Verena
It leaves open to argument what is meant by the phrase ‘close quarters situ-
ation’. That, I think, must depend upon the size, characteristics and speed of
the ships concerned. I think, however, that in the case of ships of the class
that we have here it must mean a quite substantial distance, and, I would
venture to think, a distance measurable in miles rather than in yards. (Lord
Justice Willmer, 1961)
In restricted visibility, in the open sea, a close quarters situation is
generally considered to begin to apply at a distance of at least 2 miles
in any direction forward of the beam as this is the typical range of
audibility for the whistle of a large vessel in still conditions (see
Annex III(l)(c)). A minimum distance of 3 miles is sometimes sug-
gested when determining whether a close quarters situation is devel-
oping as allowance should be made for the effects of errors in radar
observations, especially at long range. However, distances of less than
2 miles may be considered sufficient when proceeding at reduced

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