Page 151 - Collision Avoidance Rules Guide

quarters situation when the two vessels are several miles apart so
that the vessel being overtaken will be relieved of her obligation to
take avoiding action and will be less likely to make a conflicting
manceuvre.
Alterations of course towards a vessel approaching from abeam or
abaft the beam are to be avoided. This means that alterations of
course to port should not be made to avoid a close quarters situation
with a vessel approaching from any direction on the port side or from
the starboard bow and that an alteration to starboard should not be
made for a vessel approaching from the starboard beam or starboard
quarter. An alteration in either direction is permitted when a vessel
approaches from astern.
The purpose of the requirement to avoid turning to port when a
close quarters situation is developing with a vessel forward of the
beam is to reduce the possibility of conflicting action being taken by
vessels on opposite or nearly opposite courses. A substantial alter-
ation of course to port to avoid a vessel approaching from just for-
ward of the starboard beam is a relatively safe manceuvre as the
difference between courses is likely to be less than 90”. The line of
demarcation between ‘abeam’ and ‘forward of the beam’ is not speci-
fied so an alteration to port to avoid a vessel approaching from
within about two points of the starboard beam would not be a clear
contravention of Rule 19(d). When vessels are in sight of one another
a power-driven vessel is permitted to make a substantial alteration of
course to port to avoid another power-driven vessel approaching
from just forward of the starboard beam as such action would not
involve crossing ahead of the other ship.
Provision is made in Rule 19(d) for exceptions to the restrictions
on course changes by the inclusion of the words ‘so far as possible’.
However, if an alteration to port is decided upon, due perhaps to lack
of sea room to starboard or to the presence of other vessels, it is espe-
cially important that it should be made as early as possible and that
it should be a bold alteration when avoiding a close quarters situation
with a vessel approaching from ahead or fine on the bow.

Change of speed to avoid a close quarters situation
Avoiding action must be taken if a close quarters situation is devel-
oping and there is risk of collision but a change of speed can be made
as an alternative to, or in association with, an alteration of course.
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