Page 149 - Collision Avoidance Rules Guide

speed in congested waters, when in an overtaking situation, or, when
a vessel is expected to pass astern.

Taking avoiding action in ample time
Avoiding action must be taken if a close quarters situation is develop-
ing and/or risk of collision exists. It is not necessary to take avoiding
action if a vessel is expected to pass at a close distance but there is no
risk of collision as, for instance, when two vessels are proceeding in
opposite directions on their correct sides within a narrow channel.
Rule 8(a) requires avoiding action to be taken in ample time in all
conditions of visibility. When the visibility is restricted it is generally
necessary to take action to avoid a close quarters situation at an ear-
lier stage. However, action should not be taken without first making
a full assessment of the situation. Rule 7(c) states that assumptions
shall not be made on the basis of scanty information, especially
scanty radar information.
As a general guide it has been suggested that, using a 12 mile
range scale in the open sea, radar observations should be assessed as
an approaching target crosses the outer one third of the screen to see
whether a close quarters situation is developing. If so substantial
action should be taken before the target reaches the inner one third of
the screen.
Rule 19(d) requires avoiding action to be taken in ample time if a
close quarters situation is developing with a vessel approaching from
any direction. A vessel which is being overtaken is not required, or
even permitted, to keep her course and speed when a close quarters
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