Page 72 - Collision Avoidance Rules Guide

(d) Passing at a safe distance
The requirement that action taken to avoid collision shall be such as
to result in passing at a safe distance is introduced for the first time
in the 1972 Regulations. When vessels are in sight of one another,
and one of two vessels is required to keep out of the way, the obliga-
tion to take action which will result in passing at a safe distance will
obviously apply almost exclusively to the give-way vessel.
The stand-on vessel must initially keep her course and speed, and
is only permitted to take action by Rule 17(a)(ii) when it becomes
apparent to her that the vessel required to keep out of the way is not
taking appropriate action. The first moment for such permitted action
may not be at a sufficiently early stage to ensure that her manmuvre
alone will achieve a really safe passing distance. It is therefore
unlikely that the requirement of Rule 8(d) will be considered to apply
to action permitted by Rule 17(a)(ii). The requirement could also
hardly apply to action taken by the stand-on vessel in accordance with
Rule 17(b) when the vessels are so close that collision cannot be
avoided by the action of the give-way vessel alone. This is implied by
the wording of the Rule which says that the stand-on vessel shall take
such action as will best aid to prevent collision. The circumstances of
the case must be taken into account.
In restricted visibility every vessel which detects the presence of
another vessel by radar is required to take avoiding action if a close
quarters situation is developing and/or risk of collision exists
(Rule 19(d)), but the circumstances may not permit action to be taken
which will result in passing at a safe distance. If, for instance in the
open sea, a ship is detected ahead or fine on the bow and careful plot-
ting or equivalent method of assessment indicates that the other
vessel is proceeding at a relatively high speed, and that if no action
is taken the two vessels will pass starboard to starboard at too close
a distance, of the order of 1 mile, it may be dangerous to alter course
either to starboard or to port. A reduction of speed may be the safest
form of action in such circumstances but this may not appreciably
affect the passing distance.

Effectiveness of action to be checked
The second sentence of paragraph (d) is similar to the first part of
Recommendation 4 of the Annex to the 1960 Regulations. However,
it is now of general application, which means that there is also a
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