Page 73 - Collision Avoidance Rules Guide

requirement to check the effectiveness of action taken to avoid a
vessel which is in sight.
As risk of collision is deemed to exist if the compass bearing of an
approaching vessel does not appreciably change a definite and
continuing change of compass bearing would be one indication of the
initial effectiveness of the avoiding action. However, an appreciable
change of bearing may not be sufficient to establish that the vessels
will eventually pass clear of one another. Subsequent action by the
other vessel could result in renewed risk of collision. The situation
could become even more dangerous than before if both vessels turn
towards each other when crossing at a broad angle as the speed of
approach may be increased.
The need to check the effectiveness of action taken to avoid colli-
sion applies especially in restricted visibility as subsequent action by
the other vessel is less likely to be apparent on the radar screen.
Plotting, or equivalent systematic observation, should therefore be
continued until the other vessel is well clear.
When action is taken which could conflict with the action which is
likely to be taken by the other vessel particular care should be taken.
If, for instance, speed is reduced to avoid a vessel crossing from the
port bow, a careful watch should be kept to see if the other vessel
turns to starboard as this would probably necessitate a return to the
original speed.

(e) Reductions of speed

This paragraph combines the provisions of Rule 23 and
Recommendation 8 of the Annex to the 1960 Regulations. It now
applies to all vessels, whereas Rule 23 of the previous Regulations
applied only to power-driven vessels. A new provision is that a
reduction of speed is required, if necessary, to allow more time to
assess the situation.
Rule 8(e) must be interpreted in context with Rules 6, 19(b) and
19(e). Every vessel is required to proceed at a safe speed at all times.
Although increases of speed, as a means of avoiding collision, are
not prohibited, the emphasis in the Rules is placed on reductions of
speed. As vessels infrequently proceed at a lower speed than would
be considered safe for the prevailing circumstances an increase in
speed large enough to satisfy the requirements of Rule 8(b) would
usually be in contravention of Rule 6.
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