Page 71 - Collision Avoidance Rules Guide

(c) Alteration of course alone
Paragraph (c) is similar to Recommendation 5 of the Annex to the
1960 Rules but is now applicable in all conditions of visibility. In the
1960 Regulations the term 'close quarters situation' was only used
in Rule 16(c) and the Annex in relation to vessels using radar
in restricted visibility. The distance at which a close quarters situa-
tion first applies will depend upon a number of factors, including the
visibility.
In the open sea distances of the order of 2 to 3 miles are usually
considered as the outer limits in restricted visibility but smaller dis-
tances, probably of the order of 1 mile, would probably be accepted
for vessels in sight of one another (see also pages 129-30).
An alteration of course will be more effective than a change of
speed in order to avoid a vessel which is ahead or fine on the bow and
this will also apply if action has to be taken to avoid an overtaking
vessel approaching from astern or fine on the quarter which fails to
keep out of the way. A change of speed is more effective than an
alteration of course in order to avoid a vessel approaching from
abeam or near the beam, but an alteration of course can be made to
achieve the same result as a reduction of speed provided it is sub-
stantial. The diagram shows the effectiveness of turning over 60" to
port to avoid a vessel approaching on a constant bearing from the
starboard beam. It is usually safer to turn away from a vessel
approaching from that direction (see also pages 229-32).

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