Page 136 - Collision Avoidance Rules Guide

able to reduce her speed. A vessel engaged in a special operation
which cannot conveniently alter course or speed could request the
other vessel to keep out of the way but must take avoiding action if
the request is not complied with. The vessel being overtaken could
comply with such a request as she is permitted by Rule 17(a)(ii) to
take action to avoid collision by her own manceuvre when it becomes
apparent that the overtaking vessel is not taking appropriate action.

Categories of vessels
A vessel may only be justified in regarding herself as falling within
a certain category of privileged vessels for the purpose of Rule 18 if
she satisfies the conditions of the relevant definition of Rule 3 and is
also showing the lights or shapes prescribed in the appropriate Rule
of Part C. A vessel engaged in a towing operation is not privileged
with respect to other vessels unless she is severely restricted in her
ability to deviate from her course.
Some vessels may not be easily identified as being of a special
category and, by day, their shapes may not be sighted and recognized
by other vessels in time for early avoiding action to be taken. This is
more likely to apply if the hampered vessel is proceeding at high
speed and the two vessels are meeting nearly end-on. In such
circumstances the privileged vessel must make the signals prescribed
in Rule 34(d) and take avoiding action, if possible, in accordance
with Rule 17(a)(ii) (see pages 106-8).

Action to be taken when Rule 18 applies
A vessel required to keep out of the way by this Rule must take early
and substantial action in accordance with Rule 16. She is not
required to avoid crossing ahead but action must be such as to result
in passing at a safe distance. It may be difficult for a hampered ves-
sel to take effective avoiding action to avoid another vessel in a more
privileged category but provision is made for such cases in the wording
of Rule 18(c) and (d).
The privileged vessel is required to keep her course and speed in
accordance with Rule 17(a)(i), so far as she is able to do so. The give-
way vessel must take into account the possibility that the nature of
the work being carried out, or the special circumstances which apply,
may make it impossible for the stand-on vessel to keep both course
and speed.

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