Page 49 - Collision Avoidance Rules Guide

The reference to draught is intended to cover the possible restriction
of manmuvring space due to shallow water in the vicinity, or the hydro-
dynamic effects, such as bow cushion, bank suction and interaction
between ships, which can generally be eliminated or reduced by a
reduction of speed.

Additionally, by vessels with operational radar
From the context of the Rule it is apparent that the term ‘operational
radar’ means radar in use. However, it must be appreciated that radar
is required to be used, when appropriate, both for keeping a proper
look-out and for determining risk of collision (see Rules 5 and 7)
provided, of course, that it is in working order.
In restricted visibility a vessel making proper use of radar will nor-
mally be justified in going at a higher speed than that which would be
acceptable for a vessel which does not have the equipment but not
usually at the speed which would be considered safe for good visibil-
ity (see the example on page 28). Rule 6(b) requires several factors to
be taken into account. Some of the factors were included in the Annex
to the 1960 Regulations which merely gave recommendations on the
use of radar information as an aid to the avoidance of collision.

Characteristics, eficiency and limitations
A considerable choice of radar equipment is available ranging from the
relatively small, low cost, installations which are intended for use on
small vessels to the highly sophisticated computer-aided systems fitted
to some of the larger ships. Even the most efficient equipment cannot
be regarded as a complete substitute for the human eye. Radar may fail
to detect small targets, alterations of course made by other vessels are
usually less apparent and the use of radar bearings is more likely to
result in a faulty appreciation of risk of collision than visual bearings
taken by compass. However, the use of radar in clear visibility does
give some advantages such as range indication and, with some
systems, the prediction of the distance of nearest approach and an indi-
cation of the effectiveness of proposed manceuvres to avoid collision.
All vessels of 10,000 gross tons and upwards are required to be fit-
ted with automatic radar plotting aids (ARPA) by the IMO Safety of
Life at Sea (SOLAS) Convention. Such equipment is being fitted to an
increasing proportion of smaller ships. When advanced equipment of
this type is provided it is expected to be put to effective use.

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