Page 48 - Collision Avoidance Rules Guide

The above example has only been included to give some indica-
tion of how the Courts might interpret the term ‘safe speed’ for
different vessels. Too much importance should not be attached to the
specific values quoted as so much depends upon the circumstances
which apply in each particular case.
Attempts have been made to quantify speed in relation to the range
of visibility and other factors but discussions at the IMO meetings did
not result in an acceptable method of determining what value of
speed would be appropriate to the conditions. The list of factors to be
considered when determining a safe speed is intended to assist the
mariner by drawing attention to points which might otherwise have
been overlooked. The factors are not meant to be in order of import-
ance and the list is not exhaustive.

FACTORS TO BE TAKEN INTO ACCOUNT

By dl vessels
Most of the factors are generally self-evident. The state of visibility
is obviously of major importance. Rule 19 requires a power-driven
vessel to have her engines ready for immediate manceuvre in
restricted visibility and every vessel, when risk of collision exists, to
reduce her speed to the minimum at which she can be kept on her
course when a fog signal is heard forward of the beam, or when a
close quarters situation cannot be avoided with another vessel
forward of the beam. This Rule therefore places further limitations
on the value of safe speed in restricted visibility (see pages 125-28).
Information concerning stopping distances and turning circles is
now supplied to many vessels and navigating officers are expected to
be familiar with the manceuvring characteristics of their own ship.
The distance that a vessel will cover in a crash stop before being
brought to rest from full speed is likely to be between 5 and 15 ship
lengths, depending upon speed, displacement, type of machinery,
etc. Some general guidance on manceuvring characteristics is given
on pages 233-35.
The mancleuvrability is to be taken into account with reference to
the prevailing conditions. A vessel which is restricted in her ability to
manceuvre because of the nature of her work may not be justified in
going at a high speed in regions of high traffic density and when
approaching a relatively slow vessel so as to involve risk of collision.

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