Page 163 - Collision Avoidance Rules Guide

must be fitted with inboard screens in accordance with Annex I(5) to
give a practical cut-off between 1" and 3" outside the prescribed
sector, as specified in Annex I(9)(a). This means that the rays of light
from the outer part of the filament, or wick, may cross the fore and
aft line and be visible to a vessel approaching from an angle of up to
3" on the opposite bow. If some of the light were not permitted to
show across the bow there would be a theoretical 'dark lane' ahead
which could result in vessels meeting exactly end-on being unable to
see each other's sidelights.

Sternlight
This definition is based on Rule 10(a) of the 1960 Regulations. The
light is now required to be placed 'as nearly as practicable at the
stem' as some vessels such as towing vessels, stem trawlers and LASH
vessels with an open stern could find it difficult or even impossible
to carry a light at the stern.

Towing light
This light is prescribed only for a vessel engaged in towing another
vessel from the stem. It is a new provision.
The 1960 Regulations prescribed only three colours of light: red,
green and white. In the 1972 Regulations both the towing light and
the flashing light of an air-cushion vessel are required to be yellow
and Annex I1 permits vessels fishing with purse seine gear to exhibit
two yellow lights which flash alternately. Consideration was given to
the possibility of using yellow for a stern light but tests indicated that
yellow and white lights are not distinguishable unless they are in jux-
taposition. The yellow towing light is required to be carried above the
white stem light.
Vessels towing a dracone were previously required to exhibit a blue
light but lights of this colour are not prescribed by the 1972 Regulations
as the range of visibility was considered to be too limited.

All-round light
It may not be possible to show an unbroken light over an arc of the
horizon of 360". This definition is further qualified by paragraph 9(b)
of Annex I which requires all-round lights, other than anchor lights,
to be so placed as not to be obscured within angular sectors of more
than 6".
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