Page 94 - Collision Avoidance Rules Guide

amount of crossing traffic. There can be little justification for crossing
the relatively short traffic lanes which have been established off capes
and headlands in many areas.
Crossing a traffic lane may disturb the traffic flow pattern and
increase the risk of collision. When risk of collision exists between
vessels in a traffic lane the relevant Rule from Part B will usually
apply, although small vessels and sailing vessels have a general obli-
gation to avoid impeding the safe passage of power-driven vessels
following the lane. A power-driven vessel, proceeding along a traffic
lane, which sees another power-driven vessel crossing from her own
starboard side will usually be required to keep clear by Rule 15. It
may be difficult for such a vessel to take substantial avoiding action
without making it necessary for other vessels to maneuvre.
The requirement to cross as nearly as practicable at right angles to
the general direction of traffic flow applies at all times, whether there
are vessels proceeding along the lane or not.

The words 'on a heading' were added to Rule 1O(c) by the 1987
amendments to make it clear that it is the heading of the vessel and
not the course made good which should be as nearly as practicable at
right angles to the direction of traffic flow. For slow vessels experi-
encing a strong cross current or tidal stream there can be an appre-
ciable difference between the course steered and the course made
good. The shortest time to cross a traffic lane is achieved by crossing
on a heading at right angles to the direction of traffic flow.
A vessel will only be justified in crossing a lane at an angle which
differs appreciably from 90" if there are special circumstances such
as the need to keep clear of another vessel or severe weather condi-
tions. A sailing vessel may be unable to cross at right angles because

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