Page 30 - CHIRP annual digest 2016.pdf

CHIRP Maritime

CHIRP noted that Singapore since 2011has advised that The underlying principle
three all-round green lights in a vertical line should be Safely cross a TSS by anticipating timely crossing of a lane,
displayed by vessels, to indicate their intention to cross matched to a predicted safe gap in traffic to ensure
the TSS. This signal will allow other vessels in the maximum bow crossing range (BCR) with opening
appropriate lanes to take actions if required and hence bearings of oncoming traffic, leaving no doubt of intention
enhance navigational safety. The IMO Assembly Resolu - and avoid a close quarters situation developing.
tion agreed that this signal could be recognised.
Discussion now concerns whether to insert a requirement Planning
into COLREGS Rule 10. ■ Use the Automatic Rader Plotting Aid (ARPA) to plot
The above article was published in MFB45 ALL oncoming lane vessels you will need to cross a
long distance ahead.
A General Comment on Traffic ■ Use the Time to Closest Point of Approach (TCPA)

Separation Schemes function to determine both yours and their ETA at the
initial point of crossing at current speeds.
The key message is: don’t become too ‘comfortable’ in
■ Note that immediately recognised gaps in advance
TSSs. High densities of large, deep draught, heavy dis - will change due to the differing speeds of the variety
placement ships – often at high speed, and often mixed
of oncoming traffic. Obvious gaps may disappear by
with many other types of craft with differing manoeuvring the time you arrive and others open up. The biggest
characteristics – heightens the risk of collision. Things can
gap will be where the difference in TCPAs of oncoming
change and develop fast. If, for example, we don’t notice traffic and your own vessel are GREATEST.
an unexpected speed or course change almost imme -
■ The use of True Motion (TM) ARPA vectors assists
diately, collision can become inevitable or nearly inevitable greatly in anticipating TSS traffic movements.
very quickly and at considerable range. A VLCC may take
■ Use of Trial Manoeuvre function on the ARPA will
5 nautical miles to come to a dead stop, require 2 nautical assist you in identifying this safe BCR emerging gap
miles each of advance and transfer for a significant turn,
in oncoming traffic in the lane.
take 20 minutes or so to apply astern revolutions from
■ To allow the safest gap in TSS traffic for crossing then
service speed, and become almost entirely unmanoeu -
consider EARLY adjustment of own ship speed to
vrable once committed to a first major manoeuvre. Never enable timely arrival for the largest TSS gap in traffic
relax vigilance.
to be created.
The above article was published in MFB42
Monitoring
Article. 26
■ If following a lane already and intending to cross the
Advisory Board Insight: Crossing other slowly make your course towards the edge of
Traffic Separation Scheme (TSS) Best the traffic separation zone on the nearest side to the
Practice other lane you intend to cross. Manage overtaking
situations you are in to safely achieve it. This should
Safely crossing a congested TSS can be one of the most
challenging navigational manoeuvres we undertake at sea. mean any traffic overtaking your own ship at the
point of crossing the TSS will always be on the far side
We all know that the COLREGS Rule 10 applies but
experience has shown CHIRP the application of few of you and away from the start of your crossing turn.
■ Monitor TCPAs of oncoming traffic in the opposite
underlying principles considerably reduces the stress of
this evolution, improves safe passing distances and adds a lane you will need to cross continually for pre -
dictability according to your plan. They can and will
layer of professionalism in the execution of safely crossing
a TSS. change if the other vessel acts differently than
predicted and your TSS crossing plan may then have
The following has drawn on a selection of professional to change.
mariners’ experiences and may be equally applied in all ■ Use Automatic Identification System (AIS) but with
crossing TSS scenarios from the full routing, merging with caution. The key vessels you will need to cross ahead
a lane or indeed moving from one lane to cross another of may be interrogated on AIS for destination and ETA.
within the length of routing such as to a pilot station to This will help you firm your crossing plan if it confirms
maintain a booked ETA for example. what you predict and they are continuing within the

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