Rule 7 explains how to decide whether risk of collision exists. Every vessel shall use all available means appropriate to the prevailing circumstances and conditions to make that assessment. If there is any doubt, such risk shall be deemed to exist.
IMO COLREG 1972Official text
(a) Every vessel shall use all available means appropriate to the prevailing circumstances and conditions to determine if risk of collision exists. If there is any doubt such risk shall be deemed to exist.
(b) Proper use shall be made of radar equipment if fitted and operational, including long-range scanning to obtain early warning of risk of collision and radar plotting or equivalent systematic observation of detected objects.
(c) Assumptions shall not be made on the basis of scanty information, especially scanty radar information.
(d) In determining if risk of collision exists the following considerations shall be among those taken into account:
(i) such risk shall be deemed to exist if the compass bearing of an approaching vessel does not appreciably change;
(ii) such risk may sometimes exist even when an appreciable bearing change is evident, particularly when approaching a very large vessel or a tow or when approaching a vessel at close range.Reproduced verbatim from the IMO COLREG 1972 Convention (as amended).
STCW Bridge Watch Lens
Decide applicability before manoeuvring: Rules 4-10 apply in any visibility, Rules 11-18 only when vessels are in sight, and Rule 19 governs radar-only encounters in restricted visibility.
Build the traffic picture with sight, hearing, radar/ARPA and chart context.
Do not let AIS or one isolated bearing replace systematic observation.
After manoeuvring, keep monitoring bearing, range, CPA/TCPA and passing distance until the other vessel is finally past and clear.
Exam Focus
Start every scenario by classifying the encounter: overtaking, head-on, crossing, narrow channel, traffic separation, or restricted visibility.
If two rules seem to conflict, check the order carefully: overtaking duties still apply, and Rule 2 still requires ordinary seamanship.
Steady or nearly steady bearing is the classic trigger, but close range, a large vessel or a tow can still mean risk even when bearing change seems small.
Βασικά σημεία
A steady or nearly steady bearing is a classic collision-warning sign
If there is doubt, the Rules tell you to treat the risk as real
Scanty radar information is not a safe basis for assumptions
Radar must be used systematically, not casually
Συνηθισμένα λάθη
Assuming a slight bearing drift means there is no danger
Failing to plot or systematically track a target before deciding the situation is safe
Treating AIS data as if it replaces Rule 7 assessment
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