The rules in this section apply in any condition of visibility, whether or not vessels can see each other.
Rule 4 - Application
The rules of this section apply to any condition of visibility.
Rule 5 - Look-out
Every vessel shall at all times maintain a proper look-out by sight and hearing as well as by all available means appropriate to the circumstances, so as to make a full appraisal of the situation and of the risk of collision.
Rule 6 - Safe speed
Every vessel shall proceed at a safe speed so she can take proper and effective action to avoid collision and be stopped within a distance appropriate to the circumstances. Factors to weigh:
- For all vessels: state of visibility; traffic density; the vessel's manoeuvrability, especially stopping distance and turning ability; at night, background light from shore or from the vessel's own lights; state of wind, sea and current, and proximity of navigational hazards; draught in relation to available water depth.
- Additionally for vessels with operational radar: the characteristics and limitations of the radar; constraints of the range scale in use; effect of sea state, weather and interference on detection; the possibility that small vessels, ice and other floating objects may go undetected; the number, location and movement of vessels detected.
Rule 7 - Risk of collision
Every vessel shall use all available means to determine if risk of collision exists. If in doubt, such risk shall be deemed to exist. Proper use shall be made of radar, including long-range scanning and systematic plotting; assumptions shall never be made on scanty information, especially scanty radar information. Risk shall be deemed to exist if the compass bearing of an approaching vessel does not appreciably change; risk may still exist even with an appreciable bearing change when approaching a very large vessel, a tow, or a vessel at close range.
These four rules form the assessment framework that sits underneath every encounter rule in Rules 11-18.
