IALACOLREG
6

Safe Speed

Every vessel shall at all times proceed at a safe speed so that proper and effective action can be taken to avoid collision.

Rule 6 requires every vessel to proceed at a safe speed so that she can take proper and effective action to avoid collision and be stopped within a distance appropriate to the prevailing circumstances and conditions.

Factors for all vessels include:

a
the state of visibility (b) the traffic density, including concentrations of fishing vessels or any other vessels (c) the manoeuvrability of the vessel, especially stopping distance and turning ability (d) at night, the presence of background light such as shore lights or back scatter from the ship's own lights (e) the state of wind, sea and current, and the proximity of navigational hazards (f) the draught in relation to the available depth of water

Additional factors for vessels with operational radar include:

i
the characteristics, efficiency and limitations of the radar equipment
  • 1constraints imposed by the radar range scale in use
  • 2the effect of sea state, weather and interference on radar detection
  • 3the possibility that small vessels, ice and other floating objects may not be detected at an adequate range
  • 4the number, location and movement of vessels detected by radar
  • 5the more exact assessment of visibility that radar can provide when vessels or objects are detected nearby

STCW Bridge Watch Lens

1

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.

2

Build the traffic picture with sight, hearing, radar/ARPA and chart context. Do not let AIS or one isolated bearing replace systematic observation.

3

Safe speed is judged by what the ship can actually do in the moment: stop, turn, reduce exposure and avoid collision within the available sea room.

Exam Focus

1

Start every scenario by classifying the encounter: overtaking, head-on, crossing, narrow channel, traffic separation, or restricted visibility.

2

If two rules seem to conflict, check the order carefully: overtaking duties still apply, and Rule 2 still requires ordinary seamanship.

3

If schedule, fuel economy or comfort appears in the options, it is not a Rule 6 factor.

Key Takeaways

1

Safe speed is whatever allows timely, effective collision-avoidance action in the actual conditions

2

Stopping distance, turning ability and available sea room are part of the decision

3

Radar does not justify higher speed; it adds more factors that must be considered

4

Commercial pressure, schedule and convenience are never Rule 6 factors

Common Mistakes

Keeping too much speed in restricted visibility or dense traffic

Looking only at engine speed instead of the ship's actual stopping and turning performance

Assuming radar removes the need to slow down

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