COLREGs Rule 6: Safe speed for vessels
Last reviewed: October 14, 2026
Rule 6 requires every vessel to proceed at a safe speed at all times. A safe speed lets the vessel take proper and effective action to avoid collision and stop within a distance appropriate to the circumstances. The rule lists factors for all vessels and extra factors for vessels with operational radar.
Applies toEvery vessel, with additional factors for vessels with operational radar.
What it says
Every vessel must proceed at a safe speed at all times 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.
“Every vessel shall at all times proceed at a safe speed so that she can take proper and effective action to avoid collision”
In determining a safe speed, the listed factors must be among those taken into account.
“In determining a safe speed the following factors shall be among those taken into account:”
All vessels must take into account the state of visibility.
COLREGs Rule 6(a)(i)“the state of visibility;”
All vessels must take into account the maneuverability of the vessel, with special reference to stopping distance and turning ability in the prevailing conditions.
COLREGs Rule 6(a)(iii)“the maneuverability of the vessel with special reference to stopping distance and turning ability in the prevailing conditions;”
All vessels must take into account the draft in relation to the available depth of water.
COLREGs Rule 6(a)(vi)“the draft in relation to the available depth of water.”
Vessels with operational radar must also take into account the characteristics, efficiency and limitations of the radar equipment.
COLREGs Rule 6(b)(i)“the characteristics, efficiency and limitations of the radar equipment;”
Vessels with operational radar must also take into account the possibility that small vessels, ice and other floating objects may not be detected by radar at an adequate range.
COLREGs Rule 6(b)(iv)“the possibility that small vessels, ice and other floating objects may not be detected by radar at an adequate range;”
Common questions
When must a vessel proceed at a safe speed?
Every vessel must proceed at a safe speed at all times.
“Every vessel shall at all times proceed at a safe speed”
What factors must all vessels consider when determining safe speed at night?
At night, all vessels must take into account the presence of background light, such as from shore lights or from back scatter of her own lights.
“at night, the presence of background light such as from shore lights or from back scatter of her own lights;”
What extra factors apply to vessels with radar when setting safe speed?
Vessels with operational radar must additionally consider factors such as the radar range scale in use and the number, location and movement of vessels detected by radar.
“Additionally, by vessels with operational radar:”
The text of COLREGs Rule 6
U.S. Coast Guard, Navigation Rules and Regulations Handbook
Rule 6: Safe Speed
Every vessel shall at all times 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. In determining a safe speed the following factors shall be among those taken into account: (a) By all vessels: (i) the state of visibility; (ii) the traffic density including concentrations of fishing vessels or any other vessels; (iii) the maneuverability of the vessel with special reference to stopping distance and turning ability in the prevailing conditions; (iv) at night, the presence of background light such as from shore lights or from back scatter of her own lights; (v) the state of wind, sea and current, and the proximity of navigational hazards; (vi) the draft in relation to the available depth of water. (b) Additionally, by vessels with operational radar: (i) the characteristics, efficiency and limitations of the radar equipment; (ii) any constraints imposed by the radar range scale in use; (iii) the effect on radar detection of the sea state, weather and other sources of interference; (iv) the possibility that small vessels, ice and other floating objects may not be detected by radar at an adequate range; (v) the number, location and movement of vessels detected by radar; (vi) the more exact assessment of the visibility that may be possible when radar is used to determine the range of vessels or other objects in the vicinity.
The plain-English explanation on this page was written with AI from the regulation text above and checked automatically before publishing: every quote appears in the text, every number comes from it, and a second model confirmed each statement adds nothing the text doesn't say. Regulation text current as of August 12, 2024. The regulation text governs. RegKnot is not affiliated with the U.S. Coast Guard.