Which three factors are used to determine safe speed under COLREGS Rule 6?

• A. Vessel color, hull length, engine power.
• B. Distance to port, time of day, wind direction.
• C. Visibility, traffic density, weather/sea state.
• D. Water depth, tide, star visibility.

Answer: (C)

Safe speed is about setting a speed you can use to take proper and effective action to avoid a collision under the prevailing conditions. Three factors to guide that speed are visibility, traffic density, and the weather/sea state.

Visibility matters because what you can see sets how far you can detect other vessels and obstacles. In fog, heavy rain, or darkness, you must slow so you can observe in time to react and stop if needed.

Traffic density describes how crowded the area is with other vessels. In busy waterways, you need to slow to give yourself room to maneuver and to anticipate others’ actions, reducing the chance of meeting a vessel unexpectedly.

Weather and sea state affect how well your vessel handles and how quickly you can stop. Gusty winds, high seas, or strong currents change stopping distance and maneuverability, so safer speeds are lower to maintain control and prevent collisions.

Other factors like hull length, engine power, or time of day aren’t the primary determinants for safe speed in this rule. They influence performance, but the decision about safe speed centers on visibility, traffic, and weather/sea conditions.