Restricted visibility poses a significant challenge for navigation, as it increases the risk of collision, grounding, or stranding. Therefore, it is essential for you to determine a safe speed in restricted visibility, which allows you to take appropriate action to avoid any danger. Restricted visibility is a condition where the visibility of the surroundings is reduced due to fog, mist, rain, snow, smoke, or darkness.
Safe Speed in Restricted Visibility
According to the Rule 6: Safe speed of the International Regulations for Preventing Collisions at Sea (COLREGS), every vessel must proceed at a safe speed at all times, and especially in restricted visibility. A safe speed is one that enables the vessel to stop within a distance appropriate to the prevailing circumstances and conditions. However, there is no fixed formula or rule to calculate a safe speed, as it depends on various factors, such as:
– The type, size, and maneuverability of your vessel
– The traffic density and the proximity of other vessels
– The presence of navigational hazards, such as shoals, rocks, or wrecks
– The weather and sea conditions, such as wind, waves, and currents
– The availability and reliability of navigational aids, such as radar, GPS, or AIS
– The experience and competence of the crew and the master
Therefore, determining a safe speed in restricted visibility requires a careful assessment of all these factors, and a constant monitoring of the situation. The OOW must consider the use of ‘ship radar’.
Radar: A ray of light for OOW
A ‘ship radar‘ is a device that uses radio waves to detect and track objects in the surrounding area. Hence the condition of fog will have the very least effect on the working of a radar. It helps maneuvering a ship in restricted visibility by providing information such as the range, bearing, speed, and course of other vessels, as well as the location of landmasses, buoys, and other navigational aids. A ship radar can also assist in collision avoidance and path planning by displaying the closest point of approach (CPA) and the time to CPA (TCPA) of any potential targets.
To use a ship radar effectively, the officer of the watch (OOW) must follow the International Regulations for the Prevention of Collisions at Sea (COLREGS), especially Part B (Steering and Sailing Rules) Section III (Rule 19) – Conduct of vessels in restricted visibility and Section I (Rules 4 to 10 inclusive) – Conduct of vessels in any condition of visibility. The OOW must also adjust the radar settings properly, such as the range scale, the gain, the sea and rain clutter, and the electronic bearing line (EBL) and variable range marker (VRM). Moreover, the OOW must keep a proper lookout, summon help to the bridge, and proceed at a safe speed adapted to the prevailing circumstances.
Conclusion
There is no fixed value or formulae for the safe speed of a vessel in restricted visibility. However, the competence, knowledge and understanding of the OOW and a judicious use of the ‘ship radar’ have always proven to be the best friends of an OOW in such situations. In case the OOW is still unsure of the course of actions he should take or is in any doubt, he must immediately call Master on the bridge.
