Boating in Restricted Visibility … The term “restricted visibility” is defined in the Navigation Rules as any condition in which visibility is restricted by fog, mist, falling snow, heavy rainstorms, sandstorms, or any other similar causes. While not specifically mentioned in the rules, visibility is impaired as the sun sets and the darkness of night arrives. In addition, the presence of bright lights on land at night can further restrict visibility. The toughest time of all is when poor weather conditions exist at night! When operating a boat in an area where visibility is restricted, the best thing to do is slow down and maintain a sharp lookout; using eyes, ears, and any electronic aids available.
When a ship’s crew encounters restricted visibility, the rules state that a vessel shall at all times proceed at a safe speed. However, the rules do not include a firm definition of what a safe speed is. Many mariners define it as being able to stop within a specified distance, which is not correct. The rules state that a safe speed is one at which a vessel can take proper and effective action to avoid collision, and be stopped within a distance appropriate to the prevailing circumstances and conditions. So, a safe speed during a rain storm in the middle of the afternoon is far different than a safe speed on a foggy night in heavy seas during a thunder storm. The key point is to respect the weather and respect the fact that the faster the boat is traveling when visibility is restricted the higher the risks become.
In addition to addressing a vessel’s speed, the rules further define the expected conduct of vessels operating within an area where visibility is restricted. For example; if onboard, the Radar unit must be turned on and monitored at all times. Also, if you are on a power driven vessel you must keep your engines ready for immediate maneuvering if required. Lastly, any vessel which hears the sound of another vessel’s fog signal directly ahead shall reduce speed to the minimum at which she can keep on course and navigate with caution until the danger of collision is over.
Fog signals are audio and visual aids that help skippers determine what types of vessels, or other obstructions are within the area where visibility is restricted. For instance, sound or light signals emitted by a lighthouse or buoy can be heard or seen in restricted visibility. Such signals can indicate shorelines, channels, rocks or other dangerous stretches of water. Each signal has a distinctive code transmitted via flashing lights, and the sounding of gongs, bells, or horns. These signals are all identified on charts of the area, which is one reason why it is advisable to have charts of your local area, and charts covering the area of any cruise you may have planned onboard before you leave port.
All vessels, whether stationary or moving, are required by law to utilize fog signals in inclement weather. The length, and timing of each signal helps to generally identify different types of vessels. Fog signals can also help indicate an approaching vessel’s position by listening for the direction from which the sound is emanating. In addition, identifying louder or softer volumes can indicate if a vessel is getting closer or moving further away.
Modern ships’ radios that are equipped with a loud hailer are preprogramed to automatically sound the appropriate
fog signals for specific types of vessels. Most fog signals consist of a combination of short (1 second) and prolonged (4-6 second) horn blasts sounded once every two minutes. For example, a power driven vessel making way sounds one prolonged blast. If underway but stopped a power driven vessel sounds two prolonged blasts.
Following power boats there is a large category of vessels that should be respected and given extra space to maneuver. These are defined as vessels not under command, restricted in ability to maneuver, constrained by draft, sailing, fishing, towing astern or pushing ahead, and restricted at anchor. All are indicated by one prolonged followed by two short horn blasts. If you hear such a signal slow down, keep a sharp lookout, and leave plenty of room.
In addition to the above, a manned tow sounds one prolonged followed by three short blasts; a pilot vessel sounds four short blasts, and any vessel at anchor has the option of sounding one short-one prolonged-one short blasts.Vessels anchored or aground sound bells and gongs. An anchored vessel less than 100 meters long rings its bell rapidly for 5 seconds every minute. If longer than 100 meters, a vessel sounds its bell for 5 seconds followed by a sounding of its gong for another 5 seconds . If aground, a vessel sounds 3 bell claps followed by a rapid ringing of the bell for 5 seconds, ended by 3 more bell claps. If longer than 100 meters add a 5 second rapid sounding of the gong.