Rule 19
(a)This Rule applies to vessels not in sight of one another when navigating in or near an area of restricted visibility.
(b) Every vessel shall proceed at a safe speed adapted to the prevailing circumstances and conditions of restricted visibility. A power-driven vessel shall have her engines ready for immediate maneuver.
(c) Every vessel shall have due regard to the prevailing circumstances and conditions of restricted visibility when complying with the Rules.
(d) A vessel which detects by radar alone the presence of another vessel shall determine if a close-quarters situation is developing and or risk of collision exists. If so, she shall take avoiding action in ample time, provided that when such action consists of an alteration in course, so far as possible the following shall be avoided:
(i) An alteration of course to port for a vessel forward of the beam, other than for a vessel being overtaken.
(ii) An alteration of course toward a vessel abeam or abaft the beam.
(e) Except where it has been determined that a risk of collision does not exist, every vessel which hears apparently forward of her beam the fog signal of another vessel, or which cannot avoid a close-quarters situation with another vessel forward of her beam, shall reduce her speed to be the minimum at which she can be kept on her course. She shall if necessary take all her way off and in any event navigate with extreme caution until danger of collision is over.
Comments Rule 19
Two considerations must first be met, the vessels must be in or near an area of restricted visibility, and they must not be in sight of each other. A vessel might be in clear weather, but near a fog bank, or might conceal another vessel, this Rule would then be applicable. The range of visibility is not specified, common sense should be used.
The requirement of Rules 19(b) and (e) for a safe speed goes back to Rule 6(a) with its specific conditions and requirement for stopping distance. The requirements of Rule 19(c) tie in with the provisions of Rule 5, Lookouts, Rule 7, Risk of Collision, and Rule 8, Action to Avoid Collision. If you have radar, Rule 19(d) should be read in used with Rule 6(b). Sound signals are required.
Rule 20 Application
(a) Rules in this part shall be complied with in all weathers.
(b)The Rules concerning lights shall be complied with from sunset to sunrise, and during such times no other lights shall be exhibited, except such lights which cannot be mistaken for the lights specified in these Rules or do not impair their visibility or distinctive character, or interfere with the keeping of a proper look-out.
(c)The lights prescribed by these Rules shall, if carried, also be exhibited from sunrise to sunset in restricted visibility and may be exhibited in all other circumstances when it is deemed necessary.
(d)The Rules concerning shapes shall be complied with by day.
Rule 20 Application, Lights and Shapes
(a) Rules in this Part shall be complied with in all weathers.
(b) The Rules concerning lights shall be complied with from sunset to sunrise, and during such times no other lights shall be exhibited, except such lights as cannot be mistaken for the lights specified in these Rules or do not impair their visibility or distinctive character, or interfere with the keeping of a proper lookout.
(c) The lights prescribed by these Rules shall, if carried, also be exhibited from sunrise to sunset in restricted visibility and may be exhibited in all other circumstances when it is deemed necessary.
(d) The Rules concerning shapes shall be complied with by day.
(e) The lights and shapes specified in these Rules shall comply with the provisions of Annex I of these Rules.
Comments Rule 20
For this Rule, "in all weathers" means the state of visibility, good or bad. Navigation lights may be shown at any time during the day. They must be shown in daytime if visibility is restricted and, of course, must be shown at night. "Dayshapes" are for daytime use only.
In order not to complicate the basic Navigation Rules, specifications for lights and shapes, and requirements for the placement of these on vessels, are given in Annex I.
Rule 21 Definitions
(a) "Masthead light" means a white light placed over the fore and aft centerline of the vessel showing an unbroken light over an arc of the horizon of 225 degrees and so fixed as to show the light from right ahead to 22.5 degrees abaft the beam on either side of the vessel, except that on a vessel of less than 12 meters in length the masthead light shall be placed as nearly as practicable to the fore and aft centerline of the vessel.
(b) "Sidelights" means a green light on the starboard side and a red light on the port side each showing an unbroken light over an arc of the horizon of 112.5 degrees and so fixed as to show the light from right ahead to 22.5 degrees abaft the beam on its respective side. In a vessel of less than 20 meters in length the sidelights may be combined in one lantern carried on the fore and aft centerline of the vessel, except that on a vessel of less than 12 meters in length the sidelights when combined in one lantern shall be placed as nearly as practicable to the fore and aft centerline of the vessel.
(c) "Sternlight" means a white light placed as nearly as practicable at the stern showing an unbroken light over an arc of the horizon of 135 degrees and so fixed as to show the light 67.5 degrees from right aft on each side of the vessel.
(d) "Towing light" means a yellow light having the same characteristics as the "sternlight" defined in paragraph (c) of this Rule.
(e) "All-round light" means a light showing an unbroken light over an arc of the horizon of 360 degrees.
(f) "Flashing light" means a light flashing at regular intervals at a frequency of 120 flashes or more per minute.
(g) "Special flashing light" means a yellow light flashing at regular intervals at a frequency of 50 to 70 flashes per minute, placed as far forward and as nearly as practicable on the fore and aft centerline of the tow and showing an unbroken light over an arc of the horizon of not less than 180 degrees nor more than 225 degrees and so fixed as to show the light from right ahead to abeam and no more than 22.5 degrees abaft the beam on either side of the vessel.
Comments Rule 21
The Inland Rules have less restrictive provisions for the masthead light and sidelights on vessels less than 12 meters (39.4 ft.) in length that do not appear in the International Rules.
The high rate of "flashing lights," 120 or more flashes per minute, is specified to prevent confusion with Quick-Flashing lights on aids to navigation, which flash at a nominal rate of 60 per minute.
The "special flashing light" is used in the Inland Rules only it is used to mark the forward end of a barge pushed ahead. Note that its arc of visibility can be slightly different from a masthead light, but is always not less than 180¼.
Rule 22 Visibility of Lights
The lights prescribed in these Rules shall have an intensity as specified in Annex 1 to these Rules, so as to be visible at the following minimum ranges:
(a) In a vessel of 50 meters or more in length:
a masthead light, 6 miles
a sidelight, 3 miles
a sternlight, 3 miles
a towing light, 3 miles
a white, red, green or yellow all-round light, 3 miles, and a special flashing light 2 miles
(b) In a vessel of 12 meters or more in length but less than 50 meters in length:
a masthead light, 5 miles, except where the length of the vessel is less than 20 meters, 3 miles.
a sidelight, 2 miles
a sternlight, 2 miles
a towing light, 2 miles
a white, red, green or yellow all-round light, 2 miles and, a special flashing light 2 miles.
(c) In a vessel of less than 12 meters in length:
a masthead light, 2 miles
a sidelight, 1 mile
a sternlight, 2 miles
a towing light, 2 miles
a white, red, green or yellow all-round light, 2 miles, and a special flashing light, 2 miles.
(d) In an inconspicuous, partly submerged vessel or object being towed: a white all-round light, 3 miles.
Comments Rule 22
The requirement of Rule 22 is the intensity of each navigation light, this is for the guidance of the manufacturers of the hardware. The stated ranges provide a necessary input into the formula used in Annex I to calculate the intensity. A light is "legal" if it meets the intensity requirement of Annex I, even though under some conditions of visibility it cannot be seen at the ranges stated in this Rule for that type of light. The stated ranges also provide guidelines for vessel operators and enforcement agencies in the field.
The Inland Rules state a visibility requirement of two miles for a "special flashing light", this light does not appear in the International Rules. This light is yellow, as is the light for air-cushion vessels when operating in the non-displacement mode, but the frequency of the flashes is different allowing an observer to differentiate between them.
