Handbook of the Nautical Rules of the Road by Llana & Wisneskey

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Rule 21 -- Definitions


Rule 21 lists the types of navigation lights making up the various arrays specified in Rules 23 to 31. There are no other types of navigation lights and each one has only one name. Other navigation light terms, such as "steaming light" or "bow light" are from popular slang or from old rules no longer in effect.


INTERNATIONAL

INLAND

(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.

(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.

 

The masthead light is used in a number of ways but always has the same characteristics and orientation. It points forward and is normally the highest navigation light on the vessel. There may be only one masthead light (on smaller vessels), or two may be carried -- one on a forward mast and another further aft and higher on another mast. Two or three may be carried in a vertical line on a single mast (for towing) with perhaps another single masthead light carried on another mast.

On sailing vessels, on rowboats, and with some optional lighting configurations on smaller power-driven vessels, there may be no masthead light at all.

The Inland Rule definition of masthead light permits it to be mounted on one side on small vessels, while a similar provision in Rule 23 of the International Rules permits the same offset for power-driven vessels only. Otherwise, the light must be placed on the centerline.


INTERNATIONAL

INLAND

(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.

(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.

 

Sidelights are the green and red lights mounted on either side of a vessel. If you are a power-driven vessel and see another power-driven vessel (recognized by its "picture" of navigation lights) with its green light showing, then your vessel is the stand-on vessel and you should hold your course and speed. If you see the red light, then you should stay out of the way.

Under the Inland Rules, combined sidelights on small vessels may be mounted off the centerline. (A comparable International Rule provision for power-driven vessels only is in Rule 23.) Otherwise the International and Inland sidelights are the same.


INTERNATIONAL

INLAND

(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.

(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.

 

The sternlight is pointed directly aft and is normally mounted right on the very stern, often on the centerline. It does not have to be on the centerline and it does not have to be at the stern, but "as nearly as practicable" at the stern. It is not unusual for it to be quite some distance from the stern on vessels where the stern is perhaps low and exposed to rough use, as on a stern trawler or an offshore oil-platform supply vessel.


INTERNATIONAL

INLAND

(d) "Towing light" means a yellow light having the same characteristics as the "sternlight" defined in paragraph (c) of this Rule.

(d) "Towing light" means a yellow light having the same characteristics as the "sternlight" defined in paragraph (c) of this Rule.

 

Towing lights may be used either with or without stern lights, depending on whether you are using the International or Inland Rules.


INTERNATIONAL

INLAND

(e) "All-round light" means a light showing an unbroken light over an arc of 360 degrees.

(e) "All-round light" means a light showing an unbroken light over an arc of 360 degrees.

 

All-round lights have many applications and come in red, green, yellow, and white.


INTERNATIONAL

INLAND

(f) "Flashing light" means a light flashing at regular intervals at a frequency of 120 flashes or more per minute.

(f) "Flashing light" means a light flashing at regular intervals at a frequency of 120 flashes or more per minute.

 

A flashing light is used only on air-cushion vehicles and is yellow. The flash charcteristic was chosen to distinguish the light from the slower flashing of many lighted aids to navigation (buoys and markers).


INLAND

(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.

 

The special flashing light is also yellow but exists only in the Inland Rules. It is used at the head of barges being pushed ahead.

The light can have the 225-degree horizontal arc characteristic of a masthead light or anything down to 180 degrees. If a 225-degree light is mounted on top of the front of a barge, it could be seen through the full 225-degree arc, but if mounted on the front face of the barge, it would only be seen through a 180-degree horizontal arc. The flexibility in the requirement permits different light construction and mounting techniques.

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Rule 22