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

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Rule 23 -- Power-driven Vessels Underway


This Rule is the first of those Rules that describe the navigation light "picture" displayed by each vessel. Rule 23 covers power-driven vessels and gives the basic array of navigation lights--masthead light, sidelights, and sternlight--from which the arrays for other vessel types are derived.

You will note that significant differences exist between the International Rules and the Inland Rules with regard to navigation lights. The Inland Rules allow more optional displays and are less stringent in the positioning requirements. (These more relaxed provisions were often concessions to special-interest groups who wished to retain their traditional light configurations.)

Rule 23 applies to ordinary power-driven vessels of all sizes--from the recreational boat to the supertanker. It applies to power-driven fishing vessels when they are not engaged in fishing. It applies to tugboats assisting in ship maneuvering either not connected to the ship or connected with a short line or cable. It does not apply to power-driven vessels that are anchored, aground, or tied to a dock.


INTERNATIONAL

INLAND

(a) A power-driven vessel underway shall exhibit:

(i) a masthead light forward;

(ii) a second masthead light abaft of and higher than the forward one; except that a vessel of less than 50 meters in length shall not be obliged to exhibit such light but may do so;

(iii) sidelights;

(iv) a sternlight.

(a) A power-driven vessel underway shall exhibit:

(i) a masthead light forward;

(ii) a second masthead light abaft of and higher than the forward one; except that a vessel of less than 50 meters in length shall not be obliged to exhibit such light but may do so;

(iii) sidelights; and

(iv) a sternlight.

 

Paragraph (a) lists the navigation lights for ordinary power-driven vessels. Two masthead lights are required--one forward and one aft--except that small vessels only need one forward. The forward masthead light is placed in the forward half of the vessel, except that under Inland Rules this light does not have to be forward of amidships on small vessels. Sidelights and a sternlight are also required.

Details on the orientation and positioning of these navigation lights are in Rule 21 and in Annex I. Alternative navigation light configurations for vessels less than twelve meters in length are contained in paragraph (c).


INTERNATIONAL

INLAND

(b) An air-cushion vehicle when operating in the nondisplacement mode shall, in addition to the lights prescribed in paragraph (a) of this Rule, exhibit an all-round flashing yellow light.

(b) An air-cushion vehicle when operating in the nondisplacement mode shall, in addition to the lights prescribed in paragraph (a) of this Rule, exhibit an all-round flashing yellow light where it can best be seen.

 

Air-cushion vehicles are given a distinctive yellow flashing light in paragraph (b). The flashing (120 regular flashes per minute) all-round light is displayed only when the vessel is operating on its cushion of air. Air-cushion vehicles may operate at high speeds, may tend to travel a little sideways in a crosswind, and may not be able to turn quickly, depending on the design of the vessel.

A U.S. Navy regulation (Title 32 of the Code of Federal Regulations, section 707.7) permits the use of a flashing yellow light on submarines, but the flash characteristic is not the same. Also, submarines tend to be much quieter, do not generally travel sideways, and on occasion vanish.


INTERNATIONAL

INLAND

(c)(i) A power-driven vessel of less than 12 meters in length may in lieu of the lights prescribed in paragraph (a) of this Rule exhibit an all-round white light and sidelights;

(c) A power-driven vessel of less than 12 meters in length may in lieu of the lights prescribed in paragraph (a) of this Rule, exhibit an all-round white light and sidelights;

 

Some owners, operators, or builders of power-driven vessels under twelve meters in length feel that the conventional masthead light, sidelights, and sternlight array is too complicated, consumes too much power, or just costs too much. For them, paragraph (c) provides one or two alternatives.

Vessels less than twelve meters long may display an all-round white light and sidelights. The all-round white light is commonly mounted at the stern on the starboard side, but that location is a carry-over from superseded navigation rules. Under the current Rules, the all-round white light can be placed anywhere, so long as it is on a level at least one meter higher than the sidelights.

Putting the all-round light above the operator lessens interference with his or her night vision. In addition, carrying the all-round light in the forward part of the boat closer to the sidelights minimizes the decrease in vertical separation (all-round light / sidelights) when the boat assumes a bow-high trim (e.g. in the case of a planing boat traveling below planing speed).


INTERNATIONAL

(ii) a power-driven vessel of less than 7 meters in length whose maximum speed does not exceed 7 knots may in lieu of the lights prescribed in paragraph (a) of this Rule exhibit an all-round white light and shall, if practicable, also exhibit sidelights;

 

Under the International Rules, but not the Inland Rules, a power-driven vessel less than seven meters long may dispense with the sidelights, displaying only an all-round light, providing that its "maximum speed does not exceed seven knots." This means that its maximum speed during the time it is operating at night does not exceed seven knots.

One school of thought interprets "maximum speed does not exceed seven knots" to mean "maximum speed could not exceed seven knots" or "which is not capable of exceeding seven knots," but that is not what the Rule says. The Rule says "does not," present tense. If a single white light is safe for a five-knot boat going five knots, then it should also be safe for a twenty-five knot boat going five knots.


INTERNATIONAL

(iii) the masthead light or all-round white light on a power-driven vessel of less than 12 meters in length may be displaced from the fore and aft centerline of the vessel if centerline fitting is not practicable, provided that the sidelights are combined in one lantern which shall be carried on the fore and aft centerline of the vessel or located as nearly as practicable in the same fore and aft line as the masthead light or the all-round white light.

 

Both the International and Inland Rules allow for the off-centerline positioning of masthead or substitute all-round white light. The International Rule provision in Rule 23(c)(iii) is more restrictive than the Inland Rule provisions contained in Rule 21.


INLAND

(d) A power-driven vessel when operating on the Great Lakes may carry an all-round white light in lieu of the second masthead light and sternlight prescribed in paragraph (a) of this Rule. The light shall be carried in the position of the second masthead light and be visible at the same minimum range.

 

Paragraph (d) of Inland Rule 23 contains an alternative light configuration for Great Lakes vessels, in which an all-round white light replaces the after masthead light and sternlight. This provision is in the Rules not because the conditions or vessels on the Great Lakes are unique, but rather because when the Rules were rewritten, some Great Lakes mariners did not wish to give up their traditional navigation light arrangement.

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