An Act to authorize the President to proclaim regulations for preventing collisions at sea
PL 82-172 (H.R.5013), enacted 10/11/1951

406 
PUBLIC LAW 172—OCT. 11, 1951 
[65 STAT 
Acquisition of lands, 
etc. 
Use of Colorado 
River water. 
Condition and cove-
nant. 
Provision for con-
struction. 
Appropriation au-
thorized. 
46 S t a t . , P t . 2, 
p. 3000. 
45 Stat. 1057. 
43 U. S. C. § 617t. 
than that charged other users of comparable quantities of water, 
a quantity of water sufficient to meet the requirements of Govern-
ment activities located and to be located in the area served by such 
agencies. 
SEC. 4. For the purpose of enabling him to carry out the provisions 
of the first section of this Act, the Secretary of the Navy is author-
ized to acquire lands and rights pertaining thereto, or other interests 
therein, including the temporary use thereof, by donation, purchase, 
exchange of Government-owned lands, or otherwise. 
SEC. 5. The United States and the San Diego County Water 
Authority and their respective permittees, licensees, and contractees 
and all users and appropriators of water of the Colorado River 
diverted or delivered through the existing aqueduct and the enlarge-
ment or addition thereto shall observe and be subject to the Colorado 
River Compact, the Boulder Canyon Project Act, the California Self-
Limitation Statute and the Mexican Water Treaty in the diversion, 
delivery, and use of water of the Colorado River, anything in this 
Act to the contrary notwithstanding, and such condition and cove-
nant shall attach as a matter of law whether or not set out or referred 
to in the instrument evidencing such permit, license, or contract and 
shall be deemed to be for the benefit of and be available to the States 
of Arizona, California, Colorado, Nevada, New Mexico, Utah, and 
Wyoming and the users of water therein or thereunder by way of suit, 
defense, or otherwise in any litigation respecting the waters of the 
Colorado River. 
SEC. 6. The Secretary of the Navy is authorized to provide for the 
construction of the whole or any part of the work authorized by the 
first section of this Act (1) by contract, (2) by the use of facilities 
and personnel of the Navy Department, or (3) by the use of the 
facilities and personnel of any other department or agency of the 
United States with which an agreement may be entered into to per-
form or to have performed the whole or any part of such work. 
SEC. 7. The appropriation of such sums as may be necessary to 
carry out the provisions of this Act is hereby authorized. 
SEC. 8. This Act and all works constructed hereunder shall be sub-
ject to and controlled by the Colorado River Compact dated November 
24, 1922, and proclaimed effective by the President June 25, 1929; 
the Boulder Canyon Project Act approved December 21, 1928; the 
California Limitation Act approved by the Governor of California 
March 4,1929; and no right or claim of right to the use of the waters 
of the Colorado River shall be aided or prejudiced hereby. 
Approved October 11, 1951. 
October 11,1951 
[H. R. 5013] 
Public Law 172 
CHAPTER 495 
AN ACT 
To authorize the President to proclaim regulations for preventing collisions 
at sea. 
Regulations for pre-
venting collisions at 
Publication. 
Be it enacted hy the Senate and House of Representatives 
of the 
United States of America in Congress assembled^ That the President 
is authorized to proclaim the regulations set forth in section 6 of this 
Act for preventing collisions involving water-borne craft upon the 
high seas, and in all waters connected therewith. 
Such proclamation, 
together with the regulations, shall be published in the Federal 
65 STAT. 
PUBLIC LAW 172—OCT. 11, 1961 
407 
Register, and, after the effective date specified in such proclamation, 
such regulations shall have effect as if enacted by statute and shall 
be followed by all public and private vessels of the United States, and 
by all aircraft of United States registry to the extent therein made 
applicable. 
Such regulations shall not apply to the harbors, rivers, 
and inland waters of the United States; to the Great Lakes of North 
America and their connecting and tributary waters as far east as the 
lower exit of the Lachine Canal in Montreal in the Province of 
Quebec, Canada; to the Red River of the North and the rivers empty-
ing into the Gulf of Mexico and their tributaries; nor, with respect to 
aircraft, to any territorial waters of the United States. 
SEC. 2. Any requirements of such regulations in respect of the num-
ber, position, range of visibility, or arc of visibility of the lights 
required to be displayed by vessels shall not apply to any vessel of the 
Navy or of the Coast Guard whenever the Secretary of the Navy or 
the Secretary of the Treasury, in the case of Coast Guard vessels 
operating under the Treasury Department, or such official as either 
may designate, shall find or certify that, by reason of special construc-
tion, it is not possible for such vessel or class of vessels to comply with 
such regulations. The lights of any such exempted vessel or class of 
vessels, however, shall conform as closely to the lequirements of the 
applicable regulations as the Secretary or such official shall find or 
certify to be feasible. Notice of such findings or certification and of 
the character and position of the lights prescribed to be displayed on 
such exempted vessel or class of vessels shall be published in the 
Federal Register and in the Notice to Mariners and, after the effective 
date specified in such notice, shall have effect as part of such 
regulations. 
SEC. 3. Section 7 (a) of the Air Commerce Act of 1926 (U. S. C, 
1946 edition, title 49, sec. 177 (a)), is amended to read as follows: 
"Except as specifically provided in the Act entitled 'An Act to 
authorize the President to proclaim regulations for preventing col-
lisions at sea', the navigation and shipping laws of the United States, 
including any definition of 'vessel' or 'vehicle' found therein and 
including the rules for the prevention of collisions, shall not be con-
strued to apply to seaplanes or other aircraft or to the navigation of 
vessels in relation to seaplanes or other aircraft." 
&SC. 4. Section 610 (a) of the Civil Aeronautics Act of 1938 
(U. S. C , 1946 edition, title 49, sec. 560 (a)), is amended by deleting 
the word "and" at the end of paragraph (4) ; by changing the period 
at the end of paragraph (5) to a semicolon and adding the word "and"; 
and by adding a new paragraph (6) reading as follows: 
"(6) For any person to operate a seaplane or other aircraft of 
United States registry upon the high seas in contravention of the 
regulations proclaimed by the President pursuant to section 1 of the 
Act entitled 'An Act to authorize the President to proclaim regula-
tions for preventing collisions at sea'." 
S E C 5. After such regulations proclaimed under section 1 hereof 
shall have taken effect, all statutes, regulations, and rules in conflict 
therewith shall be of no further force and effect. Until such time as 
such regulations shall have been proclaimed and made effective pur-
suant to this Act, nothing herein shall in any way limit, supersede, 
or repeal any regulations for the prevention of collisions, which have 
heretofore been prescribed by statute, regulation, or rule. 
Nonapplicability. 
Lights displayed by 
vessels. 
Exemptions. 
Publication of find-
ings, etc. 
44 Stat. 572. 
Nonapplicability to 
aircraft. 
52 Stat. 1012. 
Conflicting statutes,, 
etc. 
408 
PUBLIC LAW 172—OCT. 11, 1951 
[65 STAT. 
venttog^couisiorif'at 
^EC. 6. T h e regulations authorized to be proclaimed under sec-
sea, 1948. 
tion 1 hereof are the Regulations for Preventing Collisions at Sea, 
1948, approved by the International Conference on Safety of Life at 
Sea, 1948, held at London from April 23 to June 10, 1948, as follows: 
PART A.—PRELIMINARY AND DEFINITIONS 
RULE 1 
(a) These Rules shall be followed by all vessels and seaplanes upon 
the high seas and in all waters connected therewith navigable by 
seagoing vessels, except as provided in Rule 30. Where, as a result 
of their special construction, it is not possible for seaplanes to comply 
fully with the provisions of Rules specifying the carrying of lights 
and shapes, these provisions shall be followed as closely as circum-
stances permit. 
(b) The Rules concerning lights shall be complied with in all 
weathers from sunset to sunrise, and during such times no other 
lights shall be exhibited, except such lights as cannot be mistaken for 
the prescribed lights or impair their visibility or distinctive character, 
or interfere with the keeping of a proper look-out, 
(c) In the following Rules, except where the context otherwise 
requires:— 
(i) the word "vessel" includes every description of water craft, 
other than a seaplane on the water, used or capable of being used 
as a means of transportation on water; 
(ii) the word "seaplane" includes a flying boat and any other 
aircraft designed to manoeuvre on the water; 
(iii) the term "power-driven vessel" means any vessel propelled 
by machinery; 
(iv) every power-driven vessel which is under sail and not 
under power is to be considered a sailing vessel, and every vessel 
under power, whether under sail or not, is to be considered a 
power-driven vessel; 
(v) a vessel or seaplane on the water is "under way" when she 
is not at anchor, or made fast to the shore, or aground; 
(vi) the term "height above the hull" means height above the 
uppermost continuous deck; 
(vii) the length and breadth of a vessel shall be deemed to be 
the length and breadth appearing in her certificate of registry; 
(viii) the length and span of a seaplane shall be its maximum 
length and span as shown in its certificate of airworthiness, or as 
determined by measurement in the absence of such certificate; 
(ix) the word "visible," when applied to lights, means visible 
on a dark night with a clear atmosphere; 
(x) the term "short blast" means a blast of about one second's 
duration; 
(xi) the term "prolonged blast" means a blast of from four 
to six seconds' duration; 
(xii) the word "whistle" means whistle or siren; 
(xiii) the word "tons" means gross tons. 
PART B.—LIGHTS AND SHAPES 
RULE 2 
(a) A power-driven vessel when under way shall carry:— 
(i) On or in front of the foremast, or if a vessel without a 
foremast then in the forepart of the vessel, a bright white light 
65 STAT.] 
PUBLIC LAW 172—OCT. 11, 1951 
409 
so constructed as to show an unbroken light over an arc of the 
horizon of 20 points of the compass (225 degrees), so fixed as to 
show the light 10 points (112% degrees) on each side of the 
vessel, that is, from right ahead to 2 points (22% degrees) abaft 
the beam on either side, and of such a character as to be visible 
at a distance of at least 5 miles. 
(ii) Either forward of or abaft the white light mentioned in 
sub-section (i) a second white light similar in construction and 
character to that light. 
Vessels of less than 150 feet in length, 
and vessels engaged in towing, shall not be required to carry this 
second white light but maj^ do so. 
(iii) These two white lights shall be so placed in a line with 
and over the keel that one shall be at least 15 feet higher than 
the other and in such a position that the lower light shall be for-
ward of the upper one. The horizontal distance between the two 
white lights shall be at least three times the vertical distance. 
The lower of these two white lights or, if only one is carried, then 
that light, shall be placed at a height above the hull of not less 
than 20 feet, and, if the breadth of the vessel exceeds 20 feet, then 
at a height above the hull not less than such breadth, so however 
that the light need not be placed at a greater height above the 
hull than 40 feet. 
In all circumstances the light or lights, as the 
case may be, shall be so placed as to be clear of and above all 
other lights and obstructing superstructures. 
(iv) On the starboard side a green light so constructed as to 
show an unbroken light over an arc of the horizon of 10 points of 
the compass (1121/2 degrees), so fixed as to show the light from 
right ahead to 2 points (22% degrees) abaft the beam on the star-
board side, and of such a character as to be visible at a distance of 
at least 2 miles. 
(v) On the port side a red light so constructed as to show an 
unbroken light over an arc of the horizon of 10 points of the com-
pass (112% degrees), so fixed as to show the light from right 
ahead to 2 points (22% degrees) abaft the beam on the port side, 
and of such a character as to be visible at a distance of at least 2 
miles. 
(vi) The said green and red sidelights shall be fitted with 
inboard screens projecting at least 3 feet forward from the light, 
so as to prevent these lights from being seen across the bows, 
(b) A seaplane under way on the water shall carry:— 
(i) In the forepart amidships where it can best be seen a bright 
white light, so constructed as to show an unbroken light over an 
arc of the horizon of 220 degrees of the compass, so fixed as to show 
the light 110 degrees on each side of the seaplane, namely, from 
right ahead to 20 degrees abaft the beam on either side, and of 
such a character as to be visible at a distance of at least 3 miles. 
(ii) On the right or starboard wing tip a green light, so con-
structed as to show an unbroken light over an arc of the horizon 
of 110 degrees of the compass, so fixed as to show the light from 
right ahead to 20 degrees abaft the beam on the starboard side, 
and of such a character as to be visible at a distance of at least 
2 miles. 
(iii) On the left or port wing tip a red light, so constructed 
as to show an unbroken light over an arc of the horizon of 110 
degrees of the compass, so fixed as to show the light from right 
ahead to 20 degrees abaft the beam on the port side, and of such 
a character as to be visible at a distance of at least 2 miles. 
410 
PUBLIC LAW 172—OCT. 11, 1951 
[65 STAT. 
•-.•!;• -i 
R U L E 
3 
(a) A power-driven vessel when towing or pushing another vessel 
or seaplane shall, in addition to her sidelights, carry two bright white 
lights in a vertical line one over the other, not less than 6 feet apart, 
and when towing more than one vessel shall carry an additional bright 
white light 6 feet above or below such lights, if the length of the tow, 
measuring from the stern of the towing vessel to the stern of the last 
vessel or seaplane towed, exceeds 600 feet. 
Each of these lights shall 
be of the same construction and character and one of them shall be 
carried in the same position as the white light mentioned in Rule 2 
(a) (i), except the additional light, which shall be carried at a height 
of not less than 14 feet above the hull. 
In a vessel with a single mast, 
such lights may be carried on the mast. 
(b) The towing vessel shall also show either the stern light specified 
in Rule 10 or in lieu of that light a small white light abaft the funnel 
or aftermast for the tow to steer by, but such light shall not be visible 
forward of the beam. 
The carriage of the white light specified in 
Rule 2 (a) (ii) is optional. 
(c) A seaplane on the water, when towing one or more seaplanes 
or vessels, shall carry the lights prescribed in Rule 2 (b) (i), (ii) 
and (iii); and, in addition, she shall carry a second white light of 
the same construction and character as the white light mentioned in 
Rule 2 (b) (i), and in a vertical line at least 6 feet above or below such 
light. 
RULE 
4 
(a) A vessel which is not under command shall carry, where they 
can best be seen, and, if a power-driven vessel, in lieu of the lights 
required by Rule 2 (a) (i) and (ii), two red lights in a vertical line 
one over the other not less than 6 feet apart, and of such a character as 
to be visible all round the horizon at a distance of at least 2 miles. 
By day, she shall carry in a vertical line one over the other not less than 
6 feet apart, where they can best be seen, two black balls or shapes 
each not less than 2 feet in diameter. 
(b) A seaplane on the water which is not under command may carry, 
where they can best be seen, two red lights in a vertical line, one over 
the other, not less than 3 feet apart, and of such a character as to be 
visible all round the horizon at a distance of at least 2 miles, and may 
by day carry in a vertical line one over the other not less than 3 feet 
apart, where they can best be seen, two black balls or shapes, each not 
less than 2 feet in diameter. 
(c) A vessel engaged in laying or in picking up a submarine cable 
or navigation mark, or a vessel engaged in surveying or underwater 
operations when from the nature of her work she is unable to get out 
of the way of approaching vessels, shall carry, in lieu of the lights 
specified in Rule 2 (a) (i) and (ii), three lights in a vertical line one 
over the other not less than 6 feet apart. The highest and lowest of 
these lights shall be red, and the middle light shall be white, and 
they shall be of such a character as to be visible all round the horizon 
at a distance of at least 2 miles. By day, she shall carry in a vertical 
line one over the other not less than 6 feet apart, where they can best 
be seen, three shapes each not less than 2 feet in diameter, of which 
the highest and lowest shall be globular in shape and red in colour, 
and the middle one diamond in shape and white. 
(d) The vessels and seaplanes referred to in this Rule, when not 
making way through the water, shall not carry the coloured sidelights, 
but when making way they shall carry them. 
65 STAT.] 
PUBLIC LAW 172—OCT. 11, 1951 
411 
(e) The lights and shapes required to be shown by this Rule are 
to be taken by other vessels and seaplanes as signals that the vessel or 
seaplane showing them is not under command and cannot therefore 
get out of the way. 
(f) These signals are not signals of vessels in distress and requiring 
assistance. Such signals are contained in Rule 31. 
RULE 5 
(a) A sailing vessel under way and any vessel or seaplane being 
towed shall carry the same lights as are prescribed by Rule 2 for a 
power-driven vessel or a seaplane under way, respectively, with the 
exception of the white lights specified therein, which they shall never 
carry. They shall also carry stern lights as specified in Rule 10, pro-
vided that vessels towed, except the last vessel of a tow, may carry, 
in lieu of such stern light, a small white light as specified in Rule 
3 ( b ) . 
(b) A vessel being pushed ahead shall carry, at the forward end, 
on the starboard side a green light and on the port side a red light, 
which shall have the same characteristics as the lights described in 
Rule 2 (a) (iv) and (v) and shall be screened as provided in Rule 2 
(a) (vi), provided that any number of vessels pushed ahead in a group 
shall be lighted as one vessel. 
RULE 6 
(a) In small vessels, when it is not possible on account of bad 
weather or other sufficient cause to fix the green and red sidelights, 
these lights shall be kept at hand lighted and ready for immediate use, 
and shall, on the approach of or to other vessels, be exhibited on their 
respective sides in sufficient time to prevent collision, in such manner 
as to make them most visible, and so that the green light shall not be 
seen on the port side nor the red light on the starboard side, nor, if 
practicable, more than 2 points ( 2 2 ^ degrees) abaft the beam on their 
respective sides. 
(b) To make the use of these portable lights more certain and 
easy, the lanterns containing them shall each be painted outside with 
the colour of the lights they respectively contain, and shall be provided 
with proper screens. 
RULE 7 
Power-driven vessels of less than 40 tons, vessels under oars or 
sails of less than 20 tons, and rowing boats, when under way shall not 
be required to carry the lights mentioned in Rule 2, but if they do 
not carry them they shall be provided with the following lights:— 
(a) Power-driven vessels of less than 40 tons, except as provided 
in section (b), shall carry:— 
(i) In the forepart of the vessel, where it can best be seen, and 
at a height above the gunwale of not less than 9 feet, a bright 
white light constructed and fixed as prescribed in Rule 2 (a) (i) 
and of such a character as to be visible at a distance of at least 
3 miles. 
(ii) Green and red sidelights constructed and fixed as pre-
scribed in Rule 2 (a) (iv) and (v), and of such a character as 
to be visible at a distance of at least 1 mile, or a combined lantern 
showing a green light and a red light from right ahead to 2 
points (221^ degrees) abaft the beam on their respective sides. 
Such lantern shall be carried not less than 3 feet below the white 
light. 
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PUBLIC LAW 172—OCT. 11, 1951 
[65 STAT. 
(b) Small power-driven boats, such as are carried by seagoing 
vessels, may carry the white light at a less height than 9 feet above 
the gunwale, but it shall be carried above the sidelights or the combined 
lantern mentioned in subsection (a) (ii). 
(c) Vessels of less than 20 tons, under oars or sails, except as pro-
vided in section (d), shall, if they do not carry the sidelights, carry 
where it can best be seen a lantern showing a green light on one side 
and a red light on the other, of such a character as to be visible at a 
distance of at least 1 mile, and so fixed that the green light shall not 
be seen on the port side, nor the red light on the starboard side. Where 
it is not possible to fix this light, it shall be kept ready for immediate 
use and shall be exhibited in sufficient time to prevent collision and 
so that the green light shall not be seen on the port side nor the red 
light on the starboard side. 
(d) Small rowing boats, whether under oars or sail, shall only be 
required to have ready at hand an electric torch or a lighted lantern 
showing a white light which shall be exhibited in sufficient time to 
prevent collision. 
(e) The vessels and boats referred to in this Rule shall not be re-
quired to carry the lights or shapes prescribed in Rules 4 (a) and 
11 (e). 
RULE 8 
(a) (i) Sailing pilot-vessels, when engaged on their station on 
pilotage duty and not at anchor, shall not show the lights prescribed 
for other vessels, but shall carry a white light at the masthead visible 
all round the horizon at a distance of at least 3 miles, and shall also 
exhibit a flare-up light or flare-up lights at short intervals, which 
shall never exceed 10 minutes. 
(ii) On the near approach of or to other vessels they shall have 
their sidelights lighted ready for use and shall flash or show them 
at short intervals, to indicate the direction in which they are heading, 
but the green light shall not be shown on the port side, nor the red 
light on the starboard side. 
(iii) A sailing pilot-vessel of such a class as to be obliged to go 
alongside of a vessel to put a pilot on board may show the white light 
instead of carrying it at the masthead and may, instead of the side-
lights above mentioned, have at hand ready for use a lantern with a 
green glass on the one side and a red glass on the other to be used as 
prescribed above. 
(b) A power-driven pilot-vessel when engaged on her station on 
pilotage duty and not at anchor shall, in addition to the lights and 
flares required for sailing pilot-vessels, carry at a distance of 8 feet 
below her white masthead light a red light visible all around the 
horizon at a distance of at least 3 miles, and also the sidelights required 
to be carried by vessels when under way. 
A bright intermittent all 
round white light may be used in place of a flare. 
(c) All pilot-vessels, when engaged on their stations on pilotage 
duty and at anchor, shall carry the lights and show the flares prescribed 
in sections (a) and (b), except that the sidelights shall not be showm. 
They shall also carry the anchor light or lights prescribed in Rule 11. 
(d) All pilot-vessels, whether at anchor or not at anchor, shall, 
when not engaged on their stations on pilotage duty, carry the same 
lights as other vessels of their class and tonnage. 
RULE 9 
(a) Fishing vessels when not fishing shall show the lights or shapes 
prescribed for similar vessels of their tonnage. When fishing they 
shall show only the lights or shapes prescribed by this Rule, which 
65 STAT.] 
PUBLIC LAW 172—OCT. 11, 1951 
413 
lights or shapes, except as otherwise provided, shall be visible at a 
distance of at least 2 miles* 
(b) Vessels fishing with trolling (towing) lines, shall show only 
the lights prescribed for a power-driven or sailing vessel under way 
as may be appropriate. 
(c) Vessels fishing with nets or lines, except trolling (towing) 
lines, extending from the vessel not more than 500 feet horizontally 
into the seaway shall show, where it can best be seen, one all round 
white light and in addition, on approaching or being approached by 
another vessel, shall show a second white light at least 6 feet below 
the first light and at a horizontal distance of at least 10 feet away 
from it (6 feet in small open boats) in the direction in which the out-
lying gear is attached. By day such vessels shall indicate their occu-
pation by displaying a Basket where it can best be seen; and if they 
have their gear out while at anchor, they shall, on the approach of 
other vessels, show the same signal in the direction from the anchor 
ball towards the net or gear. 
(d) Vessels fishing with nets or lines, except trolling (towing) 
lines, extending from the vessel more than 500 feet horizontally 
into the seaway shall show, where they can best be seen, three white 
lights at least 3 feet apart in a vertical triangle visible all around 
the horizon. When making way through the water, such vessels shall 
show the proper coloured sidelights but when not making way they 
shall not show them. By day they shall show a basket in the forepart 
of the vessel as near the stem as possible not less than 10 feet above 
the rail; and, in addition, where it can best be seen, one black conical 
shape, apex upwards. If they have their gear out while at anchor 
they shall, on the approach of other vessels, show the basket in the 
direction from the anchor ball towards the net or gear. 
(e) Vessels when engaged in traveling, by which is meant the 
dragging of a dredge net or other apparatus along or near the bottom 
of the sea, and not at anchor:— 
(i) If power-driven vessels, shall carry in the same position 
as the white light mentioned in Rule 2 (a) (i) a tri-coloured 
lantern, so constructed and fixed as to show a white light from 
right ahead to 2 points (221/2 degrees) on each bow, and a green 
light and a red light over an arc of the horizon from 2 points 
(221/2 degrees) on each bow to 2 points (221/^ degrees) abaft the 
beam on the starboard and port sides, respectively; and not less 
than 6 nor more than 12 feet below the tri-coloured lantern a Avhite 
light in a lantern, so constructed as to show a clear, uniforjn, 
and unbroken light all round the horizon. They shall also show 
the stern light specified in Rule 10 (a). 
(ii) If sailing vessels, shall carry a white light in a lantern 
so constructed as to show a clear, uniform, and unbroken light 
all round the horizon, and shall also, on the approach of or to 
other vessels show, where it can best be seen, a white flare-up light 
in sufficient time to prevent collision. 
(iii) By day, each of the foregoing vessels shall show, where 
it can best be seen, a basket. 
(f) In addition to the lights which they are by this Rule required 
to show vessels fishing may, if necessary in order to attract attention 
of approaching vessels, show a flare-up light. 
They may also use 
working lights. 
(g) Every vessel fishing, when at anchor, shall show the lights or 
shape specified in Rule 11 (a), (b) or (c) ; and shall, on the approach 
of another vessel or vessels, show an additional white light at least 
6 ffeet below the forward anchor light and at a horizontal distance 
of at least 10 feet away from it in the direction of the outlying gear. 
414 
PUBLIC LAW 172—OCT. 11, 1951 
[65 STAT. 
(h) If a vessel when fishing becomes fast by her gear to a rock or 
other obstruction she shall in daytime haul down the basket required 
by sections (c), (d) or (e) and show the signal specified in Rule 11 
(c). 
By night she shall show the light or lights specified in Rule 11 
(a) or (b). In fog, mist, falling snow, heavy rainstorms or any other 
condition similarly restricting visibility, whether by day or by night, 
she shall sound the signal prescribed by Rule 15 (c) (v), which signal 
shall also be used, on the near approach of another vessel, in good 
visibility. 
NOTE.—For fog signals for fishing vessels, see Rule 15 (c) (ix). 
RULE 10 
(a) A vessel when under way shall carry at her stern a white light, 
so constructed that it shall show an unbroken light over an arc of the 
horizon of 12 points of the compass (135 degrees), so fixed as to show 
the light 6 points (67i/2 degrees) from right aft on each side of the 
vessel, and of such a character as to be visible at a distance of at least 
2 miles. Such light shall be carried as nearly as practicable on the 
same level as the sidelights. 
NOTE.—For vessels engaged in towing or being towed, see Rules 
3 (b) and 5. 
(b) In a small vessel, if it is not possible on account of bad weather 
or other sufficient cause for this light to be fixed, an electric torch 
or a lighted lantern shall be kept at hand ready for use and shall, on 
the approach of an overtaking vessel, be shown in sufficient time to 
prevent collision. 
(c) A seaplane on the water when under way shall carry on her 
tail a white light, so constructed as to show an unbroken light over 
an arc of the horizon of 140 degrees of the compass, so fixed as to 
show the light 70 degrees from right aft on each side of the seaplane, 
and of such a character as to be visible at a distance of at least 2 miles. 
RULE 11 
(a) A vessel under 150 feet in length, when at anchor, shall carry 
in the forepart of the vessel, where it can best be seen, a white light 
in a lantern so constructed as to show a clear, uniform, and unbroken 
light visible all round the horizon at a distance of at least 2 miles. 
(b) A vessel of 150 feet or upwards in length, when at anchor, shall 
carry in the forepart of the vessel, at a height of not less than 20 
feet above the hull, one such light, and at or near the stem of the 
vessel and at such a height that it shall be not less than 15 feet lower 
than the forward light, another such light. 
Both these lights shall 
be visible all round the horizon at a distance of at least 3 miles, 
(c) Between sunrise and sunset every vessel when at anchor shall 
carry in the forepart of the vessel, where it can best been seen, one 
black ball not less than 2 feet in diameter. 
(d) A vessel engaged in laying or in picking up a submarine cable 
or navigation mark, or a vessel engaged in surveying or underwater 
operations, when at anchor, shall carry the lights or shapes prescribed 
in Rule 4 (c) in addition to those prescribed in the appropriate pre-
ceding sections of this Rule. 
(e) A vessel aground shall carry by night the light or lights pre-
scribed in sections (a) or (b) and the two red lights prescribed in 
Rule 4 (a). By day she shall carry, where they can best be seen, 
three black balls, each not less than 2 feet in diameter, placed in a 
vertical line one over the other, not less than 6 feet apart. 
65 STAT.] 
PUBLIC LAW 172—OCT. 11, 1951 
415 
(f) A seaplane on the water under 150 feet in length, when at 
anchor, shall carry, where it can best be seen, a white light, visible 
all round the horizon at a distance of at least 2 miles. 
(g) A seaplane on the water 150 feet or upwards in length, when 
at anchor, shall carry, where they can best be seen, a white light for-
ward and a white light aft, both lights visible all round the norizon 
at a distance of at least 3 miles; and, in addition, if the seaplane is 
more than 150 feet in span, a white light on each side to indicate the 
maximum span, and visible, so far as practicable, all round the horizon 
at a distance of 1 mile. 
(h) A seaplane aground shall carry an anchor light or lights as 
prescribed in sections (f) and (g), and in addition may carry two 
red lights in a vertical line, at least 3 feet apart, so placed as to be 
visible all round the horizon. 
BULE 12 
Every vessel or seaplane on the water may, if necessary in order 
to attract attention, in addition to the lights which she is by these 
Rules required to carry, show a flare-up light or use a detonating or 
other efficient sound signal that cannot be mistaken for any signal 
authorised elsewhere under these Rules. 
BULB 13 
(a) Nothing in these Rules shall interfere with the operation of any 
special rules made by the Government of any nation with respect to 
additional station and signal lights for ships of war, for vessels sailing 
under convoy, or for seaplanes on the water; or with the exhibition 
of recognition signals adopted by shipowners, which have been au-
thorised by their respective Governments and duly registered and 
published. 
(b) Whenever the Government concerned shall have determined 
that a naval or other military vessel or water-borne seaplane of special 
construction or purpose cannot comply fully with the provisions of 
any of these Rules with respect to the number, position, range or arc 
of visibility of lights or shapes, without interfering with the military 
function of .the vessel or seaplane, such vessel or seaplane shall comply 
with such other provisions in regard to the number, position, range or 
arc of visibility of lights or shapes as her Government shall have de-
termined to be the closest possible compliance with these Rules in 
respect of that vessel or seaplane. 
BULE 14 
A vessel proceeding under sail, when also being propelled by 
machinery, shall carry in the daytime forward, where it can best be 
seen, one black conical shape, point upwards, not less than 2 feet in 
diameter at its base. 
RULE 15 
(a) A power-driven vessel shall be provided with an efficient whistle, 
sounded by steam or by some substitute for steam, so placed that the 
sound may not be intercepted by any obstruction, and with an efficient 
fog-horn, to be sounded by mechanical means, and also with an 
efficient bell. A sailing vessel of 20 tons or upwards shall be provided 
with a similar fog-horn and bell. 
76100 O - 52 (PT. I) - 29 
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PUBLIC LAW 172—OCT. 11, 1951 
[65 STAT. 
(b) All signals prescribed by this Rule for vessels under way shall 
be given:— 
(i) bv power-driven vessels on the whistle; 
(ii) by sailing vessels on the fog-horn; 
(iii) by vessels towed on the whistle or fog-horn. 
(c) In fog, mist, falling snow, heavy rainstorms, or any other condi-
tion similarly restricting visibility, whether by day or night, the sig-
nals prescribed in this Rule shall be used as follows:— 
(i) A power-driven vessel making way through the water, shall 
sound at intervals of not more than 2 minutes a prolonged blast. 
(ii) A power-driven vessel under way, but stopped and making 
no way through the water, shall sound at intervals of not more 
than 2 minutes two prolonged blasts, with an interval of about 1 
second between them. 
(iii) A sailing vessel under way shall sound, at intervals of 
not more than 1 minute, when on the starboard tack one blast, 
when on the port tack two blasts in succession, and when with the 
wind abaft the beam three blasts in succession. 
(iv) A vessel when at anchor shall at intervals of not more 
than 1 minute ring the bell rapidly for about 5 seconds. In vessels 
of more than 350 feet in length the bell shall be sounded in the 
forepart of the vessel, and in addition there shall be sounded in the 
after part of the vessel, at intervals of not more than 1 minute for 
about 5 seconds, a gong or other instrument, the tone and sounding 
of which cannot be confused with that of the bell. Every vessel 
at anchor may in addition, in accordance with Rule 12, sound three 
blasts in succession, namely, one short, one prolonged, and one 
short blast, to give warning of her position and of the possibility 
of collision to an approaching vessel. 
(v) A vessel when towing, a vessel engaged in laying or in 
picking up a submarine cable or navigation mark, and a vessel 
under way which is unable to get out of the way of an approaching 
vessel through being not under command or unable to manoeuvre 
as required by these Rules shall, instead of the signals prescribed 
in subsections (i), (ii) and (iii) sound, at intervals of not more 
than 1 minute, three blasts in succession, namely, one prolonged 
blast followed by two short blasts. 
(vi) A vessel towed, or, if more than one vessel is towed, only 
the last vessel of the tow, if manned, shall, at intervals of not more 
than 1 minute, sound four blasts in succession, namely, one pro-
longed blast followed by three short blasts. When practicable, 
this signal shall be made immediately after the signal made by 
the towing vessel. 
(vii) A vessel aground shall give the signal prescribed in 
sub-section (iv) and shall, in addition, give three separate and 
distinct strokes on the bell immediately before and after each 
such signal. 
(viii) A vessel of less than 20 tons, a rowing boat, or a seaplane 
on the water, shall not be obliged to give the above-mentioned 
signals, but if she does not, she shall make some other efficient 
sound signal at intervals of not more than 1 minute. 
(ix) A vessel when fishing, if of 20 tons or upwards, shall at 
intervals of not more than 1 minute, sound a blast, such blast to 
be followed by ringing the bell; or she may sound, in lieu of these 
signals, a blast consisting of a series of several alternate notes of 
higher and lower pitch. 
65 STAT.] 
PUBLIC LAW 172—OCT. 11, 1951 
4 1 7 
EULE 16 
Speed to be moderate in fog, &c. 
(a) Every vessel, or seaplane when taxi-ing on the water, shall, in 
fog, mist, falling snow, heavy rainstorms or any other condition 
similarly restricting visibility, go at a moderate speed, having careful 
regard to the existing circumstances and conditions. 
(b) A power-driven vessel hearing, apparently forward of her beam, 
the fog-signal of a vessel the position of which is not ascertained, 
shall, so far as the circumstances of the case admit, stop her engines, 
and then navigate with caution until danger of collision is over. 
PART C—STEERING AND SAILING RULES 
PRELIMINARY 
1. In obeying and construing these Rules, any action taken should 
be positive, in ample time, and with due regard to the observance of 
good seamanship. 
2. Risk of collision can, when circumstances permit, be ascertained 
by carefully watching the compass bearing of an approaching vessel. 
If the bearing does not appreciably change, such risk should be deemed 
to exist. 
3. Mariners should bear in mind that seaplanes in the act of landing 
or taking off, or operating under adverse weather conditions, may be 
unable to change their intended action at the last moment. 
RULE 17 
When two sailing vessels are approaching one another, so as to 
involve risk of collision, one of them shall keep out of the way of the 
other, as follows:— 
(a) A vessel which is running free shall keep out of the way of a 
vessel which is close-hauled. 
(b) A vessel which is close-hauled on the port tack shall keep out 
of the way of a vessel which is close-hauled on the starboard tack. 
(c) When both are running free, with the wind on different sides, 
the vessel which has the wind on the port side shall keep out of the 
way of the other. 
(d) When both are running free, with the wind on the same side, 
the vessel which is to windward shall keep out of the way of the 
vessel which is to leeward. 
(e) A vessel which has the wind aft shall keep out of the way of 
the other vessel. 
RULE 18 
(a) When two power-driven vessels are meeting end on, or nearly 
end on, so as to involve risk of collision, each shall alter her course to 
starboard, so that each may pass on the port side of the other. 
This 
Rule only applies to cases where vessels are meeting end on, or nearly 
end on, in such a manner as to involve risk of collision, and does not 
apply to two vessels which must, if both keep on their respective 
courses, pass clear of each other. The only cases to which it does apply 
are when each of two vessels is end on, or nearly end on, to the other; 
in other words, to cases in which, by day, each vessel sees the masts 
of the other in a line, or nearly in a line, with her own; and by 
night, to cases in which each vessel is in such a position as to see both 
the sidelights of the other. 
It does not apply, by day, to cases in 
418 
PUBLIC LAW 172—OCT. 11, 1951 
[65 STAT. 
which a vessel sees another ahead crossing her own course; or, by 
night, to cases where the red light of one vessel is opposed to the 
red light of the other or where the green light of one vessel is opposed 
to the green light of the other or where a red light without a green 
light or a green light without a red light is seen ahead, or where both 
green and red lights are seen anywhere but ahead. 
(b) For the purposes of this Rule and Rules 19 to 29 inclusive, 
except Rule 20 (b), a seaplane on the water shall be deemed to be a 
vessel, and the expression "power-driven vessel" shall be construed 
accordingly. 
RUIiE 19 
When two power-driven vessels are crossing, so as to involve risk 
of collision, the vessel which has the other on her own starboard side 
shall keep out of the way of the other. 
RULE 20 
(a) When a power-driven vessel and a sailing vessel are proceeding 
in such directions as to involve risk of collision, except as provided in 
Rules 24 and 26, the power-driven vessel shall keep out of the way 
of the sailing vessel. 
(b) A seaplane on the water shall, in general, keep well clear of 
all vessels and avoid impeding their navigation. 
In circumstances, 
however, where risk of collision exists, she shall comply with these 
Rules. 
RULE 21 
Where by any of these Rules one of two vessels is to keep out of the 
way, the other shall keep her course and speed. When, from any 
cause, the latter vessel finds herself so close that collision cannot be 
avoided by the action of the giving-way vessel alone, she also shall 
take such action as will best aid to avert collision (see Rules 27 and 29). 
RULE 22 
Every vessel which is directed by these Rules to keep out of the way 
of another vessel shall, if the circumstances of the case admit, avoid 
crossing ahead of the other. 
RULE 23 
Every power-driven vessel which is directed by these Rules to keep 
out of the way of another vessel shall, on approaching her, if necessary, 
slacken her speed or stop or reverse. 
RULE 24 
(a) Notwithstanding anything contained in these Rules, every vessel 
overtaking any other shall keep out of the way of the overtaken vessel. 
(b) Every vessel coming up with another vessel from any direction 
more than 2 points (221/2 degrees) abaft her beam, i. e. in such a posi-
tion, with reference to the vessel which she is overtaking, that at night 
she would be unable to see either of that vessel's sidelights, shall be 
deemed to be an overtaking vessel; and no subsequent alteration of the 
bearing between the two vessels shall make the overtaking vessel a 
crossing vessel within the meaning of these Rules, or relieve her of the 
duty of keeping clear of the overtaken vessel until she is finally past 
and clear. 
66 STAT.] 
PUBLIC LAW 172—OCT. 11, 1951 
419 
(c) If the overtaking vessel cannot determine with certainty 
whether she is forward of or abaft this direction from the other vessel, 
she shall assume that she is an overtaking vessel and keep out of the 
way. 
RULE 25 
(a) In a narrow channel every power-driven vessel when proceeding 
along the course of the channel shall, when it is safe and practicable, 
keep to that side of the fairway or mid-channel which lies on the star-
board side of such vessel. 
(b) Whenever a power-driven vessel is nearing a bend in a channel 
where a power-driven vessel approaching from the other direction 
cannot be seen, such vessel, when she shall have arrived within one-
half mile of the bend, shall give a signal by one prolonged blast of her 
whistle, which signal shall be answered by a similar blast given by any 
approaching power-driven vessel that may be within hearing around 
the bend. Regardless of whether an approaching vessel on the farther 
side of the bend is heard, such bend shall be rounded with alertness 
and caution. 
RULE 2 6 
All vessels not engaged in fishing shall, when under way, keep out 
of the way of any vessels fishing with nets or lines or trawls. This 
Rule shall not give to any vessel engaged in fishing the right of 
obstructing a fairway used by vessels other than fishing; vessels. 
RUIiE 27 
In obeying and construing these Rules due regard shall be had to all 
dangers of navigation and collision, and to any special circumstances, 
including the limitations of the craft involved, which may render a 
departure from the above Rules necessary in order to avoid immediate 
danger. 
PART D.—MISCELLANEOUS 
RULE 
28 
(a) When vessels are in sight of one another, a power-driven vessel 
under way, in taking any course authorised or required by these Rules, 
shall indicate that course by the following signals on her whistle, 
namely:— 
One short blast to mean "I am altering my course to starboard." 
Two short blasts to mean "I am altering my course to port." 
Three short blasts to mean "My engines are going astern." 
(b) Whenever a power-driven vessel which, under these Rules, is 
to keep her course and speed, is in sight of another vessel and is in 
doubt whether sufficient action is being taken by the other vessel to 
avert collision, she may indicate such doubt by giving at least five short 
and rapid blasts on the whistle. The giving of such a signal shall not 
relieve a vessel of her obligations under Rules 27 and 29 or any other 
Rule, or of her duty to indicate any action taken under these Rules 
by giving the appropriate sound signals laid down in this Rule. 
(c) Nothing in these Rules shall interfere with the operation of 
any special rules made by the Government of any nation with respect 
to the use of additional whistle signals between ships of war or vessels 
sailing under convoy. 
RULE 29 
Nothing in these Rules shall exonerate any vessel, or the owner, 
master or crew thereof, from the consequences of any neglect to carry 
4 2 0 
PUBLIC LAW 173—OCT. 12, 1961 
[65 STAT. 
lights or signals, or of any neglect to keep a proper look-out, or of the 
neglect of any precaution which may be required by the ordinary 
practice of seamen, or by the special circumstances of the case. 
RULE 30 
Reservation of Rules for Harbours and Inland Navigation 
Nothing in these Rules shall interfere with the operation of a special 
rule duly made by local authority relative to the navigation of any 
harbour, river, lake, or inland water, including a reserved seaplane 
area. 
RULE 31 
Distress Signals 
When a vessel or seaplane on the water is in distress and requires 
assistance from other vessels or from the shore, the following shall be 
the signals to be used or displayed by her, either together or separately, 
namely:— 
(a) A gun or other explosive signal fired at intervals of about a 
minute. 
• (b) A continuous sounding with any fog-signal apparatus. 
(c) Rockets or shells, throwing red stars fired one at a time at short 
intervals. 
(d) A signal made by radiotelegraphy or by any other signalling 
method consisting of the group . . . 
. . . in the Morse Code. 
(e) A signal sent by radiotelephony consisting of the spoken word 
"Mayday." 
(f) The International Code Signal of distress indicated by N.C. 
(g) A signal consisting of a square flag having above or below it a 
ball or anything resembling a ball. 
(h) Flames on the vessel (as from a burning tar barrel, oil barrel, 
&c.). 
(i) A rocket parachute flare showing a red light. 
The use of any of the above signals, except for the purpose of 
indicating that a vessel or a seaplane is in distress, and the use of any 
signals which may be confused with any of the above signals, is 
prohibited. 
Note.—A radio signal has been provided for use by vessels in distress 
for the purpose of actuating the auto-alarms of other vessels and thus 
securing attention to distress calls or messages. The signal consists 
of a series of twelve dashes, sent in 1 minute, the duration of each dash 
being 4 seconds, and the duration of the interval between two consecu-
tive dashes 1 second. 
RULE 32 
All orders to helmsmen shall be given in the following sense: right 
rudder or starboard to mean "put the vessel's rudder to starboard"; 
left rudder or port to mean "put the vessel's rudder to port." 
Approved October 11, 1951. 
Public Law 173 
CHAPTER 498 
AN ACT 
October 12, 1951 
IS. 1994] 
To authorize the use of the incompleted submarine Ulua as a target for explosive 
tests, and for other purposes. 
Be it enacted hy the Senate and House of Representatives 
of the 
use'^oP^su^bmartae United States of America in Congress assembled, That notwithstand-
uiua as target. 
ing the proviso of title I I I of the Second Supplemental Surplus