Comparisons
NUC vs RAM — definitions, lights, shapes
Comparison study notes and reference passages. Read the linked complete rules, including qualifications, exceptions and any publication notes; translated study text is not an official instrument.
(f) The term vessel not under command means a vessel which through some exceptional circumstance is unable to maneuver as required by these Rules and is therefore unable to keep out of the way of another vessel.
(g) The term vessel restricted in her ability to maneuver means a vessel which from the nature of her work is restricted in her ability to maneuver as required by these Rules and is therefore unable to keep out of the way of another vessel. The term vessels restricted in their ability to maneuver shall include but not be limited to:
Rule 18 does not rank NUC above RAM. Its opening exceptions are Rules 9, 10 and 13; fishing vessels underway keep clear of NUC/RAM so far as possible. Equipment failure only creates NUC when Rule 3(f) is actually met; responsibility under Rule 2 remains.
NUC vs RAM — definitions, lights, shapes
| Aspect | NUC — Not Under Command | RAM — Restricted in Ability to Manoeuvre |
|---|---|---|
| 3(f) / 3(g) | (f) The term vessel not under command means a vessel which through some exceptional circumstance is unable to maneuver as required by these Rules and is therefore unable to keep out of the way of another vessel. | (g) The term vessel restricted in her ability to maneuver means a vessel which from the nature of her work is restricted in her ability to maneuver as required by these Rules and is therefore unable to keep out of the way of another vessel. The term vessels restricted in their ability to maneuver shall include but not be limited to: |
| 27(a) / 27(b) | NUC: two all-round red lights and two black balls vertically. When making way, add sidelights and sternlight, without masthead lights. Rule 27(g) provides the under-12 m exemption except diving vessels. | RAM other than mine clearance: red-white-red all-round lights and ball-diamond-ball. When making way, add masthead light(s), sidelights and sternlight. Rule 27(b)(iv) adds anchor signals; dredging/underwater operations have the distinct provisions of 27(d), and mine clearance uses 27(f). |
| 18 | Rule 18 does not rank NUC above RAM. Its opening exceptions are Rules 9, 10 and 13; fishing vessels underway keep clear of NUC/RAM so far as possible. Equipment failure only creates NUC when Rule 3(f) is actually met; responsibility under Rule 2 remains. | Rule 18 does not rank NUC above RAM. Its opening exceptions are Rules 9, 10 and 13; fishing vessels underway keep clear of NUC/RAM so far as possible. Equipment failure only creates NUC when Rule 3(f) is actually met; responsibility under Rule 2 remains. |
| 35(c)–(g) | (c) A vessel not under command, a vessel restricted in her ability to maneuver, a vessel constrained by her draft, a sailing vessel, a vessel engaged in fishing and a vessel engaged in towing or pushing another vessel shall, instead of the signals prescribed in paragraphs (a) or (b) of this Rule, sound at intervals of not more than 2 minutes three blasts in succession, namely one prolonged followed by two short blasts. (g) A vessel at anchor shall at intervals of not more than one minute ring the bell rapidly for about 5 seconds. In a vessel of 100 meters or more in length the bell shall be sounded in the forepart of the vessel and immediately after the ringing of the bell the gong shall be sounded rapidly for about 5 seconds in the after part of the vessel. A vessel at anchor may in addition 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. | (c) A vessel not under command, a vessel restricted in her ability to maneuver, a vessel constrained by her draft, a sailing vessel, a vessel engaged in fishing and a vessel engaged in towing or pushing another vessel shall, instead of the signals prescribed in paragraphs (a) or (b) of this Rule, sound at intervals of not more than 2 minutes three blasts in succession, namely one prolonged followed by two short blasts. (d) A vessel engaged in fishing, when at anchor, and a vessel restricted in her ability to maneuver when carrying out her work at anchor, shall instead of the signals prescribed in paragraph (g) of this Rule sound the signal prescribed in paragraph (c) of this Rule. (g) A vessel at anchor shall at intervals of not more than one minute ring the bell rapidly for about 5 seconds. In a vessel of 100 meters or more in length the bell shall be sounded in the forepart of the vessel and immediately after the ringing of the bell the gong shall be sounded rapidly for about 5 seconds in the after part of the vessel. A vessel at anchor may in addition 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. |
3 · 18 · 27 · 35
Rule 18 does not rank NUC above RAM. Its opening exceptions are Rules 9, 10 and 13; fishing vessels underway keep clear of NUC/RAM so far as possible. Equipment failure only creates NUC when Rule 3(f) is actually met; responsibility under Rule 2 remains.
- (g) Vessels of less than 12 meters in length, except those engaged in diving operations, shall not be required to exhibit the lights and shapes prescribed in this Rule.
- (c) A power-driven vessel engaged in a towing operation such as severely restricts the towing vessel and her tow in their ability to deviate from their course shall, in addition to the lights or shapes prescribed in Rule 24(a), exhibit the lights or shapes prescribed in subparagraphs (b)(i) and (ii) of this Rule.
- (d) A vessel engaged in dredging or underwater operations, when restricted in her ability to maneuver, shall exhibit the lights and shapes prescribed in subparagraphs (b)(i), (ii) and (iii) of this Rule and shall in addition, when an obstruction exists, exhibit: (i) two all-round red lights or two balls in a vertical line to indicate the side on which the obstruction exists; (ii) two all-round green lights or two diamonds in a vertical line to indicate the side on which another vessel may pass; (iii) when at anchor, the lights or shapes prescribed in this paragraph instead of the lights or shape prescribed in Rule 30.
Read the underlying rules
Frequently asked questions
What does NUC mean on a vessel?
(f) The term vessel not under command means a vessel which through some exceptional circumstance is unable to maneuver as required by these Rules and is therefore unable to keep out of the way of another vessel.
What does RAM mean on a vessel?
(g) The term vessel restricted in her ability to maneuver means a vessel which from the nature of her work is restricted in her ability to maneuver as required by these Rules and is therefore unable to keep out of the way of another vessel. The term vessels restricted in their ability to maneuver shall include but not be limited to: RAM other than mine clearance: red-white-red all-round lights and ball-diamond-ball. When making way, add masthead light(s), sidelights and sternlight. Rule 27(b)(iv) adds anchor signals; dredging/underwater operations have the distinct provisions of 27(d), and mine clearance uses 27(f).
What lights does a NUC vessel show?
NUC: two all-round red lights and two black balls vertically. When making way, add sidelights and sternlight, without masthead lights. Rule 27(g) provides the under-12 m exemption except diving vessels.
What lights does a RAM vessel show?
RAM other than mine clearance: red-white-red all-round lights and ball-diamond-ball. When making way, add masthead light(s), sidelights and sternlight. Rule 27(b)(iv) adds anchor signals; dredging/underwater operations have the distinct provisions of 27(d), and mine clearance uses 27(f). (d) A vessel engaged in dredging or underwater operations, when restricted in her ability to maneuver, shall exhibit the lights and shapes prescribed in subparagraphs (b)(i), (ii) and (iii) of this Rule and shall in addition, when an obstruction exists, exhibit:
(i) two all-round red lights or two balls in a vertical line to indicate the side on which the obstruction exists;
(ii) two all-round green lights or two diamonds in a vertical line to indicate the side on which another vessel may pass;
(iii) when at anchor, the lights or shapes prescribed in this paragraph instead of the lights or shape prescribed in Rule 30.
What is the difference between NUC and RAM lights?
NUC: two all-round red lights and two black balls vertically. When making way, add sidelights and sternlight, without masthead lights. Rule 27(g) provides the under-12 m exemption except diving vessels. RAM other than mine clearance: red-white-red all-round lights and ball-diamond-ball. When making way, add masthead light(s), sidelights and sternlight. Rule 27(b)(iv) adds anchor signals; dredging/underwater operations have the distinct provisions of 27(d), and mine clearance uses 27(f).
What are the NUC and RAM day shapes?
NUC: two all-round red lights and two black balls vertically. When making way, add sidelights and sternlight, without masthead lights. Rule 27(g) provides the under-12 m exemption except diving vessels. RAM other than mine clearance: red-white-red all-round lights and ball-diamond-ball. When making way, add masthead light(s), sidelights and sternlight. Rule 27(b)(iv) adds anchor signals; dredging/underwater operations have the distinct provisions of 27(d), and mine clearance uses 27(f).
Which has priority — NUC or RAM?
Rule 18 does not rank NUC above RAM. Its opening exceptions are Rules 9, 10 and 13; fishing vessels underway keep clear of NUC/RAM so far as possible. Equipment failure only creates NUC when Rule 3(f) is actually met; responsibility under Rule 2 remains.
Is a fishing vessel NUC or RAM?
(d) The term vessel engaged in fishing means any vessel fishing with nets, lines, trawls or other fishing apparatus which restrict maneuverability, but does not include a vessel fishing with trolling lines or other fishing apparatus which do not restrict maneuverability. Rule 18 does not rank NUC above RAM. Its opening exceptions are Rules 9, 10 and 13; fishing vessels underway keep clear of NUC/RAM so far as possible. Equipment failure only creates NUC when Rule 3(f) is actually met; responsibility under Rule 2 remains.
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