Rule 30 — Anchor Lights, Aground Signals, and Moored Barges

What the rule requires

The vessel at anchor

Two all-round white lights, and their relative height is the tested detail. A vessel at anchor exhibits, where it can best be seen, an all-round white light or one ball in the fore part, and at or near the stern at a lower level than the forward light, a second all-round white light 33 CFR §83.30. Forward light high, after light low. A candidate who remembers only "two whites" loses the question that offers the pair reversed.

A vessel of less than 50 meters in length may exhibit a single all-round white light where it can best be seen instead of the two. The verb is may: a 40-meter vessel showing the full fore-and-aft pair is equally compliant, and an option written as a permission does not become a requirement because most operators take it. This paragraph reads word for word the same internationally COLREGs Rule 30, so a question on anchor lights for a vessel under 50 meters has the same answer whether it is labelled International, Inland, or both.

Deck lighting splits on a different number. Any vessel at anchor may use her available working or equivalent lights to illuminate her decks; a vessel of 100 meters or more in length shall . Two thresholds, two different jobs: 50 meters governs how many anchor lights, 100 meters governs deck illumination.

An "all-round light" is one showing an unbroken light over an arc of 360 degrees COLREGs Rule 21. Under the International rule the minimum visibility for a white all-round light is 3 miles in vessels of 50 meters or more, 2 miles in vessels of 12 meters or more but less than 50 meters, and 2 miles in vessels of less than 12 meters COLREGs Rule 22. Those ranges are set by required intensity, not derived from anything; learn them cold. Rule 22 is one of the rules where the Inland text is not word for word the same as the International, so treat a range question as regime-specific and read the label before answering.

The vessel aground

She shows everything she would show at anchor, and then the aground signals on top of it. A vessel aground exhibits the lights prescribed in paragraph (a) or (b) and in addition, if practicable, where they can best be seen, two all-round red lights in a vertical line and three balls in a vertical line . The supplied International text of Rule 30 covers only the anchored-vessel paragraphs, so the aground requirements stated here rest on the Inland rule.

Splitting that by time of day is what the exam actually asks. Lights are exhibited from sunset to sunrise, and shapes are complied with by day COLREGs Rule 20. So the aground vessel's night signal is her anchor light or lights plus two all-round red in a vertical line, and her day signal is three balls in a vertical line. Rule 20 is word-for-word identical in the Inland rules, which makes the day/night division safe to apply under either regime.

Fog by daylight brings the lights back up. Lights prescribed by the Rules shall, if carried, also be exhibited from sunrise to sunset in restricted visibility, and may be exhibited whenever it is deemed necessary. A vessel anchored in a fairway at 1000 in half a mile of visibility exhibits her anchor light, not merely her ball.

You are aground at 0200 on a 40-meter uninspected passenger vessel in Inland waters. What must you exhibit?

One all-round white light where it can best be seen (permitted in lieu of the fore-and-aft pair because she is under 50 meters), plus two all-round red lights in a vertical line. Balls are day shapes and have no place at 0200. The two reds do not replace the anchor light; paragraph (d) requires the anchor signal "in addition" to them.

Moored barges — Inland only

These paragraphs appear in the Inland rule and drive a distinct set of questions, all of them numerical. Four conditions put barge lights on: a barge projecting into a buoyed or restricted channel; a barge so moored that it reduces the available navigable width of any channel to less than 80 meters; barges moored in groups more than two barges wide, or to a maximum width of over 25 meters; and any barge not moored parallel to the bank or dock . The lights are two unobstructed all-round white lights of an intensity to be visible for at least 1 nautical mile, meeting Annex I (33 CFR part 84), displayed at night and if practicable in periods of restricted visibility.

That 1 nautical mile is the trap. It is a barge-lighting figure and it does not match the vessel ranges of Rule 22.

A barge or group at anchor, or made fast to mooring buoys or a similar device, may instead carry all-round white lights of the same 1-mile intensity arranged to mark extremities: a barge projecting from a group formation is lighted on its outboard corners, and where other vessels normally navigate on both sides, the lights mark the corner extremities of the barge or of the group.

Four exemptions run the other way. A barge or group moored in a slip or slough used primarily for mooring, one moored behind a pierhead, a barge less than 20 meters moored in a special anchorage area designated under §109.10, and barges moored in the well-illuminated areas the rule lists by name and river mile on the Chicago Sanitary Ship Canal, the Calumet Sag Channel, the Little Calumet, the Calumet and the Cumberland Rivers. Nobody is asked to recite mile markers; be able to recognise "well-illuminated areas named in the rule" as a genuine exemption rather than a distractor.

Telling it apart

Three length thresholds sit in this one rule, each exempting a different vessel from a different signal, and mixing them is the most reliable way to lose a Rule 30 question. The criterion that separates them is what condition the vessel is in 33 CFR §83.30.

Less than 7 meters — at anchor. Not required to exhibit the anchor lights or shape, but only when she is not in or near a narrow channel, fairway, anchorage, or where other vessels normally navigate. Most often misfiled as a blanket exemption for small craft. A 6-meter skiff anchored in an anchorage shows the light.
Less than 12 meters — aground. Not required to exhibit the two all-round red lights or the three balls. She is still an anchored vessel for the purposes of paragraphs (a) and (b), so the anchor light stays up. Candidates read this as excusing her from everything.
Less than 20 meters — at anchor in a special anchorage area designated by the Coast Guard. Not required to exhibit the anchor lights and shapes required by this Rule. Misfiled by applying it in any anchorage; the area must be a designated special anchorage.

The barge exemption at less than 20 meters in a special anchorage under §109.10 is a fourth use of a familiar number, and it applies to barges, not to the vessel-at-anchor case above it.

Working a question

A 30-meter towing vessel takes the ground on a shoal in Inland waters at 1500 in half a mile of visibility. Decide her signals in order.

Is she aground, or merely anchored? Aground. Paragraph (d) is triggered, which means the anchor signals of (a) or (b) and the additional aground signals.
Does a length exemption apply? She is 30 meters. The aground exemption stops at 12 meters, so nothing is excused. Had she been 11 meters, the two reds and the three balls would come off and the anchor signal would stay.
Which anchor signal may she use? Under 50 meters, so a single all-round white light where it can best be seen satisfies (b) at night; the fore-and-aft pair remains lawful.
What is the time of day? 1500, so shapes govern: three balls in a vertical line.
What does the visibility do? Half a mile is restricted visibility, and lights carried shall also be exhibited from sunrise to sunset in restricted visibility COLREGs Rule 20. Her lights go on as well as the shapes: the all-round white plus two all-round red in a vertical line.
What intensity must those lights make? At 30 meters she falls in the 12-to-50-meter band, so 2 miles for a white or red all-round light under the International rule COLREGs Rule 22.

At sunset the shapes come down and the lights alone carry the message; at sunrise, if the fog has cleared, the lights come down and the balls go up.

Where candidates lose the point

Answering "two all-round red lights in a vertical line" and nothing else for a vessel aground at night. It is the signal that identifies the condition, so it looks complete. Paragraph (d) requires the lights of (a) or (b) in addition, which is why the correct option always includes the anchor light 33 CFR §83.30.

Putting the three balls up at night, or the two reds up in clear daylight. Shapes are day signals and lights run sunset to sunrise; the only crossover is lights by day in restricted visibility COLREGs Rule 20.

Reading the under-50-meter single white light as reaching the aground signals. It substitutes for paragraph (a) only. The two reds and the three balls stand on their own regardless of length down to the 12-meter exemption.

Treating the under-7-meter exemption as unconditional. The qualifier is four-part and each part is disqualifying: narrow channel, fairway, anchorage, or where other vessels normally navigate. An exam question that mentions any of them has already answered itself.

Reversing the two anchor lights. The forward light is the higher and the after light is the lower. An option showing the after light above the forward light is wrong on that ground alone.

Applying Rule 22's 2- and 3-mile ranges to Inland barge lights. Moored barge lights are specified at 1 nautical mile and meet Annex I, 33 CFR part 84 .

Making deck illumination mandatory for everyone at anchor. It is permissive below 100 meters and required at 100 meters or more.

Check yourself

Your 45-meter vessel is anchored in an open roadstead at 2200. Which of the following is NOT compliant?

A single all-round white light where it can best be seen is compliant (under 50 meters). The fore-and-aft pair with the forward light higher is compliant. A pair with the after light higher than the forward light is not: paragraph (a)(ii) fixes the after light at a lower level than the forward one.

By day, a vessel displays one ball forward and three balls in a vertical line. What is her condition?

Aground. The three balls in a vertical line are the aground day signal, carried in addition to the anchor signal of paragraph (a) or (b).

You run your 10-meter workboat aground in daylight in Inland waters. What are you required to display?

Nothing on account of being aground. A vessel of less than 12 meters when aground is not required to exhibit the two all-round red lights or the three balls. The anchor requirements of paragraphs (a) and (b) are not lifted at that length — the 7-meter exemption is the one that touches those, and only when clear of channels, fairways, anchorages and waters where other vessels normally navigate.

It is 1100 with visibility down to 400 yards. You are anchored in a fairway. Is your anchor light required?

Yes. Lights prescribed by the Rules shall, if carried, also be exhibited from sunrise to sunset in restricted visibility. The ball is required by day in its own right; the light joins it because the visibility is restricted.

A barge is moored so that the navigable width of the channel is reduced to 70 meters. What must she display, and to what range?

Two unobstructed all-round white lights meeting Annex I (33 CFR part 84), visible at least 1 nautical mile, at night and if practicable in restricted visibility. The trigger is any mooring that reduces available navigable width to less than 80 meters. This is an Inland provision.

Your 120-meter vessel comes to anchor. Beyond the anchor lights, what else does the rule require?

Use of the available working or equivalent lights to illuminate her decks. At 100 meters or more it is mandatory; below that length it is at the master's discretion.

An 18-meter vessel anchors in a special anchorage area designated by the Coast Guard. Anchor light required?

No. A vessel of less than 20 meters at anchor in a designated special anchorage area is not required to exhibit the anchor lights and shapes required by this Rule. Change the facts to an ordinary anchorage and the exemption evaporates.