Light Characteristics

Question 1

What is a masthead light?

Answer 1

A white light placed over the fore-and-aft centerline of the vessel.
Definition: Shows an unbroken light over an arc of the horizon of 225°, from right ahead to 22.5° abaft the beam on both sides.
Range:
≥ 50 m vessel: 6 nm
≥ 20 m but < 50 m: 5 nm
< 20 m: 3 nm
< 12 m: 2 nm
Rule reference: Rule 21(a).

Question 2

What is a sidelight?

Answer 2

➡ A green light (starboard) and a red light (port).
Arc: 112.5° (from right ahead to 22.5° abaft the beam on that side).
Range:
≥ 50 m vessel: 3 nm
≥ 20 m but < 50 m: 2 nm
< 20 m: 2 nm
< 12 m: 1 nm
Rule reference: Rule 21(b).

Question 3

What is a sternlight?

Answer 3

➡ A white light at the stern of the vessel.
Arc: 135° (from right aft, 67.5° to each side).
Range:
≥ 50 m vessel: 3 nm
< 50 m vessel: 2 nm
Rule reference: Rule 21(c).

Question 4

What is a towing light?

Answer 4

➡ A yellow light with the same characteristics as the sternlight.
Arc: 135° (from right aft, 67.5° each side).
Range:
≥ 50 m vessel: 3 nm
< 50 m vessel: 2 nm
Rule reference: Rule 21(d).

Question 5

What is an all-round light?

Answer 5

➡ A light showing an unbroken arc of 360° over the horizon.
Arc: 360°
Range:
≥ 50 m vessel: 3 nm
< 50 m vessel: 2 nm
Colors: White, red, green, or yellow depending on use (NUC, RAM, anchor, etc.).
Rule reference: Rule 21(e).

Question 6

What is a flashing light (as defined in COLREGs)?

Answer 6

➡ A light flashing at 120 or more flashes per minute.
Arc: 360°
Range: As for an all-round light (2–3 nm depending on vessel size).
Use: Air-cushion vessels when operating non-displacement mode, hovercraft.
Rule reference: Rule 21(f).

Question 7

What are the required minimum ranges of visibility for navigation lights on vessels ≥ 50 m?

Answer 7

➡ Masthead – 6 nm
➡ Sidelights – 3 nm
➡ Sternlight – 3 nm
➡ Towing light – 3 nm
➡ All-round – 3 nm

Question 8

What are the required minimum ranges of visibility for vessels ≥ 12 m but < 50 m?

Answer 8

➡ Masthead – 5 nm if ≥ 20 m, 3 nm if < 20 m
➡ Sidelights – 2 nm
➡ Sternlight – 2 nm
➡ Towing light – 2 nm
➡ All-round – 2 nm

Question 9

What are the required minimum ranges of visibility for vessels < 12 m?

Answer 9

➡ Masthead – 2 nm
➡ Sidelights – 1 nm
➡ Sternlight – 2 nm
➡ Towing light – 2 nm
➡ All-round – 2 nm

Question 10

What lights does a power-driven vessel underway show?

Answer 10

➡ Masthead light(s): white, unbroken over 225°.
One masthead light forward.
A second masthead light abaft of and higher than the forward one if ≥ 50 m.
➡ Sidelights: port red, starboard green, each unbroken over 112.5°.
➡ Sternlight: white, unbroken over 135°.
Vertical separation: second masthead at least 4.5 m higher than forward, or ≥ 1 ship’s breadth if > 50 m beam.
Rule reference: Rule 23(a).

Question 11

What lights does a vessel restricted in ability to manoeuvre (RAM) show?

Answer 11

➡ Three all-round lights in a vertical line:
Red (top), white (middle), red (bottom).
➡ When making way: also masthead light(s), sidelights, sternlight.
➡ When at anchor: also anchor lights.
➡ When engaged in underwater operations: two all-round red lights on obstructed side and two all-round green lights on safe-passing side (horizontal separation).
Vertical separation: 2 m if ≥ 20 m vessel.
Horizontal separation: ≥ 2 m between red/green pairs.
Rule reference: Rule 27(b).

Question 12

What lights does a sailing vessel underway show?

Answer 12

➡ Sidelights (red & green, unbroken 112.5°).
➡ Sternlight (white, unbroken 135°).
➡ Optional: Two all-round lights in a vertical line at or near top of mast:
Upper red, lower green (but not in addition to normal lights).
➡ Vessels < 20 m may combine sidelights in one lantern carried forward.
Rule reference: Rule 25(a).

Question 13

What lights does a power-driven vessel < 12 m show?

Answer 13

➡ May show:
One all-round white light (unbroken 360°) and sidelights.
➡ Instead of full setup with masthead + sternlight.
Rule reference: Rule 23(d).

Question 14

What lights does a vessel under oars show?

Answer 14

➡ May exhibit sidelights and sternlight.
➡ Otherwise, must have ready at hand an electric torch or lantern showing a white light, to be displayed in time to avoid collision.
Rule reference: Rule 25(d).

Question 15

What lights does a vessel constrained by draught show?

Answer 15

➡ Three all-round red lights in a vertical line.
➡ Plus normal power-driven lights (masthead(s), sidelights, sternlight).
Vertical separation: 2 m between lights.
Rule reference: Rule 28.

Question 16

What lights does a trawling vessel show?

Answer 16

➡ Two all-round lights in a vertical line:
Green over white.
➡ If > 50 m: masthead light abaft & higher than all-round lights.
➡ If gear > 150 m: all-round white light in direction of gear.
➡ Plus sidelights + sternlight when making way.
Rule reference: Rule 26(a).

Question 17

What lights does a pilot vessel engaged in duty show?

Answer 17

➡ Two all-round lights in a vertical line:
White over red (“White cap, red trousers, pilot on duty”).
➡ Plus sidelights + sternlight when underway.
➡ When at anchor: add anchor lights.
Rule reference: Rule 29.

Question 18

What lights does a vessel at anchor show?

Answer 18

➡ One all-round white light in the forepart.
➡ One all-round white light in the aft part (higher than forward) if ≥ 50 m.
➡ Vessels < 50 m may show just one all-round white light where best seen.
➡ May also show deck lights.
Vertical separation: aft light higher than fore light.
Rule reference: Rule 30.

Question 19

What lights does a vessel aground show?

Answer 19

➡ Anchor lights (as above).
➡ Plus two all-round red lights in a vertical line.
Rule reference: Rule 30(d).

Question 20

What is the fog signal for a power-driven vessel making way?

Answer 20

➡ One prolonged blast (4–6 seconds).
➡ Interval: every ≤ 2 minutes.
➡ Audible range: up to 2 nm with ship’s whistle (for vessels ≥ 75 m).
➡ Rule 35(a).

Question 21

What is the fog signal for a power-driven vessel underway but stopped (not making way)?

Answer 21

➡ Two prolonged blasts in succession, separated by 2 seconds.
➡ Interval: every ≤ 2 minutes.
➡ Audible range: up to 2 nm.
➡ Rule 35(b).

Question 22

What is the fog signal for a vessel not under command (NUC), restricted in ability to manoeuvre (RAM), constrained by draught, sailing vessel, fishing vessel, or towing/pushing vessel?

Answer 22

➡ One prolonged blast followed by two short blasts.
➡ Interval: every ≤ 2 minutes.
➡ Audible range: up to 2 nm.
➡ Rule 35(c).

Question 23

What is the fog signal for a vessel being towed (last vessel of the tow)?

Answer 23

➡ One prolonged blast followed by three short blasts.
➡ Interval: every ≤ 2 minutes.
➡ Audible range: ~1–1.5 nm (due to smaller whistles).
➡ Rule 35(c).

Question 24

What is the fog signal for a pilot vessel engaged on duty?

Answer 24

➡ Same as vessel type it falls under (usually RAM).
➡ May add four short blasts to identify itself as a pilot.
➡ Interval: every ≤ 2 minutes.
➡ Audible range: 1–2 nm depending on size.
➡ Rule 35(j).

Question 25

What is the fog signal for a vessel at anchor?

Answer 25

➡ Rapid ringing of the bell for 5 seconds at intervals of ≤ 1 minute. ➡ Vessels ≥ 100 m: sound the bell forward + gong aft for 5 seconds each. ➡ May add one short, one prolonged, one short blast (to warn approaching vessels). ➡ Audible range: bell typically up to 0.5–1 nm, whistle up to 2 nm. ➡ Rule 35(g).

Question 26

What are the approximate audible ranges of fog signals by vessel size?

Answer 26

➡ Vessel ≥ 200 m – whistle designed for 2 nm audible range. ➡ Vessel 75–200 m – whistle designed for 1.5 nm audible range. ➡ Vessel < 75 m – whistle designed for 1 nm audible range. ➡ Bells/gongs – typically 0.5–1 nm. ➡ Rule reference: Annex III – Technical details of sound signal appliances.

Question 27

What is the fog signal for a vessel engaged in pilotage duty at anchor?

Answer 27

➡ Bell (anchor signal) + four short blasts on whistle to indicate pilot status. ➡ Interval: ≤ 1 min (bell), ≤ 2 min (whistle). ➡ Rule 35(j) in combination with 35(g).

Question 28

What is the fog signal for a vessel aground?

Answer 28

➡ Same as vessel at anchor: rapid bell (and gong if ≥ 100 m). ➡ Plus three distinct strokes of the bell immediately before and after the rapid ringing. ➡ May add one short, one prolonged, one short blast on whistle. ➡ Audible range: bell up to 0.5–1 nm, whistle 2 nm. ➡ Rule 35(h).

Question 29

What is the fog signal for a vessel less than 12 m?

Answer 29

➡ Not obliged to make the full signals. ➡ Must make some efficient sound signal at intervals ≤ 2 minutes (e.g., bell, whistle, horn). ➡ Audible range: usually < 1 nm. ➡ Rule 35(i).

Question 30

What lights does a vessel not under command (NUC) show?

Answer 30

➡ Two all-round red lights in a vertical line (unbroken 360°). ➡ When making way: also sidelights + sternlight. ➡ When at anchor: also anchor lights. Vertical separation: 1.5 m minimum if < 20 m; 2 m if ≥ 20 m. Rule reference: Rule 27(a).

Question 31

What lights does a fishing vessel (not trawling) show?

Answer 31

➡ Two all-round lights in a vertical line: Red over white. ➡ If gear > 150 m: all-round white light in direction of gear. ➡ Plus sidelights + sternlight when making way. Vertical separation: 1.5–2 m depending on vessel size. Rule reference: Rule 26(b).