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Quizzes > Lifestyle & Hobbies

Navigation Lights Quiz: Practice COLREGs Light Patterns

Quick, free COLREGs lights quiz with real-world scenarios. Instant results.

Editorial: Review CompletedCreated By: Arup BarikUpdated Aug 28, 2025
Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art illustration for maritime light regulations quiz on teal background

This navigation lights quiz helps you spot the correct COLREGs lights for common vessels and situations. Answer quick, practical questions and get instant feedback to fix gaps before an exam or your next trip on the water. For more signal practice, try our traffic light test, explore a lighting quiz, or build fundamentals with a led basics quiz.

What color is the port sidelight on a power-driven vessel?
White
Green
Yellow
Red
The port sidelight is always red and is displayed on the vessel's left side. It shows an unbroken arc of 112.5° from directly ahead to 22.5° abaft the beam, enabling other vessels to determine your orientation and avoid collisions. This color convention is universal under COLREGS.
What is the minimum visibility range required for a vessel's masthead light if the vessel is less than 50 meters in length?
2 nautical miles
3 nautical miles
5 nautical miles
4 nautical miles
A vessel under 50 meters must exhibit a masthead light visible at a minimum of 3 nautical miles. Larger vessels require greater visibility distances to ensure other vessels can spot them at night or in low visibility. This requirement helps maintain safe separation at sea.
What is the horizontal arc of visibility for a vessel's sidelights?
180°
135°
90°
112.5°
Each sidelight (port and starboard) shows an arc of 112.5° from dead ahead to 22.5° abaft the beam. This specific arc ensures other vessels can identify the side of approach. Consistency in these arcs is crucial for collision avoidance.
When at anchor in open waters, what lights must a vessel display?
Flashing yellow light
Red over green sidelights
A white sternlight only
One all-round white light at the fore and one at the stern
A vessel at anchor must exhibit an all-round white light at the fore and, if over 50 meters, another at the stern so as to be visible to other vessels. Smaller vessels under 50 meters may display a single all-round white light. These anchor lights indicate that the vessel is stationary.
What color is the starboard sidelight on a power-driven vessel?
Red
Yellow
White
Green
The starboard sidelight is always green and is displayed on the vessel's right side. It shows an arc of 112.5° from dead ahead to 22.5° abaft the beam on the starboard side. This standard color coding helps mariners determine the orientation and direction of other vessels.
Which light pattern identifies a vessel that is not under command?
Two red all-round lights in a vertical line
Two green all-round lights in a vertical line
Red over white in a vertical line
Red over green in a vertical line
A vessel not under command must exhibit two all-round red lights in a vertical line where they can best be seen. This indicates the vessel is unable to maneuver and other vessels must give way. It's a critical signal to avoid collisions if the vessel cannot maintain course or speed.
Which statement describes the sternlight on a power-driven vessel?
A white light showing an arc of 180°
A white light showing an arc of 135° centered on the stern
A green light showing an arc of 112.5°
A red light showing an arc of 135°
The sternlight is a white light placed as nearly as practicable at the stern that shows an unbroken arc of 135°, 67.5° on each side of dead astern. This allows vessels astern to see that you are going away from them. The color and arc are standardized in COLREGS.
A sailing vessel underway under sail alone must exhibit which lights?
A single white all-round light
Flashing yellow light
A masthead light and sidelights
Red and green sidelights and a white sternlight
Under sail alone, a sailing vessel displays red and green sidelights and a white sternlight. It does not exhibit a masthead light while sailing. This configuration distinguishes it from power-driven vessels.
What color is an all-round light when used as an anchor light?
Yellow
Red
Green
White
An anchor light is always a white all-round light. It must be visible 360° around the horizon to inform other vessels that you are stationary. Using any other color would confuse your status at anchor.
What is the required visibility range for an anchor light on a vessel less than 50 meters in length?
1 nautical mile
2 nautical miles
4 nautical miles
3 nautical miles
A vessel less than 50 meters in length must exhibit an all-round white anchor light visible at 2 nautical miles. Larger vessels require greater visibility distances. This ensures nearby vessels can spot anchored vessels at night.
What is the horizontal arc of visibility of a vessel's masthead light?
112.5°
225°
180°
135°
The masthead light shows an unbroken arc of 225° from right ahead to 22.5° abaft the beam on both sides. This wide arc ensures vessels approaching from ahead and broad on each side can see your vessel's orientation at night.
How many masthead lights must a vessel over 50 meters but under 100 meters in length display at night?
One
Two
Three
None
A vessel over 50 meters but under 100 meters must exhibit two masthead lights in a vertical line. Larger vessels over 100 meters require three masthead lights. This helps indicate the vessel's size and towing status.
Which lights must a sailing vessel under sail alone exhibit at night?
All-round white light only
Red and green sidelights plus white sternlight
Masthead light, sidelights, and sternlight
Flashing yellow light only
Under sail alone, a sailing vessel displays only sidelights (red and green) and a sternlight. It does not carry a masthead light, which distinguishes it from power-driven vessels.
A vessel engaged in trawling at night must exhibit which light configuration?
White over green over white in a vertical line
Red over white over red in a vertical line
Green over white over green in a vertical line
Green over red over green in a vertical line
A vessel trawling shows two all-round green lights with a single all-round white light between and below them in a vertical line. This indicates the vessel's fishing activity and its direction of trawl. Other fishing vessels use different configurations.
What additional light may a vessel engaged in dredging or underwater operations exhibit?
A special flashing yellow light
A quick-flashing white light
A continuous red light
A flashing green light
In addition to the lights required by COLREGS, vessels engaged in dredging or underwater operations may exhibit a special flashing yellow light to warn others of the nature of their work and the need for extra caution. This yellow light is distinct from standard navigation lights.
A vessel at anchor over 50 meters in length must display how many all-round white lights?
Three
None
One
Two
Vessels over 50 meters at anchor must exhibit two all-round white lights in a vertical line: one at the forward position and one at the stern. Smaller vessels may use a single light. This ensures visibility from both ends of the vessel.
Which characteristic distinguishes a flashing light under COLREGS?
Equal durations of light and darkness
Darkness duration is shorter than the duration of light
Continuous light with brief eclipses
Light duration is shorter than the duration of darkness
A flashing light is defined as one in which the total duration of light in each period is shorter than the total duration of darkness, making it easily distinguishable from fixed and other lights. This helps mariners identify special signals and warnings.
What is the required visibility range for sidelights on vessels of any size?
2 nautical miles
3 nautical miles
1 nautical mile
4 nautical miles
All sidelights, regardless of vessel size, must be visible for at least 2 nautical miles. This consistency ensures predictable recognition of a vessel's side lights by others at sea.
What color is the sternlight on a power-driven vessel?
White
Red
Green
Yellow
The sternlight is always white and is placed as nearly as practicable at the stern. It shows an unbroken arc of 135°, allowing vessels astern to see you. This white color distinguishes it from sidelights.
Which of these vessels is not required to exhibit a masthead light?
A towing vessel
A pilot vessel underway
A sailing vessel under sail alone
A power-driven vessel
A sailing vessel under sail alone does not exhibit a masthead light, whereas power-driven, towing, and pilot vessels must display one or more masthead lights. This distinction helps other mariners identify whether a vessel is being propelled by sail or engine.
A pilot vessel on duty underway shall exhibit which all-round lights in a vertical line?
White over green over white
White over red over white
Red over white over red
Green over white over green
Under COLREGS Rule 21(d)(ii), a pilot vessel underway displays an all-round white light, then an all-round red light, and another all-round white light in a vertical line. This distinctive pattern signals pilot duty.
Which lights indicate a vessel constrained by its draft?
White over red over white
Three green all-round lights in a vertical line
Three red all-round lights in a vertical line
Red over white over red
A vessel constrained by her draft must exhibit three all-round red lights in a vertical line where they can best be seen. This signals limited maneuverability due to her draft.
A vessel engaged in mine clearance displays which all-round lights at night?
Three green all-round lights in a vertical line
White over green over white
Red over white over red
Green over white over green
Mine clearance vessels under COLREGS Rule 27(b) exhibit three all-round green lights in a vertical line where they can best be seen. This unique signal warns other vessels to keep clear.
Which lights must a vessel engaged in dredging or underwater operations exhibit, beyond standard navigation lights?
Three all-round yellow lights in a vertical line
Red over white over red
White over red over white
Two all-round red and two all-round green lights in a vertical line
Dredging or underwater operations under Rule 27(a)(i) require vessels to show two all-round green lights in a vertical line on the side where safe passing is permitted and two all-round red lights on the side where it is not. This warns others of the operation's extent.
A vessel towing another astern with a tow exceeding 200 meters must exhibit how many white masthead lights in a vertical line?
One
Three
None
Two
Under Rule 24(b)(i), a towing vessel with a tow exceeding 200 meters must exhibit three all-round white masthead lights in a vertical line. This indicates a long tow and helps other vessels assess passing clearances.
Which lights identify a vessel being towed astern at night?
No lights
The sidelights and sternlight of the towed vessel
A single white all-round light
Red over green all-round lights
A vessel being towed astern shows its own sidelights and sternlight, enabling other vessels to see the tow's extent and navigate safely around it. The towing vessel also shows appropriate tow lights.
How is a vessel pushing ahead and alongside another vessel identified by lights?
No special lights beyond power-driven vessel lights
Three masthead lights
One masthead light and one red light
Two all-round white masthead lights in a vertical line on the bow unit
When vessels are pushed ahead or alongside, the unit in control exhibits two all-round white masthead lights in a vertical line at the forward-most point, signifying it as a power-driven unit. Other standard lights are also shown.
Which additional lights must a vessel not under command exhibit when underway at night?
Three white masthead lights
Two all-round red lights in a vertical line plus sidelights and sternlight
Two all-round green lights in a vertical line plus sidelights and sternlight
Red over white over red plus sidelights and sternlight
A vessel not under command underway shows two all-round red lights in a vertical line to indicate its lack of maneuverability, and it must also display sidelights and a sternlight if making way.
Which lights, in addition to anchor lights, must a vessel aground display at night?
Two all-round red lights in a vertical line
Green over white over green
Three all-round red lights in a vertical line
White over red over white
In addition to its anchor lights, a vessel aground must exhibit two all-round red lights in a vertical line where they can best be seen, indicating its grounded status to other vessels.
What is the minimum vertical separation required between two masthead lights on a vessel over 50 meters in length?
2 meters
0.5 meter
1.5 meters
1 meter
COLREGS Rule 21 states that when two masthead lights are required, they must be placed in a vertical line at least 1 meter apart to ensure distinct visibility. Proper spacing prevents overlapping of the light arcs.
A vessel of 130 meters in length must exhibit a masthead light visible for at least how many nautical miles?
6 nautical miles
5 nautical miles
3 nautical miles
4 nautical miles
Vessels over 100 meters must exhibit a masthead light with a visibility range of at least 6 nautical miles under COLREGS Rule 21(a). This extended range enhances early detection by other vessels.
A special flashing light under COLREGS is defined by its flash rate. What is the minimum number of flashes per minute for a special flashing light?
50 flashes per minute
90 flashes per minute
70 flashes per minute
30 flashes per minute
A special flashing light is required to flash at a minimum of 50 times per minute so it is clearly distinguishable from other navigation lights, according to Annex I of COLREGS. This frequency ensures it is recognized as a special signal.
What is the arc of visibility for an all-round light?
135°
360°
225°
180°
An all-round light shows an unbroken arc of 360° around the horizon, making it visible from any direction. This characteristic distinguishes all-round lights from directional lights like sidelights or masthead lights.
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Study Outcomes

  1. Identify Navigation Light Configurations -

    Recognize the specific colors, placements, and characteristics of vessel navigation lights to correctly answer questions in our nav rules practice test.

  2. Apply Nav Lights Regulations -

    Interpret international nav lights regulations to determine compliance requirements for different vessel types and operating conditions.

  3. Interpret Light Signal Meanings -

    Analyze various light signals to understand right-of-way, vessel status, and safe sailing protocols during our navigation rules quiz.

  4. Differentiate Operational Scenarios -

    Distinguish between navigation light requirements for power-driven, sailing, and anchored vessels under daytime and nighttime conditions.

  5. Evaluate Compliance Strategies -

    Assess real-world situations to ensure correct nav lights are displayed, reinforcing best practices before taking the maritime navigation practice test.

  6. Prepare for the Nav Rules Practice Test -

    Employ test-taking strategies and focused review techniques to boost your confidence and accuracy on the vessel navigation lights quiz.

Cheat Sheet

  1. COLREG Color Sectors -

    Under Rule 21 of the International Regulations for Preventing Collisions at Sea (COLREGs), port-side lights display red over an arc of 112.5°, starboard-side lights display green over 112.5°, and a white stern light covers 135°. Memorize "Red on Port, Green on Starboard, White on the Stern" to ensure you can identify vessel headings at night.

  2. Geographic Range Formula -

    The maximum distance at which a light is visible depends on the height of the light above water: d = 2.08 × (√h₝ + √h₂) nautical miles, where h₝ and h₂ are the heights in meters of observer eye and masthead. For example, a masthead light 9 m high seen by an observer 4 m above water yields d ≈ 2.08 × (3 + 2) ≈ 10.4 NM.

  3. Nominal Range & Luminous Intensity -

    Nominal range refers to the distance a light is seen in standard atmospheric conditions and is determined by luminous intensity using the inverse-square law E = I/r², where E is illuminance, I is intensity in candelas, and r is distance in meters. IMO Resolution A.227 charts help match intensity to nominal range - for instance, 25 cd for a 2 NM visibility.

  4. Vessel Lighting Configurations -

    COLREG Rule 23 requires vessels under 50 m to show a single masthead light and those 50 m or more two masthead lights in a vertical line. Boats under 12 m may combine sidelights and stern light into one lantern. Always consult U.S. Coast Guard Nav Rules publications for specific vessel-length adaptations.

  5. Anchoring & All-Round Lights -

    When at anchor in open water, vessels under 50 m must display an all-round white light visible at 2 NM; vessels 50 m or more show two all-round whites - one forward and one aft. Rule 30(b) of the COLREGs specifies these requirements to prevent collisions in restricted visibility.

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