Hide Ships at Night (Blackout Light Protocols)
A vessel should not switch off, dim, or cover required navigation lights to avoid being seen. COLREGs require prescribed lights from sunset to sunrise and during restricted visibility. Safe night operations begin by confirming the vessel’s status, route, and applicable rules, then checking that approved lights work, meet required visibility ranges, and remain unobstructed.
Imagine planning a night passage and seeing bright deck lights reflect off the water. It may seem sensible to reduce the vessel’s visible light, but changing required navigation lights can make the vessel’s direction and status harder for others to judge. The safer response is to identify which lights are required, remove interference from optional lighting, and confirm that the approved lights are working.
The term “blackout” can mean different things in different settings. For navigation, it must not be treated as permission to hide a vessel by disabling, masking, or dimming required lights. This guide explains a compliant approach based on COLREGs Rules 20–22, while noting that vessel type, flag-state rules, port requirements, and operating conditions can affect the full configuration.
Planning: Vessel Status, Route, and Applicable Rules
Planning means establishing which navigation lights the vessel must show before departure. The correct configuration depends on the vessel’s length, category, activity, and status, as well as applicable international, flag-state, and local requirements. Start with the rules for the actual voyage, not a generic “night mode.”
COLREG Rule 20 sets when prescribed lights must be shown: from sunset to sunrise, and during periods of restricted visibility. It also requires lights not to be obscured by other lights or structures. Rules 21 and 22 define light types and required visibility ranges, but those ranges alone do not determine every vessel’s complete light configuration.
Before a passage, confirm:
- The vessel’s length and category.
- Its activity and status, such as whether it is underway or engaged in another operation covered by the rules.
- The route, expected visibility, and any port or local requirements.
- The flag-state rules and the vessel’s approved light plan.
- Whether any planned work or deck lighting could interfere with required lights or the lookout.
A vessel that is alongside, underway, towing, or engaged in a particular activity may have different requirements. Do not infer the required configuration from vessel size alone. Check the applicable rules and the vessel’s operating documents; when the situation is unclear, seek guidance from the responsible authority or a qualified maritime professional before sailing.
Key takeaway: Set the light plan from vessel status and rules first. Do not use a broad blackout instruction in place of that check.
Access and Clearances: Light Arcs and Unobstructed Sightlines
A light’s visibility arc is the direction over which it is designed to be seen. Keeping the required arcs clear allows other vessels to interpret the lights. Inspect for physical obstructions and for other lights that could confuse or wash out the required signals.
Rule 20 says prescribed lights must not be obscured by structures or other lights. In practical terms, a new fitting, stored gear, temporary cover, or bright work light may create a problem even if the navigation light itself is in working order. Look at the installation from the directions that matter, using the vessel’s approved arrangement rather than guessing at an angle.
Review the vessel with these questions:
- Is each required light securely fitted and free of a cover or obstruction?
- Could cargo, equipment, a canopy, or another structure block its designed arc?
- Could decorative, cabin, or work lighting make a required light harder to distinguish?
- Can the watchkeeper see the vessel’s surroundings without glare that impairs lookout?
- Has any recent repair or equipment change altered the light’s position or view?
If another light interferes, address the source of interference only in a way that preserves safe operations and applicable requirements. Do not improvise a screen, alter a light’s output, or move equipment in a way that masks a required signal. If you cannot confirm the approved arrangement, consult the vessel’s documentation or a qualified technician.
Key takeaway: Check sightlines and glare from more than one direction. A working lamp can still be ineffective if something blocks or confuses its signal.
Required Visibility Ranges: What the Numbers Mean
Rule 22 gives minimum visibility ranges for specified navigation lights. A nautical mile (NM) is the unit used here. These figures are minimum requirements, not targets for reducing light output, and they do not authorize masking or switching off a required light.
| Vessel length | Masthead light minimum range | Sidelight minimum range | Sternlight minimum range |
|---|---|---|---|
| 50 m or more | 6 NM | 3 NM | 3 NM |
| 12 m to under 50 m | 5 NM | 2 NM | 2 NM |
| Under 12 m | 2 NM | 1 NM | 2 NM |
Use the table as a threshold reference for the listed light types. The applicable light configuration still depends on vessel category, activity, and status. Other lights have their own requirements, and a vessel may need additional lights under the rules. A range value does not say which lights to show in a particular situation.
The ranges also do not mean a light is safe to obscure because it might still be visible at shorter distances. They are minimum required visibility ranges. If a light is damaged, poorly powered, blocked, or otherwise not functioning as intended, record the defect and resolve it before departure in line with applicable requirements.
Key takeaway: Apply the correct row for vessel length, then verify the entire required configuration separately. Never treat the minimum range as permission to dim or mask a light.
Execution: Approved Light Configuration and Pre-Departure Checks
Execution means operating only the lights required for the vessel’s status and activity, while keeping them unobstructed and maintaining a proper lookout. Use approved equipment and the vessel’s established procedures. Do not create a “dark” setting that disables required navigation lights.
A practical pre-departure sequence is:
- Confirm the plan. Recheck vessel status, route, visibility conditions, and applicable flag-state and port rules.
- Identify required lights. Use the vessel’s approved light plan and the relevant COLREG requirements. Do not rely on a generic checklist when the vessel’s activity changes.
- Inspect the fittings. Look for damage, loose connections, contamination, covers, or nearby items that obstruct the designed view.
- Test operation. Follow the equipment maker’s instructions or vessel procedure. Confirm the required lights operate as intended; do not use an improvised test that could damage equipment or create risk.
- Check for interference. With safe conditions and a suitable view, confirm that optional lighting does not obscure or confuse required lights.
- Record defects. Note failures and report them through the vessel’s maintenance or safety process before sailing.
Lighting needs may change as vessel status or conditions change. The watch should follow the applicable requirements throughout the operation, not just at the start of a voyage. A light check is also not a substitute for maintaining a proper lookout.
If a required light fails, do not assume that a spare, an optional lamp, or a reduced-light arrangement is an acceptable substitute. Follow the vessel’s defect procedure and the rules of the competent authority. Do not proceed at night or in restricted visibility with required lights inoperative unless the authority’s rules permit a safe alternative.
Key takeaway: Check, test, and document before departure. If a required light is defective, resolve the issue or get authoritative direction before proceeding.
Verification: Functional Tests, Defects, and Operating Records
Verification is evidence that the required lights work and remain usable for the planned operation. It combines a functional check with a review of obstructions, interference, and records. A switch position alone does not prove that a light is visible or operating correctly.
Follow the equipment-specific test procedure. Depending on the installation, that may include checking controls, power supply, and visible operation. Do not assume every system has the same indicator or test method. If a lamp does not operate, behaves inconsistently, or appears obstructed, treat it as a defect and report it.
A useful record can include:
- Date and time of the check.
- Vessel and light positions checked.
- Results and any defect found.
- Action taken, person notified, and follow-up required.
- Any change to the planned operation due to the defect.
Illustrative scenario 1: New deck lighting. A crew adds work lights for a night task. During the check, they find that the added light makes a required navigation light harder to distinguish. The compliant response is to reassess or control the interfering work light as appropriate, preserve required signals, and maintain the lookout, rather than cover or dim the navigation light.
Illustrative scenario 2: A failed light before departure. A pre-departure check finds a required light is not operating. The crew records and reports the fault, then follows the vessel’s maintenance process and applicable authority guidance. They do not treat the remaining lights as a substitute unless an authorized safe alternative applies.
These are examples, not accounts of specific incidents. Their common lesson is that a pre-departure check can reveal problems before they become hazards. Records also help the crew track repeated faults and confirm that reported issues receive follow-up.
Key takeaway: Verify actual operation, not just the control setting. Record defects and confirm that corrective action is complete.
Choosing a Safe Response to Night-Light Concerns
The right response depends on what is causing concern. Reducing glare, addressing a faulty fitting, and responding to a vessel’s required signal are different tasks. The comparison below keeps those decisions focused on compliance and safe navigation.
| Situation | Safe next step | Avoid |
|---|---|---|
| Optional work light causes glare | Review the work-light setup while preserving required lights and lookout | Covering or dimming a required navigation light |
| A required light appears blocked | Inspect the obstruction and restore the approved clear view | Installing an improvised screen |
| A navigation light fails its check | Record and report the fault; follow authority and vessel procedures | Sailing as if another light automatically replaces it |
| Vessel status or required configuration is uncertain | Check the approved plan and applicable rules; seek qualified guidance | Guessing from length alone |
| Restricted visibility occurs | Follow applicable light and lookout requirements | Switching off lights to reduce visibility |
A “blackout” order is not, by itself, a compliance plan. If an operation calls for reduced nonessential lighting, first identify which lights are required and ensure the change does not impair signals or lookout. The obligation to show required lights remains central.
Key takeaway: Manage glare and equipment problems without concealing required signals. When the rules or a defect leave doubt, pause and get competent guidance.
FAQ
These answers summarize the core points for routine planning. They do not replace the rules that apply to a specific vessel, activity, or port. When circumstances differ from a standard passage, check the vessel’s approved procedures and seek authoritative advice.
Can a vessel switch off navigation lights to avoid being seen?
No. Required lights must be shown under applicable rules. Switching them off can hide the vessel’s status and movement from other traffic and create collision risk.
When must prescribed navigation lights be shown?
COLREG Rule 20 requires them from sunset to sunrise and during periods of restricted visibility. Other circumstances and vessel-specific requirements may also apply.
Do Rule 22 visibility ranges tell me which lights to show?
No. Rule 22 specifies minimum ranges for listed lights. The full configuration depends on the vessel’s category, length, activity, and status.
What is the minimum masthead-light range for a vessel under 12 m?
The Rule 22 minimum is 2 NM. Confirm the vessel’s full light requirements separately.
Can I dim a required light if it seems too bright?
Do not dim or alter a required light unless an applicable rule and approved procedure allow it. Check for glare or interference from optional lighting instead.
Can deck or work lights remain on at night?
They must not obscure or confuse prescribed lights or impair the lookout. Review their use in the context of the operation and applicable rules.
What should I do if a required light fails before departure?
Record and report the defect, then follow the vessel’s maintenance process and competent authority’s rules. Do not assume another lamp is an authorized replacement.
Are the visibility ranges the same for every vessel?
No. The listed minimums vary by vessel length and light type. Vessel category, activity, flag-state rules, and local requirements may affect what else is required.
What is the safest first step when the light configuration is unclear?
Confirm the vessel’s status and consult its approved light plan and applicable rules. If uncertainty remains, ask the responsible authority or a qualified maritime professional before proceeding.
(This article was written by one of our staff writers, Steven Langford. Visit our Meet the Team page.)
