What vessels are telling you at night — and how misreading lights causes collisions
Contents
Use the links below to jump to any section:
- Why Navigation Lights Exist
- When Lights Must Be Displayed
- The Core Light Groups You Must Recognise Instantly
- Power-Driven Vessels Underway
- Power-Driven Vessels with Special Conditions
- Towing and Pushing Operations
- Fishing Vessels
- Vessels Restricted in Their Ability to Manoeuvre
- Vessels Constrained by Their Draught
- Sailing Vessels
- Anchored and Aground Vessels
- Pilot Vessels
- Small Craft and Incomplete Light Configurations
- Common Misidentifications and Traps
- Using Lights Together with Radar, AIS, and Bearing
- What to Do When the Lights Do Not Make Sense
1. Why Navigation Lights Exist
Navigation lights exist to answer three operational questions at night:
- What type of vessel is this?
- What is it doing right now?
- How constrained is its ability to manoeuvre?
They are not decorative, and they are not optional.
At night, lights are primary information, not confirmation of what radar already told you.
Many collisions occur because officers “waited for radar certainty” while the lights already showed the truth.
2. When Lights Must Be Displayed
Navigation lights must be shown:
- from sunset to sunrise
- during daylight in restricted visibility
- whenever deemed necessary to avoid collision
If a vessel is underway at night and not displaying proper lights, that is not your protection — it is your warning.
Rule 2 still applies.
3. The Core Light Groups You Must Recognise Instantly
Every watchkeeper must instantly recognise:
- sidelights (red / green)
- masthead lights
- sternlight
- all-round white lights
- all-round red and green lights
If you have to “count lights” slowly, you are already behind.
Recognition must be pattern-based, not analytical.
4. Power-Driven Vessels Underway
A power-driven vessel underway normally displays:
- one or two white masthead lights (depending on length)
- red and green sidelights
- a white sternlight
What this tells you operationally:
- the vessel has propulsion
- it is manoeuvrable
- COLREGs crossing, head-on, or overtaking rules apply
The relative movement of sidelights tells you aspect long before radar vectors stabilise.
5. Power-Driven Vessels with Special Conditions
Certain conditions modify the standard power-driven light pattern.
These are warnings, not trivia.
Examples include:
- vessels engaged in towing
- vessels with length-dependent masthead configurations
- vessels not under command
Each additional or altered light means reduced manoeuvring freedom or abnormal operation.
If you treat these as “still just a power-driven vessel,” you are ignoring critical information.
6. Towing and Pushing Operations
Towing vessels display additional masthead lights indicating tow length.
Operational reality:
- long tows cannot manoeuvre quickly
- course alterations may be limited
- the tow itself may be invisible on radar
Never pass close to a towing vessel simply because the tug appears small.
The lights are warning you about what you cannot see.
7. Fishing Vessels
Fishing vessels display all-round red and white lights indicating fishing operations.
Key mistake:
Assuming all fishing vessels are the same.
Fishing lights indicate:
- gear may extend far from the hull
- manoeuvrability may be severely limited
- course changes may not be possible
If you treat a fishing vessel like a normal power-driven vessel, you are likely to pass too close.
8. Vessels Restricted in Their Ability to Manoeuvre
These vessels display red-white-red all-round lights.
This is one of the most important light patterns at sea.
It means:
- the vessel cannot comply with COLREGs normally
- your manoeuvring options are greater than theirs
- you must keep well clear
Examples include dredging, cable-laying, underwater operations, or vessels recovering gear.
Failure to respect RAM lights is a frequent cause of collision and contact incidents.
9. Vessels Constrained by Their Draught
A vessel constrained by draught may display three all-round red lights in a vertical line.
This is not a “status symbol.”
It is a statement:
“I cannot safely deviate from my course.”
In narrow channels or traffic lanes, this light combination should immediately trigger early and decisive avoidance, not debate.
10. Sailing Vessels
Sailing vessels display:
- red and green sidelights
- a sternlight
- optional all-round red over green
Operational trap:
Assuming sailing vessels always behave predictably.
In practice:
- many sailboats have engines running
- lights may be misconfigured
- small craft may be poorly visible
Do not assume competence because a vessel is under sail.
11. Anchored and Aground Vessels
Anchored vessels show all-round white lights.
Aground vessels show:
- anchor lights
- plus two all-round red lights
Operational importance:
- anchored vessels may swing
- radar vectors may mislead
- background shore lights may mask them
Anchored vessels are common collision victims at night because officers underestimate drift and swing.
12. Pilot Vessels
Pilot vessels display white over red lights.
These vessels operate in high-risk traffic environments and often make unexpected manoeuvres.
They are not constrained, but they are busy.
Treat pilot vessels with margin and anticipation.
13. Small Craft and Incomplete Light Configurations
Small craft may display:
- reduced-range lights
- combined lanterns
- incorrect or incomplete configurations
This does not absolve you of responsibility.
Small craft are often:
- difficult to detect on radar
- poorly trained
- slow to react
Professional ships must compensate for this reality.
14. Common Misidentifications and Traps
Repeated night-time failure patterns include:
- confusing fishing vessels with tugs
- missing RAM indicators
- assuming a single white light is a small craft when it is actually a tow
- mistaking shore lights for vessels
- trusting AIS labels over visual lights
If lights and radar disagree, investigate immediately.
15. Using Lights Together with Radar, AIS, and Bearing
Lights should never be used in isolation.
A professional OOW cross-checks:
- visual lights
- radar bearing stability
- AIS data (with scepticism)
- charted traffic patterns
Lights give identity.
Radar gives movement.
Together they give intent.
16. What to Do When the Lights Do Not Make Sense
When lights appear contradictory or illogical:
- assume the other vessel may be wrong
- assume manoeuvrability may be limited
- increase CPA early
- reduce speed if necessary
- call the Master early in uncertainty
Confusion is not a reason to delay action.
It is a reason to create space.
Tags
COLREGs lights · navigation lights · night navigation · collision avoidance · bridge watchkeeping · vessel identification