What to check on a Navigation Lights.
Navigation lights are the fixed lights a vessel must show under the International Regulations for Preventing Collisions at Sea (COLREG) so that other vessels can judge its type, size, aspect and direction of travel at night or in restricted visibility. Each light — masthead, sidelights, sternlight, all-round, not-under-command, towing — has a defined arc of visibility in degrees and a minimum visibility range in nautical miles set by the vessel's length, not by a single fixed standard across all ships.
What this type is
Navigation lights are the fixed lights a vessel must show under the International Regulations for Preventing Collisions at Sea (COLREG) so that other vessels can judge its type, size, aspect and direction of travel at night or in restricted visibility. Each light — masthead, sidelights, sternlight, all-round, not-under-command, towing — has a defined arc of visibility in degrees and a minimum visibility range in nautical miles set by the vessel's length, not by a single fixed standard across all ships.
Main components
- Masthead light — white, forward arc of 225°, mounted on the centreline; larger vessels carry a second, higher masthead light aft of and higher than the forward one.
- Sidelights — red (port) and green (starboard), each covering 112.5° from dead ahead to abaft the beam.
- Sternlight — white, covering the 135° arc astern not covered by the sidelights.
- All-round light — visible over the full 360°, used for anchor lights, not-under-command signals, and on smaller craft that combine functions.
- Signal lights for special status — towing lights, not-under-command (two red all-round), restricted-in-ability-to-manoeuvre (red-white-red), fishing vessel lights, and similar COLREG-defined combinations.
Selection and sizing
| Vessel length | Masthead light range | Sidelight/sternlight range |
|---|---|---|
| Under 12m | 2 nm | 1 nm |
| 12-20m | 3 nm | 2 nm |
| 20-50m | 5 nm | 2 nm |
| 50m and over | 6 nm | 3 nm |
An LED retrofit must be selected against these COLREG Rule 22 ranges for the vessel's actual length, and the fixture's type approval certificate should state the range it meets, not just its power draw or lumen output.
Regulations and class
COLREG Rules 20 through 31 set the technical requirements for colour, arc and range; Annex I sets the detailed positioning and screening rules that stop one light's arc bleeding into a neighbouring sector. Fixtures must carry type approval evidencing compliance with these ranges and arcs, and class/flag surveys check the lights are the approved type, correctly positioned, and that the required indicator or alarm for light failure at the bridge is functioning.
Typical faults
- LED fixture swapped in without checking rated range — the light works but does not meet the visibility distance for the vessel's length.
- Screen or baffle damaged or missing, letting a sidelight's arc bleed across the bow and create a false aspect to an approaching vessel.
- Bridge failure-indicator lamp burnt out, so a navigation light outage goes unnoticed until reported from another vessel.
- Corrosion at the lamp housing seal admitting water, causing intermittent failure that is hard to reproduce during daytime testing.
What to look for in a supplier
- Type approval certificate stating the exact COLREG range and arc met, for the specific fixture model.
- Housing rated for the mounting location's vibration and weather exposure, not a generic marine rating.
- Compatibility with the existing bridge indicator/alarm panel wiring.
- LED driver quality — cheap drivers are a common early-failure point, not the LED itself.
Check navigation lights against their rated range at commissioning, not just for on/off state — a light that is lit but under-range is a COLREG deficiency that a night-time port state inspection will not accept.
