33 CFR 62.45: Light characteristics of aids to navigation
Last reviewed: October 14, 2026
This section explains how lights on aids to navigation use color and rhythm to convey information. When proceeding in the Conventional Direction of Buoyage, green and red lights mark the sides of channels, and specific rhythms identify other kinds of marks. It also covers sector lights and reflective material.
Applies toLighted aids to navigation and aids to navigation fitted with light-reflecting material.
What it says
Lighthouses and range lights may display distinctive light characteristics to facilitate recognition, and no special significance should be attached to the color or rhythm of such lights.
33 CFR 62.45(a)“No special significance should be attached to the color or rhythm of such lights.”
When proceeding in the Conventional Direction of Buoyage, green lights mark port (left) sides of channels and locations of wrecks or obstructions to be passed by keeping the light on the vessel's port (left) hand.
33 CFR 62.45(b)(1)“Green lights mark port (left) sides of channels and locations of wrecks or obstructions which are to be passed by keeping these lights on the port (left) hand of a vessel.”
When proceeding in the Conventional Direction of Buoyage, red lights mark starboard (right) sides of channels and locations of wrecks or obstructions to be passed by keeping the light on the vessel's starboard (right) hand.
33 CFR 62.45(b)(2)“Red lights mark starboard (right) sides of channels and locations of wrecks or obstructions which are to be passed by keeping these lights on the starboard (right) hand of a vessel.”
Yellow lights have no lateral significance. White lights also have none, except on the Western Rivers, which the text refers to § 62.51.
33 CFR 62.45(c)“Yellow lights have no lateral significance. Except on the Western Rivers, see § 62.51, white lights have no lateral significance.”
Aids with lateral significance display regularly flashing or regularly occulting light rhythms, except as noted in § 62.51 for the Western Rivers.
33 CFR 62.45(d)(1)“Aids with lateral significance display regularly flashing or regularly occulting light rhythms.”
Safe Water Marks display a white Morse Code "A" rhythm (short-long flash), except as noted in § 62.51 for the Western Rivers.
33 CFR 62.45(d)(3)“Safe Water Marks display a white Morse Code “A” rhythm (short-long flash).”
Sector bearings are not precise, so mariners should consider sectors a warning only and should not use them to determine the exact bearing to the light.
33 CFR 62.45(e)“As sector bearings are not precise, they should be considered a warning only and not used to determine exact bearing to the light.”
Green or red reflective material is used only on marks which, if lighted, would exhibit a light of that color.
33 CFR 62.45(f)“Green or red reflective material is used only on marks which, if lighted, would exhibit a light of that color.”
Common questions
What does a green light on an aid to navigation mean?
When proceeding in the Conventional Direction of Buoyage, a green light marks the port (left) side of a channel or a wreck or obstruction to be passed with the light on the port hand. Green lights are also used on Preferred Channel Marks where the topmost band is green.
“Green lights are also used on Preferred Channel Marks where the topmost band is green.”
Do white or yellow lights have lateral significance?
Yellow lights have no lateral significance. White lights have none either, except on the Western Rivers, for which the text refers to § 62.51.
“Yellow lights have no lateral significance. Except on the Western Rivers, see § 62.51, white lights have no lateral significance.”
What light rhythm do Special Marks use?
Special Marks display yellow lights, with fixed or slow flashing rhythm preferred.
“Special Marks display yellow lights with fixed or slow flashing rhythm preferred.”
Can I use a sector light to get an exact bearing?
No. Sector bearings are not precise, so sectors should be considered a warning only.
“As sector bearings are not precise, they should be considered a warning only and not used to determine exact bearing to the light.”
The text of 33 CFR 62.45
Electronic Code of Federal Regulations (eCFR), current as of March 31, 2026 · Read it on eCFR
Light characteristics
(a) Lights on aids to navigation are differentiated by color and rhythm. Lighthouses and range lights may display distinctive light characteristics to facilitate recognition. No special significance should be attached to the color or rhythm of such lights. Other lighted aids to navigation employ light characteristics to convey additional information.
(b) When proceeding in the Conventional Direction of Buoyage, aids to navigation, if lighted, display light characteristics as follows:
(1) Green lights mark port (left) sides of channels and locations of wrecks or obstructions which are to be passed by keeping these lights on the port (left) hand of a vessel. Green lights are also used on Preferred Channel Marks where the topmost band is green.
(2) Red lights mark starboard (right) sides of channels and locations of wrecks or obstructions which are to be passed by keeping these lights on the starboard (right) hand of a vessel. Red lights are also used on Preferred Channel Marks where the topmost band is red.
(3) Certain lights marking the Intracoastal Waterway may display reversed lateral significance. See § 62.49.
(c) Yellow lights have no lateral significance. Except on the Western Rivers, see § 62.51, white lights have no lateral significance. The purpose of aids exhibiting white or yellow lights may be determined by their shape, color, letters or numbers, and the light rhythm employed.
(d) Light rhythms, except as noted in § 62.51 for the Western Rivers, are employed as follows:
(1) Aids with lateral significance display regularly flashing or regularly occulting light rhythms. Ordinarily, flashing lights (frequency not exceeding 30 flashes per minute) will be used.
(2) Preferred Channel Marks display a composite group flashing light rhythm (groups of two flashes followed by one flash).
(3) Safe Water Marks display a white Morse Code “A” rhythm (short-long flash).
(4) Isolated Danger Marks display a white group flashing two.
(5) Special Marks display yellow lights with fixed or slow flashing rhythm preferred.
(6) Mooring Buoys and Information and Regulatory Marks display white lights of various rhythms.
(7) For situations where lights require a distinct cautionary significance, as at sharp turns, sudden channel constrictions, wrecks, or obstructions, a quick flashing light rhythm (60 flashes per minute) may be used.
(e) Occasionally lights use sectors to mark shoals or warn mariners of other dangers. Lights so equipped show one color from most directions and a different color or colors over definite arcs of the horizon as indicated on the appropriate nautical chart. These sectors provide approximate bearing information since the observer should note a change of color as the boundary between the sectors is crossed. As sector bearings are not precise, they should be considered a warning only and not used to determine exact bearing to the light.
(f) Aids to navigation may be fitted with light-reflecting material to increase their visibility in darkness. Green or red reflective material is used only on marks which, if lighted, would exhibit a light of that color. Yellow reflective material is used on special marks and on Intracoastal Waterway marks. No significance is attached to white reflective material.
Sections it refers to
The plain-English explanation on this page was written with AI from the regulation text above and checked automatically before publishing: every quote appears in the text, every number comes from it, and a second model confirmed each statement adds nothing the text doesn't say. Regulation text current as of March 31, 2026. The regulation text governs. RegKnot is not affiliated with the U.S. Coast Guard.