USCG Navigation Rules: Right of Way, Signals, and Lights

The U.S. Coast Guard navigation rules are the federal rules of the road for vessels on American waters. They tell you who yields, how fast you can go, what lights and signals you have to show, and how a collision gets sorted out afterward. Two sets exist: the International Regulations for Preventing Collisions at Sea (COLREGs) apply offshore, and the U.S. Inland Navigation Rules in 33 CFR Part 83 apply inside the demarcation lines that run across harbor mouths, river entrances, and coastal inlets. The two systems share most of their content, but the differences — particularly in whistle signals — matter enough that operating under the wrong set can cause a collision or shift fault onto you.¹²

Figuring Out Which Set Applies

The demarcation lines are drawn in 33 CFR Part 80 and typically run across harbor mouths, river entrances, and the gaps between coastal inlets and open ocean. Cross one seaward and COLREGs govern. Cross it landward and Inland Rules take over. Most recreational boating on rivers, lakes, and inside bays happens under the Inland Rules. Coastal cruising, offshore fishing, and passages between ports usually mean COLREGs.

The Duties That Apply All the Time

Three foundational duties apply to every vessel, at every size, in every location.

Rule 5 requires a proper lookout by sight, hearing, and every available means, including radar and AIS if your vessel has them.³ After a collision, investigators look at whether a dedicated lookout was posted. Failure there almost guarantees a finding of fault.

Rule 6 requires safe speed. What counts as safe depends on visibility, traffic density, your stopping distance, sea state, wind, current, and water depth. A speed that’s fine on a clear afternoon in open water can be reckless in a crowded harbor at dusk. The test is whether you can stop or maneuver in time to avoid a collision given the conditions you’re actually in.

Rule 7 covers when a collision risk exists. If the compass bearing to an approaching vessel doesn’t change while the distance closes, a risk exists. When in doubt, assume it does.

Sitting above all of this is Rule 2, the General Prudential Rule. Two principles override everything else. Following the rules doesn’t excuse you from ordinary seamanship — if a precaution is needed and the rules don’t specifically mention it, you’re still responsible for taking it. And you’re allowed, sometimes required, to depart from the rules when doing so is the only way to avoid immediate danger.⁴ A captain who rigidly follows the crossing rules into an unavoidable collision isn’t being compliant; they’re being negligent.

Taking Action When a Collision Risk Exists

Once you’ve identified a collision risk, Rule 8 sets the standard. Any course or speed change must be large enough that the other vessel can see it, whether visually or on radar. Small, tentative adjustments — a degree or two at a time — create confusion and violate the rule. Move early, move obviously, and keep watching the other vessel until it’s past and clear. If maneuvering isn’t enough, slow down or stop.

Courts consistently treat half-measures taken too late as worse than no action at all, because they make your vessel unpredictable.

Who Yields to Whom

Head-On

When two power-driven vessels approach on roughly opposite courses and a collision risk exists, Rule 14 requires both to turn to starboard and pass port-side to port-side. Neither has priority. If there’s any doubt about whether a situation is head-on, treat it as one and turn to starboard.

Crossing

When two power-driven vessels cross paths, Rule 15 assigns clear roles. The vessel that sees the other on its starboard side is the give-way vessel and must act to avoid crossing ahead. The other is the stand-on vessel and holds its course and speed so the give-way vessel can predict its movements.³

One important inland exception: on the Great Lakes, Western Rivers, and certain other designated waters, a vessel crossing a river must yield to any vessel traveling up or down the river.² The current-driven vessel gets priority regardless of which side it’s on.

Overtaking

Rule 13 puts the full burden on the overtaking vessel. You are overtaking whenever you approach another vessel from a direction more than 22.5 degrees behind its beam, roughly from its stern quarter. Stay clear until you are completely past and well away. The obligation doesn’t shift even if your relative positions change during the maneuver.

When the Stand-On Vessel Must Act

Rule 17 tells the stand-on vessel to hold course and speed, but it also recognizes that sometimes the give-way vessel isn’t doing its job. If it becomes clear the give-way vessel isn’t taking action, the stand-on vessel may, and eventually must, take its own evasive action.

The Priority Hierarchy

Rule 18 creates a pecking order based on how easily each type of vessel can maneuver. When vessels of different categories meet, this hierarchy overrides the standard crossing and head-on rules. From highest priority to lowest:

Vessels not under command (unable to maneuver due to engine failure, steering breakdown, or similar exceptional circumstances).
Vessels restricted in their ability to maneuver (dredging, cable-laying, mine-clearing, and similar work).
Vessels engaged in fishing (commercial vessels actively working nets or trawls, not recreational anglers).
Sailing vessels (moving under wind power alone, no engine engaged).
Power-driven vessels.

International waters add a sixth category — vessels constrained by their draft — that doesn’t exist in the inland rules.³ The logic is simple: the vessel with the least ability to move gets the most protection.

Narrow Channels and Traffic Lanes

Rule 9 governs narrow channels and fairways, and it overrides Rule 18’s hierarchy in important ways. Every vessel moving through a narrow channel must keep as close to the starboard side as is safe and practical. Vessels under 20 meters and sailing vessels must not impede the passage of larger vessels that can only navigate safely within the channel. Fishing vessels can’t impede any vessel navigating the channel, regardless of size. Crossing traffic also has to stay clear.⁵

On the Great Lakes and Western Rivers, a power-driven vessel heading downbound with the current has right-of-way over upbound traffic and initiates the passing arrangement. At a blind bend, sound the appropriate signal and navigate with particular alertness.

Rule 10 governs traffic separation schemes — designated shipping lanes near busy ports and along congested coastlines. Travel in the appropriate lane in the direction of flow and stay clear of the separation zone. Join and leave at the ends of the lane where possible; if you must enter from the side, do it at a shallow angle. Avoid crossing a traffic lane, but when you have to, cross at as close to a right angle as practical.⁶

Restricted Visibility

Rule 19 replaces the normal crossing and head-on rules whenever you can’t see other vessels due to fog, heavy rain, snow, or similar conditions. Every vessel must slow to a safe speed for the conditions, and power-driven vessels must have their engines ready for immediate maneuvering.⁷

If you detect another vessel on radar alone and a close-quarters situation is developing, take avoiding action with plenty of time to spare. Two radar-based turns are restricted: don’t turn to port for a vessel forward of your beam (unless you’re overtaking), and don’t turn toward a vessel abeam or behind your beam.

If you hear a fog signal that sounds like it’s coming from ahead, or you can’t avoid a close-quarters situation with a vessel forward of your beam, reduce to the minimum speed needed to hold steerage. Stop entirely if you have to.

Sound and Whistle Signals

Sound signals are how vessels communicate intentions and warnings. Boats 12 meters or longer must carry a whistle, vessels 20 meters and up add a bell, and those 100 meters or longer also need a gong. Vessels under 12 meters need some effective means of making a sound signal but not this specific equipment.³

The most consequential difference between inland and international rules lives in these signals. On international waters, whistle blasts announce what a vessel is already doing: one short blast means “I am altering course to starboard,” and two short blasts means “I am altering course to port.”²

On inland waters, the signals are proposals, not announcements. One short blast means “I intend to leave you on my port side,” and two short blasts means “I intend to leave you on my starboard side.” The other vessel must return the same signal if they agree, creating a two-way arrangement before either vessel commits. If the other vessel doubts the safety of the proposal, they sound the danger signal instead.⁸

Three short blasts mean “I am operating in reverse” under both systems. Five or more short, rapid blasts is the universal danger signal — sound it immediately if you don’t understand what another vessel is doing or you think their proposed maneuver is unsafe. Inland Rule 34 also allows vessels to reach passing agreements by radiotelephone, in which case the whistle signals become optional; if no radio agreement is reached, whistle signals take over.

Navigation Lights and Day Shapes

Between sunset and sunrise, and during any period of restricted visibility, vessels display navigation lights that show their size, direction of travel, and status. A power-driven vessel underway shows a white masthead light forward, red and green sidelights (red on port, green on starboard), and a white stern light. Vessels 50 meters or longer add a second, higher masthead light aft.⁹

Sailing vessels show only sidelights and a stern light while under sail alone. Small power-driven vessels under 12 meters can substitute an all-round white light for the masthead and stern light. Vessels under 7 meters going 7 knots or less need only an all-round white light, with sidelights added if practical.

Reading other vessels’ lights: a red light means you’re looking at the port side. Green means starboard. Both red and green together means head-on. A lone white stern light means the vessel is moving away from you.

During daylight, vessels show black geometric day shapes to indicate their status:

Two balls in a vertical line — not under command.
Ball-diamond-ball vertically — restricted in ability to maneuver. Dredges add two balls on the obstruction side and two diamonds on the safe-passage side.
Two cones with points together — trawling.
One ball forward — at anchor.
Three balls in a vertical line — aground.
A downward-pointing cone forward — sailing vessel also using an engine.
A diamond — towing operation over 200 meters.

Recognizing these shapes from a distance tells you which Rule 18 category the vessel falls into, which decides who yields.

Distress Signals

Annex IV lists the recognized distress signals, and using any of them when you’re not actually in distress is prohibited.¹⁰ The most common are:

“Mayday” spoken by radiotelephone.
SOS transmitted by any signaling method in Morse Code (three short, three long, three short).
Red parachute or hand-held flares.
Orange smoke, mainly for daytime visibility.
Slowly and repeatedly raising and lowering outstretched arms.
A continuous sounding of any fog-signaling device.
EPIRB activation.
DSC distress alert on VHF Channel 70 or designated MF/HF frequencies.

An orange canvas panel marked with a black square and circle, or a dye marker in the water, serves as a visual signal to search aircraft.

Duty to Assist and Reporting an Accident

Federal law imposes a personal obligation on every vessel operator: if you encounter someone in danger of being lost at sea, you must render assistance as long as doing so won’t create serious danger to your own vessel or crew. Violating this duty carries up to $1,000 in fines, up to two years in prison, or both.¹¹

Marine casualties have to be reported to the Coast Guard. Under 46 U.S.C. § 6101, reportable casualties include any death, serious injury, significant property loss or damage affecting seaworthiness, and significant environmental harm. Written reports are due within five days. For commercial vessels, the property damage threshold that triggers immediate notice is $75,000.¹²

Recreational boating accidents follow a separate track through state authorities. A report is required when an accident causes death, injuries needing more than first aid, a person’s disappearance from the vessel, or property damage totaling $2,000 or more. Incidents involving death, serious injury, or disappearance must be reported within 48 hours. Other reportable accidents must be reported within 10 days.¹³ Failing to report as required can bring a civil penalty of up to $25,000.¹⁴

What Breaking the Rules Costs

Violating any provision of the Inland Navigation Rules carries a civil penalty of up to $18,610 per violation under 33 U.S.C. § 2072, adjusted for inflation. The penalty can be assessed against both the operator and the vessel for the same incident.¹⁵

Operating a vessel negligently so as to endanger life, limb, or property triggers additional penalties under 46 U.S.C. § 2302: up to $5,000 for recreational vessels or $25,000 for commercial vessels. Grossly negligent operation is a federal misdemeanor. If gross negligence causes serious bodily injury, it becomes a felony and carries an additional civil penalty of up to $35,000.¹⁶

The bigger consequence often isn’t the fine. A navigation rule violation that contributes to a collision creates a strong presumption of fault in civil liability. Admiralty courts have long held that when a vessel breaks a rule and a collision follows, the burden shifts to that vessel to prove the violation didn’t cause the accident. In practice, that burden is nearly impossible to carry.

1
United States Coast Guard. COLREGS vs INLAND Waters
2
Navigation Center. USCG Amalgamated Navigation Rules International and U.S. Inland
3
eCFR. 33 CFR Part 83 – Navigation Rules
4
eCFR. 33 CFR 83.02 – Responsibility (Rule 2)
5
eCFR. 33 CFR 83.09 – Narrow Channels (Rule 9)
6
eCFR. 33 CFR 83.10 – Rule 10, Traffic Separation Schemes
7
eCFR. 33 CFR 83.19 – Conduct of Vessels in Restricted Visibility (Rule 19)
8
eCFR. 33 CFR 83.34 – Maneuvering and Warning Signals (Rule 34)
9
eCFR. 33 CFR Part 83 Subpart C – Lights and Shapes
10
Navigation Center. ANNEX IV: International Distress Signals
11
Office of the Law Revision Counsel. 46 U.S. Code 2304 – Duty to Provide Assistance at Sea
12
Office of the Law Revision Counsel. 46 U.S. Code 6101 – Marine Casualties and Reporting
13
United States Coast Guard Boating Safety. Accident Reporting
14
Office of the Law Revision Counsel. 46 U.S. Code Chapter 61 – Reporting Marine Casualties
15
eCFR. 33 CFR 27.3 – Penalty Adjustment Table
16
Office of the Law Revision Counsel. 46 U.S. Code 2302 – Penalties for Negligent Operations and Interfering With Safe Operation