The operator of a stand-on vessel should maintain course and speed. That is your primary obligation: keep doing exactly what you’re doing so the give-way vessel can predict your movements and navigate around you. But this duty isn’t absolute. If the give-way vessel fails to act, you have a responsibility to take avoiding action yourself, and the rules spell out exactly when that shift happens.
Why Holding Course and Speed Matters
Navigation rules work because they make boats predictable. When two vessels are on a collision course, one is designated the give-way vessel (required to alter course or speed to stay clear) and the other is the stand-on vessel. The stand-on vessel’s job is straightforward: don’t change anything. Keep your heading. Keep your throttle where it is. The give-way vessel needs a stable target to maneuver around, and if you start making unpredictable moves, you risk turning a manageable situation into a dangerous one.
The give-way vessel is required to take “early and substantial action” to keep well clear. That language is intentional. They shouldn’t wait until the last minute, and their course change should be obvious enough that you can see it happening.
How to Tell If a Collision Risk Exists
Before any of these rules come into play, you need to determine whether a collision risk actually exists. The key technique is checking the compass bearing of the approaching vessel. If that bearing stays roughly the same while the distance between you shrinks, you’re on a collision course. This is sometimes called “constant bearing, decreasing range,” and it’s one of the most reliable indicators of danger on the water.
If there’s any doubt about whether a collision risk exists, treat it as though it does. The navigation rules are explicit on this point: doubt equals risk. Don’t make assumptions based on limited information, and use radar if you have it.
The Two Stages of Escalation
Your obligations as a stand-on vessel shift through two distinct stages, and understanding the difference between them is critical.
Stage One: You May Act
If it becomes apparent that the give-way vessel is not taking appropriate action, you are permitted to maneuver on your own to avoid collision. This is the “may act” stage. Maybe the other vessel hasn’t changed course. Maybe it’s still bearing down on you with no sign of altering speed. At this point, you’re no longer locked into holding course and speed. You have the option to take evasive action yourself.
Stage Two: You Must Act
If the situation deteriorates to the point where collision cannot be avoided by the give-way vessel alone, your obligation changes from optional to mandatory. You shall take whatever action best helps avoid a collision. At this stage, standing on is no longer an option. You are legally required to act, and waiting any longer could make you partially at fault in an accident.
The difference between “may” and “shall” in these rules carries real legal weight. A stand-on vessel that rigidly holds course and speed all the way into a collision, insisting on its right of way, can be found liable for failing to take action when it became necessary.
How to Maneuver If You Must Act
When you do take evasive action, one important restriction applies: in a crossing situation between two power-driven vessels, you should not turn to port (left) if the other vessel is on your port side. Turning toward the give-way vessel or crossing in front of it creates exactly the kind of unpredictability that causes collisions. A turn to starboard or a speed reduction is generally the safer choice.
Make your maneuver decisive and visible. A slight course adjustment may not be noticeable to the other operator, especially at a distance. The goal is to make your intentions unmistakable.
Using Sound Signals
If you’re unsure what the other vessel is doing, or if its course looks dangerous, sound the danger signal: five or more short, rapid blasts on your horn. This signal communicates that you don’t understand the other vessel’s intentions or that you believe its current path is unsafe. Both vessels should then take appropriate action until a safe passing arrangement is clear.
Which Vessel Is the Stand-On Vessel?
The stand-on and give-way roles depend on the type of encounter and the types of vessels involved. In a crossing situation between two powerboats, the vessel with the other on its starboard (right) side is the give-way vessel. In an overtaking situation, the vessel doing the overtaking always gives way, regardless of vessel type.
Beyond these situational rules, there’s a general hierarchy based on maneuverability. Vessels that are harder to maneuver get priority. From highest priority to lowest:
- Vessels not under command (broken down, unable to maneuver)
- Vessels restricted in their ability to maneuver (dredging, towing, laying cable)
- Vessels engaged in fishing (with nets or trawls deployed, not just trolling a line)
- Sailing vessels (under sail only, no engine)
- Power-driven vessels
A powerboat gives way to all of the above. A sailboat gives way to fishing vessels, restricted vessels, and vessels not under command. This hierarchy can be overridden in specific situations like narrow channels or traffic separation schemes, but it covers most encounters on open water.
Identifying Vessels at Night
At night, you determine what another vessel is doing by reading its navigation lights. Every vessel displays a red light on its port (left) side and a green light on its starboard (right) side. If you see only a green sidelight, you’re looking at the other vessel’s starboard side, which typically means you’re the stand-on vessel in a crossing situation. If you see only a red sidelight, you’re seeing its port side, and you’re likely the give-way vessel. Seeing both red and green together, along with a white masthead light, means the vessel is heading roughly toward you.
Knowing how to read these lights quickly is essential, because at night you have less time and fewer visual cues to assess the situation. The same rules about bearing and range apply: if the lights aren’t shifting position relative to your boat, you’re on a collision course.