When the stand-on vessel may act to avoid a collision if the give-way vessel doesn't take early and substantial action.

Stand-on, Give-way, and the moment to act: a practical guide to COLREGs Rules of the Road

If you’ve ever found yourself on a small vessel watching two ships creep closer in a narrow channel, you’ve felt the tension between staying the course and staying safe. The Rules of the Road aren’t just abstract guidelines; they’re real-world instructions that save lives. And one of the trickier questions mariners wrestle with is this: when exactly can the stand-on vessel take action to avoid a collision?

Let’s unpack it in plain language, with a few real-world perspectives. The short answer is simple, but the implications are nuanced: the stand-on vessel may act to avoid a collision when the give-way vessel does not take early and substantial action to avoid danger. Now, what does that actually mean on deck, at the helm, or in the conning station? Here’s how it all fits together.

Stand-on vs. give-way: who has the duty, and why it matters

• Stand-on vessel: This boat or ship has the right of way and should maintain its course and speed to keep a predictable path. The idea is simple: predictability minimizes surprises for the other vessel.

• Give-way vessel: The vessel that must yield and adjust course or speed to avoid a collision. This is the one you’ll hear more about when two boats converge.

These roles aren’t arbitrary. They’re designed to reduce ambiguity in crowded waters. The moment the give-way vessel delivers a clear, early, and substantial change—or fails to do so—the dynamic shifts. And that’s where the stand-on vessel’s hands-on moment arrives.

What does “early and substantial action” actually mean?

• Early action: Acting with enough lead time so the other vessel can see, interpret, and respond. It’s about timing. If you wait until the last moment, you’ve missed the window to communicate intent safely and you’ve put both vessels at risk.

• Substantial action: A maneuver that meaningfully alters collision risk. It isn’t a tiny nudge or a vague change in speed; it’s a clear and decisive adjustment—such as altering course by a noticeable angle or reducing speed to increase separation.

In practice, “early and substantial” isn’t a magic checklist you tick off. It’s a sense of when the risk of collision becomes unacceptable, and when the other vessel’s actions aren’t reducing that risk in a timely way. When that sense is triggered, the stand-on vessel may take action to prevent a crash.

A simple way to picture it

Imagine you’re driving on a winding road with two cars approaching from opposite directions, both aiming for the same narrow lane. If the other driver hesitates or sticks with their speed without clearly easing the risk, most people would adjust—step on the brakes, steer a bit to the shoulder, or slow down to let the other vehicle complete its maneuver safely. In the maritime world, the same logic applies, but with ships and the sea as the stage.

Where weather and visibility fit in

Weather and visibility do complicate things, but they don’t change the fundamental rule. Fog, rain, or darkness can erode the ability to perceive the other vessel’s intentions or movements. In those cases, the importance of early signals, clear radar or AIS information, and a conservative approach grows. The stand-on vessel still relies on predictability, but it also keeps a larger margin for error when lines of sight are compromised. The take-away? Visibility doesn’t create a new exception; it reinforces the need for prudent, timely decisions and clear communication.

Common scenarios and how the rule plays out

• Crossing situation: You’re the stand-on vessel when you have the other boat on your starboard side and you’re on a path to cross. If the give-way vessel on your opposite side doesn’t slow down or alter course early and decisively, you may need to adjust to maintain safety. The goal is to prevent a situation where either vessel has to make a frantic, last-second move.

• Head-on situation: This one gets the most attention in training because the tension is high. If both vessels see the risk and one promises to yield, the other may continue straight only until it becomes clear the other vessel isn’t taking the necessary action. If the give-way vessel misses that opportunity, the stand-on vessel may take action to avoid a collision—while still respecting the general duty to hold course when the other vessel is clearly acting in a predictable, timely way.

• Overtaking: The overtaking vessel has a different set of rules, but the same principle applies: if the give-way vessel isn’t taking early and substantial action to avert danger, the stand-on vessel remains accountable for ensuring safe progress and can adjust if needed.

Practical actions at the helm

• Vigilant lookout: The best defense is noticing a potentially dangerous convergence early. This means using all available tools—radar, AIS, lights, sound signals—to gather a complete picture.

• Clear communication: Sound signals, if required by the situation, can help convey intent. In modern practice, radio and AIS alerts also play a role in reducing uncertainty.

• Decisive maneuvering when needed: If the give-way vessel isn’t acting in time, you might alter your own course or slow down in a controlled, predictable way to increase separation. The key is to act in a way that other mariners can clearly anticipate.

• Keep a buffer: Especially in busy channels or reduced visibility, a wider margin of safety gives you room to respond if the other vessel finally acts.

Common misconceptions worth clearing

• The stand-on vessel must never move: Not true. The stand-on vessel should maintain its predictable path unless there’s a clear, imminent risk and the give-way vessel isn’t acting early and substantially to avoid it.

• If you’re following the rules, you’re never allowed to make a change: The rules anticipate dynamic situations. If the risk of collision increases due to the other vessel’s inaction, it’s correct and prudent to take action to prevent danger.

• Weather always excuses delays: Weather can complicate decisions, but it doesn’t erase the obligation to act promptly when safety demands it.

A few practical tips for situational awareness

• Practice risk assessment: Constantly weigh the possibility of misinterpretation. If a vessel’s bearing and speed suggest a collision risk, be prepared to respond, even if you technically have the “right of way.”

• Anticipate the other guy: Not everyone reads signals the same way. Give-way vessels can be slow to respond, and stand-on vessels can’t assume the other boat will act as expected.

• Keep your crew informed: In a crewed vessel, quick, clear communication onboard is as important as the on-water actions. Short, precise commands help crews coordinate a safe response.

• Rehearse in your mind the three Cs: communicate, confirm, and compensate. Communicate your intentions, confirm others’ actions, and compensate with adjustments that keep you on a safe track.

A quick recap you can keep on hand

• The stand-on vessel has the right of way and should maintain course and speed.

• The stand-on vessel may act to avoid a collision if the give-way vessel does not take early and substantial action to avoid danger.

• Early and substantial action means a timely, definite maneuver that meaningfully reduces risk.

• Weather and visibility affect how actions are perceived, but they don’t negate the core rule—predictability and timely response remain essential.

• Real-world scenarios—crossing, head-on, and overtaking—show how the same principle plays out in different contexts.

• Always prioritize a clear lookout, effective communication, and a measured, decisive response when risk arises.

Bringing it home: safety as a shared responsibility

There’s a rhythm to maritime safety that isn’t about winning a contest or proving a point. It’s about making sure every voyage is safer than the last. The stand-on vessel isn’t finished with its job the moment it’s granted the right of way. Instead, it stays ready to respond if the other vessel’s actions don’t rise to the level of early and substantial effort to prevent a collision. In practice, that patience—paired with readiness to act if needed—keeps everybody safer and the water a little calmer.

If you’re new to COLREGs or you’re revisiting the rules after a break, here’s a simple mental anchor: stay predictable, watch closely for how others respond, and be ready to adjust if timing and action don’t align in a way that reduces risk. The sea will always throw curveballs—the trick is to meet them with clear focus, steady hands, and a plan that puts safety first.

Want a quick mental check before you head back to the helm? Ask yourself:

• Is the other vessel showing early and substantial action to avoid you?

• If not, can you make a deliberate, safe adjustment that others can anticipate?

• Are you maintaining a clear look-out and using signaling or communication to confirm intent?

If you can answer yes to those questions, you’re applying the rule as it’s meant to be applied: with care, clarity, and a steady eye on safety. The water rewards the mariner who blends technical discipline with practical judgment—and that combination is what keeps journeys from becoming stories you hear about later on.