Rule 15: Power-driven vessels in crossing situations have clear give-way and stand-on responsibilities

Rule 15: The crossing rule you’ll hear a lot on the water

Let’s set the scene. You’re steering along a busy waterway, maybe near a harbor entrance, perhaps a river mouth where traffic weaves in and out. A second vessel appears on a path that intersects yours. It’s a crossing situation, the kind that trips up even seasoned skippers if they forget who should give way. Rule 15 of the COLREGs is designed for exactly this moment—when power-driven vessels cross paths and there’s a real chance of collision.

What Rule 15 actually covers

Here’s the core idea, kept simple: Rule 15 addresses crossing situations between power-driven vessels. It tells us who must yield and who keeps their course and speed. In practical terms, the vessel that has the other vessel on its starboard side is the give-way vessel. The other vessel—whose own path has the other vessel on its port side—is the stand-on vessel. The stand-on vessel should maintain its course and speed unless it becomes clear that the give-way vessel isn’t taking action, in which case both boats may need to adjust.

A quick mental picture helps. If Boat A sees Boat B on its starboard side (to the right), Boat A is the give-way vessel. Boat B, which has Boat A on its port side (to the left), is the stand-on vessel. The job of Boat A is to take early and substantial action to avoid a collision; Boat B should keep its course and speed unless it’s obvious that Boat A won’t budge, in which case Boat B would need to take evasive action too.

Common myths, cleared up

There are a few easy-to-mumble misstatements floating around the marina, so let’s clear them up with honesty.

• It’s not “every vessel” Rule 15. It’s specifically about crossing situations and, in particular, interactions between power-driven vessels. Sailing vessels follow Rule 18 and related rules that take their own unique twists into account.

• It isn’t limited to sailing vessels. And it isn’t limited to a certain zone or a certain kind of craft. The essential factor is the crossing geometry and the power-driven status of the vessels involved.

• It isn’t about moored boats. When vessels are moored together, you’re in a completely different realm of rules—no crossing scenario to negotiate at speed.

• It doesn’t say “the give-way must crash out of the way.” It says give-way vessels should take early and substantial action to avoid a collision, which can mean slowing down, changing course, or a combination of both. The emphasis is on clear, timely action, not panic.

A simple example most people can relate to

Picture two motorboats approaching an intersection of channels near a busy harbor. Boat A is coming from the starboard side of Boat B. Under Rule 15, Boat A must take action to avoid. It could ease off speed, alter course a bit to port, or a combination of maneuvering moves that ensure the other vessel has a safe path. Boat B should keep its course unless the situation demands it, for example, if it becomes clear that Boat A is not responding quickly enough.

This is why keeping a steady lookout matters. It’s not just about the rules on paper; it’s about reading the situation, confirming your relative bearings, and communicating if needed. A quick radio call on VHF Channel 16 to clarify intentions can be a practical bridge between the law and actual safe maneuvering. Radar, AIS, and even a simple magnified glance through the binoculars all help you judge the range and closing speed. The goal isn’t to “win” a theoretical tug-of-war; it’s to secure a safe passage for everyone involved.

Why Rule 15 sits where it does in the code

Colregs aren’t a random collection of dos and don’ts. They mirror the realities of the sea—the fact that some vessels have more maneuverability or speed, and that angles and distances change how quickly a collision can occur. Rule 15 reflects two realities:

• The stand-on vessel is not passive. It keeps its course and speed unless the risk increases to a point where continuing on the current track would be unsafe.

• The give-way vessel must act decisively. The moment a decision point is reached, the give-way vessel should begin the necessary action early. Waiting too long is exactly what Rule 15 tries to prevent.

If you’ve ever watched two boats in a crossing and seen one slip over just as the other holds steady, you’ve seen the Rule 15 idea in motion. The practical takeaway is to develop a habit: scan for potential crossers, identify if you’re on their starboard or port, and plan a safe response before the situation deteriorates.

A few practical tips that stick

• Always know your relative bearing. If another vessel’s path would cross yours and your boat sits with them on your starboard or port side, you’re entering the Rule 15 zone.

• Stay predictable. Smooth, steady speed and a clear, purposeful course help the other vessel judge what you’ll do next. Sudden, erratic changes raise the risk of misinterpretation.

• Don’t rely on signaling alone. A light or horn signal can help, but your primary tool is your maneuverability and timing. Signals are supplementary—use them to confirm intent, not replace action.

• Communicate when needed. If there’s any doubt, a quick radio call or even a loud but short horn blast can reduce uncertainty. A calm message like “I’ve got you on my starboard; I’ll adjust course to port” can avert tension and near-misses.

• Integrate with the bigger picture. Rule 15 doesn’t live in isolation. It sits next to Rule 14 (read and keep clear of the danger), Rule 16 (action by give-way vessels in head-on and near-head-on situations), and Rule 17 (the stand-on vessel shall not hamper the give-way vessel’s maneuver). A good navigator knits these together in real time.

If you’re wondering when Rule 15 matters most, think about busy waterways, inland rivers, or ports where traffic lanes feel like a grid. Even a small powerboat crossing a busy channel with a larger vessel moving quickly can trigger the rule in a heartbeat.

Turning theory into a confident mindset

The Rule 15 mindset is part law, part real-world common sense. It’s the habit of looking ahead, not just at the vessel directly in front of you but at the flow of boats around you—the automatic glance at a potential starboard crossing and the instinct to plan action early.

And yes, there are edge cases that challenge the neat rulebook. For instance, if the stand-on vessel discovers that the give-way vessel is not taking action, or if the stand-on vessel itself becomes the risk to others, then deviations from the standard expectation are warranted. It’s not a failure of the rules to adapt; it’s a sign you’re using them with judgment.

A few extra notes you might find handy

• Rule 15 is not a solo act. It interacts with other crossing scenarios, including those where one or both vessels are sailing (which falls under different rules) or where there’s a potential collision with a fishing vessel or a vessel not under command.

• The human factor matters. Fatigue, distraction, and weather all influence reaction time. Good seamanship isn’t just about knowing the rule; it’s about applying it when the wind shifts, the current lurches, or visibility drops.

• Tools can help, but they don’t replace good judgment. Equipment like a chart plotter, radar, AIS, or VHF radio adds clarity, but the core skill remains the same: identify the crossing, figure out who has the other on their starboard, and act promptly.

Putting the rule into everyday practice

If you’re out on the water with friends, or just training mentally between sails and motor runs, take a moment to visualize Rule 15 in a couple of scenarios. Picture a power-driven boat meeting another from the starboard side as they converge on a channel. The give-way vessel acts early; the stand-on vessel keeps steady. Now imagine a second scenario, where the other boat slips a touch closer on the starboard front, and you realize you need to compensate. You’re not just following a rule—you’re steering toward safety with a calm, deliberate plan.

Key takeaways you can carry with you

• Rule 15 governs crossing situations between power-driven vessels.

• The vessel with the other on its starboard side is the give-way vessel.

• The stand-on vessel maintains course and speed unless risk demands action.

• It’s about early, substantial action to prevent collision, not about winning a game of who yields first.

• It’s best used alongside tools like radar, AIS, and good lookouts, with clear communication when needed.

Closing thought — a practical mindset for the water

Navigating Rule 15 isn’t about memorizing a single line; it’s about building a reliable reflex. On the water, safety hinges on your ability to see a crossing well before it becomes urgent and to act in a way that leaves room for others to respond. When the starboard side is involved, you’re entering a shared space where mariner judgment, steady hands, and calm decisions keep the voyage smooth and safe.

If you’ve found this breakdown helpful, you’ll likely notice Rule 15 popping up in real-life sightings and in more nuanced scenarios as you gain experience. The sea rewards thoughtful, practiced decision-making—the kind that blends technical rules with practical, human judgment. And that blend is what makes sailing and boating both a challenge and a joy.