Overtaking: the duty that does not shift

What the rule requires

The overtaking vessel keeps out of the way of the vessel being overtaken, and that duty is written to defeat competing claims: 33 CFR §83.13 states it "notwithstanding anything contained in Rules 4 through 18 (§§ 83.04 through 83.18)." Nothing inside that span of rules can be raised to argue that the overtaking vessel is the stand-on vessel. The International text carries the identical duty, with the override expressed as the Rules of Part B, Sections I and II COLREGs Rule 13.

Read the subject of that sentence closely. It is "any vessel overtaking any other" — no class of vessel is written out of it, and it is not confined to power-driven vessels. A sailing vessel coming up on a power-driven vessel from astern is the vessel that keeps clear.

When you are deemed to be overtaking

A vessel is deemed to be overtaking when coming up with another vessel from a direction more than 22.5 degrees abaft her beam. The pronoun matters on the exam: the arc is measured from the beam of the vessel being overtaken, not from your own beam or your own heading.

The rule then supplies its own field test, which is why the number is worth learning together with the light picture: from that position, at night you would be able to see only the sternlight of that vessel and neither of her sidelights. One glance settles it. Sternlight alone, no red and no green, and you are the overtaking vessel.

The 22.5 degree figure is a boundary you must simply carry in; the rule does not derive it, it declares it, and it pairs it with the light cut so that a mariner on watch can apply it without a bearing.

At night you are closing on a tug and see her white sternlight and, intermittently, her green sidelight. Are you deemed to be overtaking under Rule 13?

No. The deeming test in Rule 13(b) is met only when you would see her sternlight and neither of her sidelights. A sidelight in view puts you forward of the 22.5 degree line. That does not end the matter — if you are in any doubt about your position relative to that line, Rule 13(c) requires you to assume you are overtaking and act accordingly .

Doubt runs one way only

When a vessel is in any doubt as to whether she is overtaking another, she shall assume that this is the case and act accordingly COLREGs Rule 13(c). The threshold is "any doubt," not reasonable doubt, and the assumption imposed on you is the burdensome one. There is no reading of Rule 13 under which uncertainty lets you hold course and speed.

The duty persists until finally past and clear

Any subsequent alteration of the bearing between the two vessels does not make the overtaking vessel a crossing vessel within the meaning of the Rules, nor relieve her of the duty of keeping clear until she is finally past and clear COLREGs Rule 13(d).

Instructors teach this as once an overtaking vessel, always an overtaking vessel, and that is the phrase in general circulation. It carries the right idea and one wrong implication, so take the correction with it: the duty is not permanent, it ends at the moment you are finally past and clear. What is permanent is that the bearing cannot end it early.

International and Inland

Paragraphs (b), (c) and (d) are word for word the same in both regimes, and paragraph (a) imposes the same duty in both. What differs is the scope language of paragraph (a): the Inland text overrides Rules 4 through 18 (§§ 83.04 through 83.18) at , while the International text overrides the Rules of Part B, Sections I and II. On top of that difference the Rule 13 material carries an express caution — Inland Rule 13 differs from the International rule, and the two are to be compared before answering a question that turns on which set applies .

So read the label, and read what the question actually turns on. If the answer rests on the deeming test, the doubt provision or the endpoint, the two texts will take you to the same place. If it rests on the reach of paragraph (a) — which rules are displaced, and by what name they are identified — set the two texts side by side and work from the one the label names. Treating the label as noise is how a candidate loses that question.

Telling it apart: overtaking against crossing

The argument that puts vessels alongside each other is always the same one. You believe you are overtaking her; she believes she is being crossed and holds on. Rule 13 settles it, and it settles it with two criteria.

• The initial approach bearing is the criterion that decides which rule you are in. More than 22.5 degrees abaft her beam, confirmed at night by her sternlight with neither sidelight showing, and you are deemed overtaking 33 CFR §83.13.
• Doubt about that bearing does not leave the question open. Rule 13(c) forces the answer to overtaking and requires you to act on it.
• A change of bearing after the fact decides nothing. Rule 13(d) is explicit that a later alteration of the bearing does not make the overtaking vessel a crossing vessel.

The case most often misfiled is the slow closure from broad on the quarter that gradually draws forward as you come up on her. By the time the two vessels are close, the bearing looks like a crossing, and the watch officer who started abaft her beam talks himself into stand-on status. Rule 13(d) exists to shut that reasoning down.

You began the approach from well abaft her beam. Twenty minutes later she bears three points on your starboard bow and you can see her port sidelight. Which rule governs?

Rule 13 still governs, and you are still the vessel that keeps out of the way. The alteration of bearing has not made you a crossing vessel and has not relieved you of the duty, which runs until you are finally past and clear COLREGs Rule 13(d).

Working a question

A question puts you on the vessel and asks what you must do. Work it in this order every time.

You are on a 78 GT passenger vessel making 14 knots on a clear night, steady on 090. You have a white light ahead, bearing steady at 095, closing slowly. As you draw up, you make out a second white light and no coloured light at all.

1. Read the label. Note whether the question is set under International, Inland, or both, and keep the corresponding text in front of you for any step that turns on the scope of paragraph (a).
2. Establish the light picture. No red, no green, sternlight only. That is the direction described in Rule 13(b) — more than 22.5 degrees abaft her beam.
3. Apply the deeming provision. You are coming up with her from that direction, so you are deemed to be overtaking. Rule 13 is now the operative rule.
4. Check what Rule 13 displaces. On inland waters the duty applies notwithstanding anything in Rules 4 through 18, so nothing in that span makes you the stand-on vessel here, whatever class of vessel she turns out to be; under the International Rules the displaced body is Part B, Sections I and II.
5. Fix the duty. You keep out of the way of the vessel being overtaken 33 CFR §83.13.
6. Resolve any residual doubt against yourself. If the light picture were ambiguous — a stern quarter aspect you cannot resolve, a sidelight glimpsed and lost — Rule 13(c) requires you to assume you are overtaking rather than wait for certainty.
7. Hold the duty through the pass. As you come up on her beam her bearing will draw aft and you may open her sidelight. Neither event changes your status. You are bound to keep clear until finally past and clear COLREGs Rule 13.
8. End the duty only at that point. Resuming your intended track before you are finally past and clear puts you in breach while she is still entitled to be kept clear of.

The decision that carries the question is step 3. Everything after it follows from the deeming provision, and the distractors on a real exam are written to pull you out of it — by offering a class of vessel that sounds privileged, or by moving the bearing.

Where candidates lose the point

Answering "hold course and speed" because the bearing opened forward. The option is attractive because the geometry at that instant genuinely resembles a crossing. Rule 13(d) forecloses it: a subsequent alteration of bearing does not make the overtaking vessel a crossing vessel or relieve her of the duty.

Measuring the 22.5 degrees from the wrong vessel. Candidates take it off their own beam or their own bow. The rule measures the direction of approach relative to the beam of the vessel being overtaken, and the light test confirms whose beam is meant — you are the one who sees her sternlight.

Treating a visible sidelight as irrelevant. If either of her sidelights is in view, the condition in Rule 13(b) is not satisfied. Candidates who remember only "coming up from astern" answer overtaking to any approach from the after half of the horizon.

Reading "any doubt" as room to negotiate or to wait. Doubt is resolved for you, and it is resolved against you: assume you are overtaking and act accordingly.

Assuming a privileged class of vessel escapes Rule 13. The duty falls on "any vessel overtaking any other," and it applies notwithstanding the rules paragraph (a) displaces — Rules 4 through 18 inland, Part B, Sections I and II internationally. A vessel that would be stand-on in some other encounter still keeps clear when she is the one coming up from astern.

Ending the duty when you draw ahead. The rule sets the endpoint at finally past and clear, not at the moment your stern passes her bow. If she still has to manoeuvre on your account, you have not kept out of her way.

Discarding the International or Inland label as irrelevant to Rule 13. The two texts differ in paragraph (a), and the guidance attached to the rule is to compare them before answering a question that turns on which set applies.

Check yourself

You are overtaking a fishing vessel at night. She is dead ahead and you intend to pass down her starboard side. As you come abeam, she alters to starboard toward you. Whose duty was it to keep clear during that pass, and when did yours end?

Yours throughout, and it ended only when you were finally past and clear. Rule 13(a) places the duty on the overtaking vessel notwithstanding anything in Rules 4 through 18, and Rule 13(d) keeps it on her until she is finally past and clear 33 CFR §83.13.

You are under sail alone, making 9 knots, and coming up from astern on a power-driven tug making 6. Who keeps out of the way?

You do. Rule 13 applies to "any vessel overtaking any other" and overrides the rules paragraph (a) names, so being a sailing vessel gains you nothing in an overtaking situation.

At what bearing relative to the other vessel are you deemed to be overtaking, and what is the corresponding light picture?

More than 22.5 degrees abaft her beam. From there, at night, you would see only her sternlight and neither of her sidelights COLREGs Rule 13.

Fog has just lifted at first light. Your radar plot shows you closing on a contact from somewhere near her quarter, but you cannot resolve whether you are forward or abaft the 22.5 degree line. What does Rule 13 require?

Assume you are overtaking and act accordingly. Rule 13(c) is triggered by any doubt, and it resolves the doubt against the vessel coming up.

An exam question on overtaking is labelled "(International Only)". Does your answer change if the encounter is on inland waters?

The 22.5 degree test, the doubt provision and the persistence of the duty until finally past and clear are stated in the same terms in both texts, so an answer resting on any of those holds on either side of the demarcation line . Do not treat the label as noise, though. Paragraph (a) names a different body of overridden rules in each, and the guidance attached to Rule 13 is to compare the two before answering a question that turns on which set applies . If that is what the question turns on, answer from the text the label names.

You have passed a barge tow and your stern is now about a cable ahead of the tug's bow, but the tug is having to come left to open the distance. Are you past and clear?

No. Being ahead is not the test. The duty to keep out of her way runs until you are finally past and clear, and a vessel still manoeuvring to avoid you has not been kept clear of.

You are the vessel being overtaken and the vessel astern has been closing steadily for ten minutes without altering. What has Rule 13 given you, and what has it not?

It has given you the right to be kept clear of, since the overtaking vessel bears that duty until finally past and clear. It has not given you anything to do in Rule 13 itself; the rule imposes its obligation on the overtaking vessel and says nothing about action by the vessel overtaken.