Rule 17 — Holding On, and the Two Points Where You Stop Holding

What the rule requires

Rule 17 has three settings, and almost every exam question on it is asking which setting you are in and whether the verb is shall or may.

Setting one — hold. Where one of two vessels is to keep out of the way, the other shall keep her course and speed 33 CFR §83.17. The trigger is nothing more than the existence of a give-way vessel in the encounter. Nothing about size, nothing about tonnage, nothing about who saw whom first. If the Rules put the burden on her, the duty on you is course and speed — and that duty is mandatory, not a courtesy.

Setting two — you may act alone. The stand-on vessel may take action to avoid collision by her maneuver alone as soon as it becomes apparent to her that the vessel required to keep out of the way is not taking appropriate action in compliance with these Rules COLREGs Rule 17(a). Learn that clause close to verbatim, because it contains the two things an exam question turns on. First, the trigger is apparency — what has become apparent to you about her conduct, not a fixed range and not a fixed number of minutes. Second, the verb is may. Permission, not obligation. An option that tells you that you must maneuver the moment the other vessel fails to act is describing a rule that does not exist.

Setting three — you must act. When, from any cause, the vessel required to keep her course and speed finds herself so close that collision cannot be avoided by the action of the give-way vessel alone, she shall take such action as will best aid to avoid collision COLREGs Rule 17(b). Two phrases carry the weight. So close that collision cannot be avoided by the action of the give-way vessel alone is the trigger, and it is a judgement about what her maneuver can still achieve, not about her intentions. From any cause means the paragraph applies whether or not she is the one who put you there; your own earlier conduct does not disable it. And the standard is what will best aid to avoid collision — the best available action, not a textbook one. Instructors and case law commonly call this stage in extremis; the phrase appears nowhere in the Rule, and it will not appear in an exam answer key.

The one restriction on setting two. A power-driven vessel taking action in a crossing situation under paragraph (a)(ii), to avoid collision with another power-driven vessel, shall — if the circumstances of the case admit — not alter course to port for a vessel on her own port side COLREGs Rule 17(c). Read the qualifiers, because they are what the distractors are built from: power-driven against power-driven, a crossing situation, and action taken under (a)(ii). The prohibition is on one thing only, an alteration of course to port toward a vessel on your own port side. A reduction of speed is not touched by it, and neither is a turn to starboard.

And the give-way vessel is still the give-way vessel. Rule 17 does not relieve her of her obligation to keep out of the way . Your holding on does not transfer her duty to you, and your maneuvering under (a)(ii) or (b) does not discharge it for her. Both vessels can be, and routinely are, found in breach of the same encounter.

You are the stand-on vessel in a crossing situation. The other vessel has made no alteration at three miles and the bearing is steady. Are you required to maneuver?

No. Once it has become apparent she is not taking appropriate action, Rule 17(a)(ii) permits you to take action by your own maneuver alone — the verb is "may". The requirement to act arrives only under 17(b), when you are so close that collision cannot be avoided by her action alone. Meanwhile 17(a)(i) still has you keeping course and speed. Both International and Inland.

Telling it apart

Candidates lose points on Rule 17 by mixing up its own two action paragraphs far more often than by mixing Rule 17 with any other rule. The single criterion that separates them: can the give-way vessel's action, by itself, still avoid collision?

• Rule 17(a)(ii) — she can still fix it, but is not. Yes, her maneuver alone would still do the job; she just is not making it. Permission opens for you to maneuver alone. Your action is constrained by 17(c) where the encounter is power-driven against power-driven in a crossing situation. Most often misfiled: candidates treat the apparency of her failure as an obligation on themselves and choose the answer that says "you must alter course".
• Rule 17(b) — her action alone is no longer enough. No, you are so close that her maneuver cannot avoid collision. Action is now required of you, and the measure is what will best aid to avoid collision. Most often misfiled: candidates believe the stand-on vessel holds course and speed to the point of impact, and choose "maintain course and speed" on a question that has plainly reached this stage.

Note also which paragraph 17(c) is written against. It restricts a vessel "which takes action in a crossing situation in accordance with paragraph (a)(ii)" COLREGs Rule 17(c). By its own words, the port-turn restriction is keyed to the permissive stage. Answer the exam on the words: a stand-on vessel taking action to avoid collision shall not, if circumstances admit, alter course to port for a vessel on her own port side.

On the International-versus-Inland axis this topic is a gift. Inland Rule 17 is word-for-word identical to the International rule COLREGs Rule 17, so there is no divergence to remember and no reason to hedge — every fact above answers "Both International & Inland".

Working a question

Take a concrete encounter. You have the conn of a power-driven vessel making 12 knots in clear visibility. Another power-driven vessel is on your port bow, range 4 miles, and the question establishes that she is the vessel required to keep out of the way. Work it in the order the Rule works.

1. Fix your duty from the geometry the question gives you. She is to keep out of the way; therefore you shall keep your course and speed 33 CFR §83.17. At 4 miles with the burden on her, any answer that has you maneuvering is wrong on the words of 17(a)(i).
2. Watch her bearing, and watch it against the clock. Range 3 miles, bearing unchanged, no alteration of her course, no change in her aspect. That evidence — not the range figure by itself — is what makes it apparent she is not taking appropriate action in compliance with the Rules.
3. Once it is apparent, know what has changed and what has not. Rule 17(a)(ii) has opened permission for you to avoid collision by your maneuver alone COLREGs Rule 17(a). It has not imposed a duty. If the stem asks what you are required to do at this instant, the answer is still course and speed. If the stem asks what you may do, the answer is that you may maneuver.
4. If you elect to act, pick an action 17(c) allows. Power-driven against power-driven, crossing, action under (a)(ii), and she is on your own port side: you do not alter course to port toward her COLREGs Rule 17(c). A substantial alteration to starboard is available. So is taking off speed, which the restriction never mentions.
5. If it deteriorates instead, recognise the switch. Range 0.4 mile, bearing still steady, and her maneuver alone can no longer avoid collision. You are now under 17(b) and action is mandatory — such action as will best aid to avoid collision COLREGs Rule 17(b). The paragraph runs from any cause, so it applies even if your own delay contributed to the closeness.
6. Do not let your action rewrite hers. Her obligation to keep out of the way survives everything you do . An option offering that she is relieved once you begin to maneuver is contradicted by paragraph (d) directly.

The pattern generalises: read the stem for which stage it has put you in, then match the verb. Stage one takes shall hold, stage two takes may act, stage three takes shall act.

Where candidates lose the point

Choosing "maintain course and speed" on a close-quarters stem. This is the single most common error on Rule 17, and it attracts because "the stand-on vessel holds course and speed" is the first thing anyone learns about the Rule. It is only 17(a)(i). Once you are so close that collision cannot be avoided by the give-way vessel alone, holding on is a breach of 17(b), which says you shall take such action as will best aid to avoid collision.

Choosing "you must alter course now" as soon as the give-way vessel is seen doing nothing. The over-corrected version of the error above. Rule 17(a)(ii) says the stand-on vessel may take action; the obligation belongs to 17(b) and to no earlier point. Watch for stems that ask what you are "required to" do — that wording is testing exactly this line.

Choosing an alteration to port to open the range on a vessel to port. It looks like a turn away from the problem. In a crossing situation between power-driven vessels, taking action under (a)(ii), 17(c) tells you not to alter course to port for a vessel on your own port side.

Reading 17(c) as a blanket prohibition on ever turning to port. The paragraph is fenced by its own terms — power-driven against power-driven, a crossing situation, action under (a)(ii), and "if the circumstances of the case admit" COLREGs Rule 17(c). An option stating that a stand-on vessel may never alter to port under any circumstances overstates it.

Believing 17(b) applies only when the other vessel is at fault. The paragraph opens "when, from any cause". Nothing in it requires that the fault be hers.

Treating the give-way vessel as released once you maneuver. Paragraph (d) is one sentence and exists for this distractor alone.

Answering "International Only" or "Inland Only" on a Rule 17 question. The two regimes are identical here COLREGs Rule 17. If the alternatives on the answer sheet include a regime label, take "Both".

Check yourself

You are the stand-on vessel in a crossing situation with another power-driven vessel on your port side. It has become apparent she is not taking appropriate action. You decide to maneuver. Which action does the Rule prohibit, if circumstances admit?

Altering course to port. Rule 17(c) bars a power-driven vessel taking action under (a)(ii) in a crossing situation from altering course to port for a vessel on her own port side, if the circumstances of the case admit. A substantial alteration to starboard, or a reduction of speed, is not prohibited. Both International and Inland.

Under Rule 17, when does action by the stand-on vessel change from permitted to required?

When, from any cause, she finds herself so close that collision cannot be avoided by the action of the give-way vessel alone. At that point 17(b) requires such action as will best aid to avoid collision. Before that, 17(a)(ii) only permits her to act once it is apparent the give-way vessel is not taking appropriate action.

A vessel required to keep out of the way holds her course while you, the stand-on vessel, maneuver early under Rule 17(a)(ii). Is she still obliged to keep out of the way?

Yes. Rule 17(d) states the Rule does not relieve the give-way vessel of her obligation to keep out of the way. Your action neither discharges her duty nor transfers it.

What exactly must have become apparent to you before Rule 17(a)(ii) permits you to maneuver?

That the vessel required to keep out of the way is not taking appropriate action in compliance with the Rules. The trigger is apparency of her non-compliance, not a specific range, a specific time to CPA, or a signal exchange.

You are the stand-on vessel and your own late assessment contributed to how close the two vessels now are. Does Rule 17(b) still apply to you?

Yes. Rule 17(b) applies when "from any cause" you find yourself so close that collision cannot be avoided by the give-way vessel's action alone. The cause is immaterial to the duty; you shall take such action as will best aid to avoid collision.

An exam question on the stand-on vessel's duty to keep her course and speed is labelled how — International Only, Inland Only, or Both?

Both. Inland Rule 17 is word-for-word identical to the International rule, so every part of Rule 17 answers "Both International & Inland".

A stand-on vessel is permitted to take action to avoid collision "by her maneuver alone". What does the Rule require of her before that permission opens?

That she keep her course and speed, under 17(a)(i), for so long as the other vessel is the one required to keep out of the way and it has not become apparent that she is failing to take appropriate action.