Rule 17 — Action by the Stand-On Vessel

TL;DR — The stand-on vessel must initially keep her course and speed, but may maneuver independently once it is apparent the give-way vessel is not acting, and must maneuver when collision cannot be avoided by the give-way vessel alone. In a crossing situation, a power-driven stand-on vessel shall not alter course to port for a vessel on her own port side. 33 CFR §83.17

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What the Rule Says

Rule 17 is codified at 33 CFR §83.17 and applies only when vessels are in sight of one another — that is, when one can be observed visually from the other. 33 CFR §83.03 33 CFR §83.11

The rule operates in three sequential stages:

Stage 1 — Mandatory: Keep Course and Speed

"Where one of two vessels is to keep out of the way, the other shall keep her course and speed." 33 CFR §83.17

Once the Rules assign one vessel the give-way role and the other the stand-on role, the stand-on vessel's primary obligation is to maintain her course and speed. This predictability is the foundation of the collision-avoidance system: the give-way vessel needs a stable target to maneuver around. Any premature deviation by the stand-on vessel can confuse the give-way vessel and increase collision risk.

Stage 2 — Permissive: Independent Action When Give-Way Vessel Fails to Act

"The latter vessel may, however, 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." 33 CFR §83.17

This is the permissive stage. The stand-on vessel is not yet required to maneuver, but she is authorized to do so once it becomes apparent — not merely suspected — that the give-way vessel is failing to comply. The word "apparent" sets a threshold: the stand-on mariner must have a reasonable, observable basis for concluding the give-way vessel is not acting. Waiting too long to invoke this authority can compress the time available for effective action.

Any action taken at this stage must comply with the general collision-avoidance requirements of Rule 8: it shall be positive, made in ample time, and large enough to be readily apparent to another vessel observing visually or by radar. A succession of small alterations should be avoided. 33 CFR §83.08

Stage 3 — Mandatory: Last-Resort Action

"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." 33 CFR §83.17

This is the mandatory stage. When the situation has deteriorated to the point that even a perfectly executed give-way maneuver cannot prevent collision, the stand-on vessel must act. The rule does not prescribe a specific maneuver — it requires whatever action "will best aid to avoid collision." This may include stopping, reversing, or altering course. Rule 8 reinforces that if necessary, a vessel shall slacken speed or take all way off by stopping or reversing her means of propulsion. 33 CFR §83.08

The Port-Side Restriction in Crossing Situations

"A power-driven vessel which takes action in a crossing situation in accordance with paragraph (a)(ii) of this Rule 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." 33 CFR §83.17

This sub-paragraph applies specifically when: 1. The encounter is a crossing situation between two power-driven vessels. 2. The stand-on vessel is invoking the Stage 2 permissive authority. 3. The give-way vessel is on the stand-on vessel's port side.

In that scenario, the stand-on vessel shall not alter course to port. Turning to port would swing the stand-on vessel's bow toward the give-way vessel, reducing separation and increasing collision risk. The preferred action is an alteration to starboard or a reduction in speed.

Give-Way Obligation Survives

"This Rule does not relieve the give-way vessel of her obligation to keep out of the way." 33 CFR §83.17

Even after the stand-on vessel takes independent action, the give-way vessel remains bound by Rule 16 to take early and substantial action to keep well clear. 33 CFR §83.16 The stand-on vessel's maneuver does not transfer the give-way obligation or extinguish it.

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Why It Matters on the Exam

Exam questions on Rule 17 test whether candidates understand the sequential, conditional structure of the rule. The USCG exam frequently presents scenarios in which you must identify:

1. Which stage applies — mandatory keep-course-and-speed, permissive independent action, or mandatory last-resort action. 2. What maneuver is prohibited — specifically, the port-side restriction in crossing situations. 3. Whether Rule 17 applies at all — it only applies to vessels in sight of one another. 33 CFR §83.11 In restricted visibility, vessels not in sight of one another are governed by Rule 19, not Rules 11–18. 33 CFR §83.19 4. Whether the give-way obligation survives — it does, regardless of what the stand-on vessel does. 33 CFR §83.17

A common exam stem reads: "You are the stand-on vessel in a crossing situation. The give-way vessel is on your port bow and is not taking action. You decide to maneuver. Which alteration is prohibited?" The answer is an alteration of course to port. 33 CFR §83.17

Another frequent stem: "At what point is the stand-on vessel required — not merely permitted — to take action?" The answer is when the situation is so close that collision cannot be avoided by the give-way vessel's action alone. 33 CFR §83.17

Rule 17 also intersects with Rule 8's requirement that any avoiding action be large enough to be readily apparent to another vessel. 33 CFR §83.08 Candidates must understand that even when the stand-on vessel is authorized to maneuver, that maneuver must meet Rule 8 standards — not a series of small, tentative course changes.

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Common Pitfalls

Pitfall 1 — Confusing "may" with "shall" in Stage 2. Stage 2 is permissive: the stand-on vessel may act. Stage 3 is mandatory: she shall act. Exam distractors often swap these words. Read the question carefully to determine which stage the scenario describes.

Pitfall 2 — Applying Rule 17 in restricted visibility. Rule 17 is part of Rules 11–18, which apply only to vessels in sight of one another. 33 CFR §83.11 "In sight" means visual observation — radar contact alone does not satisfy this definition. 33 CFR §83.03 When vessels are not in sight of one another in or near restricted visibility, Rule 19 governs. 33 CFR §83.19 Applying Rule 17 to a fog scenario is a classic error.

Pitfall 3 — Forgetting the port-side restriction applies only to power-driven vessels in a crossing situation. The prohibition on altering course to port is limited to: (a) power-driven vessels, (b) in a crossing situation, (c) acting under Stage 2 authority. It does not apply to sailing vessels, to head-on situations, or to Stage 3 last-resort action where the vessel must take whatever action best aids collision avoidance.

Pitfall 4 — Believing the stand-on vessel's action relieves the give-way vessel. Rule 17(d) is explicit: the give-way vessel's obligation under Rule 16 survives regardless of what the stand-on vessel does. 33 CFR §83.17 33 CFR §83.16 Both vessels may be found at fault in a collision if each failed its respective obligation.

Pitfall 5 — Taking small, incremental course changes. Rule 8 requires that any alteration be large enough to be readily apparent to another vessel observing visually or by radar, and cautions against a succession of small alterations. 33 CFR §83.08 A stand-on vessel that nibbles at the helm in small increments is not complying with the Rules even if she is technically authorized to maneuver.

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Quick Check

Q1 — You are the stand-on vessel in a crossing situation. The give-way vessel is on your port bow and has not altered course or speed. You decide to take independent action under Rule 17(a)(ii). Which course alteration is prohibited?

An alteration of course to port is prohibited. A power-driven stand-on vessel in a crossing situation acting under Rule 17(a)(ii) shall not alter course to port for a vessel on her own port side, if the circumstances of the case admit. 33 CFR §83.17

Q2 — At what point does the stand-on vessel's obligation shift from "may maneuver" to "shall maneuver"?

The obligation becomes mandatory when the stand-on vessel finds herself so close that collision cannot be avoided by the action of the give-way vessel alone. At that point she shall take such action as will best aid to avoid collision. 33 CFR §83.17

Q3 — You are in dense fog and detect another vessel by radar only. Does Rule 17 govern your conduct?

No. Rule 17 is part of Rules 11–18, which apply only to vessels in sight of one another — meaning visual observation. 33 CFR §83.11 33 CFR §83.03 A radar contact alone does not place vessels in sight of one another. Conduct in restricted visibility when vessels are not in sight of one another is governed by Rule 19. 33 CFR §83.19

Q4 — The stand-on vessel takes independent action under Rule 17(a)(ii). Is the give-way vessel now relieved of her obligation to keep out of the way?

No. Rule 17(d) expressly states that the rule does not relieve the give-way vessel of her obligation to keep out of the way. 33 CFR §83.17 The give-way vessel remains bound by Rule 16 to take early and substantial action to keep well clear. 33 CFR §83.16

Q5 — What standard must any avoiding action taken by the stand-on vessel meet under Rule 8?

Any action shall be positive, made in ample time, and with due regard to good seamanship. Any alteration of course and/or speed shall be large enough to be readily apparent to another vessel observing visually or by radar. A succession of small alterations of course and/or speed should be avoided. 33 CFR §83.08

Q6 — Does the port-side course restriction in Rule 17(c) apply to a sailing vessel stand-on vessel in a crossing situation?

No. Rule 17(c) applies specifically to a power-driven vessel taking action in a crossing situation under Rule 17(a)(ii). The restriction does not extend to sailing vessels. 33 CFR §83.17