Rule 17 — Action by stand-on vessel
The rule that changes as the vessels close. First the stand-on vessel must hold her course and speed; then she may act on her own; then she must act. Plus the one alteration Rule 17(c) tells a power-driven stand-on vessel in a crossing to avoid, and the sentence that keeps the give-way vessel's duty in place throughout. Easy to get half right — here it is stage by stage.
Four steps: hold your course and speed (17(a)(i)); you may act by your own manoeuvre once it is apparent the give-way vessel is not acting (17(a)(ii)); you must act once she can no longer avoid collision alone (17(b)); and throughout, the give-way vessel's duty stays with her (17(d)). Paragraph (c) adds one restriction on a power-driven vessel in a crossing.
Rule 17 applies 'where one of two vessels is to keep out of the way' — so the stand-on vessel is the one that Rule 12, 13, 15 or 18 says another must keep out of the way of: the sailing vessel with the wind on the starboard side when the other has it on the port side (or the leeward vessel when both have it on the same side), the vessel being overtaken, the power-driven vessel with the other on her port side in a crossing, and so on.
Like Rule 16, it is in Part B, Section II, which applies to vessels in sight of one another (Rule 11). In restricted visibility, with the other vessel not in sight, there is no stand-on vessel — Rule 19 applies.
The rules do not use that phrase, and as we read it, it misleads. Standing on is a duty — to keep course and speed — not a privilege, and Rule 17 itself goes on to say when the stand-on vessel may act and when she must.
Exactly that, under 17(a)(i): hold both. Speed counts as much as course — slowing down to 'let her pass' is a change of speed, and at this stage the rule asks you not to make one.
The reason, as we read it, is predictability: the give-way vessel plans her action on the assumption that you will hold on, and a stand-on vessel that changes course or speed can undo that plan. Holding on is not the same as waiting passively. Keep taking bearings and ranges (Rule 7) so you know whether the give-way vessel is acting.
'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 the rules. The word is 'may': this stage is a permission, not a duty. She may act, or she may continue to stand on.
The action must be 'by her manoeuvre alone'. As we read it, that means action which avoids collision by itself, whatever the give-way vessel does or fails to do — not a small move that only works if she acts as well. Any action to avoid collision must also meet Rule 8: positive, made in ample time, and readily apparent.
Rule 34(d): in sight of one another and closing, a vessel that fails to understand the other's intentions or actions, or is in doubt whether the other is doing enough to avoid collision, sounds at least five short and rapid blasts, straight away. She may back it up with at least five short and rapid flashes.
In practice that doubt usually comes before the decision to act under 17(a)(ii), so the signal often comes first. If she is a power-driven vessel underway and then alters course or goes astern, Rule 34(a) applies as well: one short blast for an alteration to starboard, two for an alteration to port, three for astern propulsion.
When, 'from any cause', she is so close that the give-way vessel can no longer avoid collision by her own action. Then she must take whatever action 'will best aid to avoid collision'. The permission of stage two has become a duty.
As we read it, 'from any cause' includes her own decision not to act earlier under (a)(ii): waiting does not excuse her from (b). In practice the action that best aids at this range is often the most effective one her vessel has — a large alteration, full astern, or both — chosen for the geometry in front of her.
No. Rule 17 gives no ranges or times. When stage two is reached depends on what is apparent from the bearings and ranges; when stage three is reached depends on the vessels, their speeds, their handling and the sea room. In our view you need to know your own vessel's turning circle and stopping distance to judge either.
17(c) applies to a power-driven vessel taking action under (a)(ii) in a crossing situation, to avoid another power-driven vessel. She shall, if the circumstances of the case admit, 'not alter course to port for a vessel on her own port side'.
In a crossing under Rule 15, the give-way vessel is the one that has the other on her own starboard side — so, seen from the stand-on vessel, the give-way vessel is on her port side. In practice the give-way vessel's action, even a late one, is likely to be an alteration to starboard to pass astern, since Rule 15 asks her to avoid crossing ahead. A stand-on vessel turning to port turns towards her and can meet that alteration.
17(c) rules out one action; it does not prescribe another. As we read it, that leaves an alteration to starboard, a change of speed, or both — whichever will avoid collision by her own manoeuvre.
Not in terms: its text refers to action taken 'in accordance with subparagraph (a)(ii)', and at the 17(b) stage the test is whatever action 'will best aid to avoid collision'. As we read it, the reason behind 17(c) still holds at that range: the give-way vessel's last-moment action is likely to be to starboard, so a turn to port towards her is rarely the action that best aids and would need justifying. Nor does 17(c) apply in terms to a sailing vessel, or to anything other than a crossing between two power-driven vessels.
That the give-way vessel's duty never transfers. Whether the stand-on vessel holds on, acts under (a)(ii), or is forced to act under (b), the give-way vessel is still obliged to keep out of the way. In practice: as the give-way vessel, never wait for the stand-on vessel to sort it out — Rule 16 asks for early and substantial action.
It may come up as a crossing scenario that develops, with the question of what you do at each stage. Examples of the kind of question to be ready for:
“You're the stand-on vessel in a crossing. The vessel on your port bow is on a steady bearing and isn't altering. Talk me through what you do, and when.”
“What does 'by her manoeuvre alone' mean?”
“Why shouldn't you alter to port?”
“At what point must you act, rather than may?”
“What signal do you make if you're in doubt about the other vessel's action?”
“Can the stand-on vessel slow down to let the other vessel cross ahead?”
The common slips: calling the stand-on vessel the 'right of way' vessel; slowing down at stage one; treating (a)(ii) as a duty or (b) as optional — mixing up 'may' and 'shall'; making a small alteration that only works if the give-way vessel also acts; altering to port for a power-driven vessel on the port side in a crossing; forgetting the doubt signal; and claiming stand-on status in restricted visibility.
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