The rule
What does COLREGs Rule 16 say?
If another rule tells you to keep out of the way of a vessel, Rule 16 says how: so far as possible, act early and substantially, and keep well clear. That is the whole rule.
It sits in Part B, Section II, which by Rule 11 applies to vessels in sight of one another. In restricted visibility, with the other vessel not in sight, there is no give-way vessel: Rule 19 applies instead, and every vessel that detects a developing close-quarters situation or risk of collision must act.
Which rules make a vessel the give-way vessel?
The ones that direct a vessel to 'keep out of the way' of another. Rule 12, between two sailing vessels: the one with the wind on the port side keeps out of the way of the one with it on the starboard side; with the wind on the same side, the windward vessel keeps out of the way of the leeward one. Rule 13: the overtaking vessel. Rule 15: in a crossing between two power-driven vessels, the one that has the other on her own starboard side. Rule 18(a) to (c): between vessels of different kinds — for example, a power-driven vessel underway keeps out of the way of a sailing vessel.
Is there a give-way vessel in a head-on situation?
Rule 14 does not direct either vessel to keep out of the way. Under Rule 14(a), two power-driven vessels meeting end-on or nearly so, with risk of collision, both alter to starboard and pass port to port. As we read it, there is no give-way and no stand-on vessel head-on — both act. Rule 8 still governs what that action looks like: positive, in ample time, and large enough to be readily apparent.
Is 'keep out of the way' the same as 'not impede'?
No. Rule 16 is about the duty to keep out of the way. A duty not to impede another vessel — Rule 9(b) in a narrow channel, Rule 10(j) in a traffic lane, or the duty in Rule 18(d) to avoid impeding a vessel constrained by her draught — is a different duty, and Rule 8(f) governs it: take early action to leave sufficient sea room, and that obligation is not lifted if risk of collision develops.
Early and substantial — read with Rule 8
What does 'early and substantial action' mean?
Rule 16 gives no time, range or number of degrees. Rule 8, which applies to any action to avoid collision, fills it in. The action must, if the circumstances of the case admit, be 'positive, made in ample time' (8(a)). An alteration of course or speed must be large enough to be 'readily apparent' to another vessel observing visually or by radar, and a succession of small alterations should be avoided (8(b)). And the action must result in passing at a safe distance, with its effectiveness checked until the other vessel is finally past and clear (8(d)).
In practice, early means acting while there is still plenty of room and before the other vessel has any reason to doubt you. Substantial means an alteration she notices at once — a clear change in your aspect or your lights by eye, a plain change in your track on her radar plot — not a few degrees she might miss.
Why does acting early matter so much to the other vessel?
Because of Rule 17. The stand-on vessel must keep her course and speed (17(a)(i)), but she may act on her own once it becomes apparent to her that the give-way vessel is not taking appropriate action (17(a)(ii)), and she must act when collision can no longer be avoided by the give-way vessel alone (17(b)).
In practice, a late or small alteration is exactly what can make the stand-on vessel conclude you are not acting. If she then manoeuvres at the same moment you do, the two actions can cancel each other out. Early, obvious action keeps her standing on.
Should the give-way vessel alter course or slow down?
Rule 8 allows either, or both. Rule 8(c): with room to do it, a course alteration on its own may be the most effective way to avoid a close-quarters situation, if it is made in good time, is substantial and does not create another one. Rule 8(e): if necessary, or to buy time to assess the situation, slow down, or stop or go astern.
In a crossing, Rule 15 adds that the give-way vessel shall, if the circumstances of the case admit, avoid crossing ahead of the other. In practice that usually means a bold alteration to starboard to pass astern of her, a substantial reduction of speed, or both. In our view a speed reduction you rely on should be a large one — it can take longer to show on the other vessel's radar than a bold alteration.
Do I need to sound a signal when I alter?
If you are a power-driven vessel underway and in sight of the other, yes. Rule 34(a) requires a manoeuvre authorised or required by the rules to be indicated on the whistle: one short blast for 'I am altering my course to starboard', two short blasts for 'I am altering my course to port', three short blasts for 'I am operating astern propulsion'. Rule 34(b) allows the same signals to be supplemented by flashes of light.
What does 'so far as possible' allow?
As we read it, it recognises that sea room, depth, other traffic or your own vessel's handling may limit what you can do. It does not excuse a late or small action when an early, bold one was available.
When can the give-way vessel resume her course?
Not until the other vessel is finally past and clear: Rule 8(d) requires the action to be checked until then. For an overtaking vessel, Rule 13(d) says the same in its own terms — a later change in the bearing between the two does not make her a crossing vessel or relieve her of keeping clear until she is finally past and clear.
In the oral
How might Rule 16 come up in an MCA oral?
It may come up inside a crossing or overtaking scenario, as 'what do you do, and when?'. Examples of the kind of question to be ready for:
“A power-driven vessel is crossing from your starboard side on a steady bearing. What do you do, and when?”
“What does 'substantial' mean? How many degrees?”
“Why not make a series of small alterations?”
“You're meeting another power-driven vessel head-on. Which of you is the give-way vessel?”
“You've altered. When do you come back to your course?”
Where do candidates go wrong on Rule 16?
The common slips: quoting a number of degrees as if the rule gave one; small, repeated alterations; waiting to see what the other vessel does; crossing ahead in a crossing situation; altering without saying how the action will be checked; forgetting the whistle signal when altering in sight as a power-driven vessel; and calling a 'not to impede' duty a give-way duty.
