Action to Avoid Collision — Making the Maneuver Big Enough, Early Enough, and Checking It

What the rule requires

Rule 8 does not tell you who gives way. It tells you what a lawful maneuver looks like once some other rule has told you to act, and that is where the exam questions live: the options on a Rule 8 question are all maneuvers, and the operative words separate them.

The maneuver must be large enough to be readily apparent to another vessel observing visually or by radar, and a succession of small alterations of course and/or speed should be avoided COLREGs Rule 8. Any answer option offering a gradual, incremental, or series-of-small-adjustments approach is eliminated by that single clause. The reason sits in the words "or by radar": a five-degree nudge does not develop on another vessel's plot until it is too late to be useful.

Having made the alteration, you are not finished. Action must result in passing at a safe distance, and the effectiveness of the action shall be carefully checked until the other vessel is finally past and clear. The rule fixes no CPA in miles and no time in minutes — there is no number to memorise here, which is precisely why the exam tests the wording instead.

Speed is an avoiding action in its own right. If necessary to avoid collision or to allow more time to assess the situation, a vessel shall slacken her speed or take all way off by stopping or reversing her means of propulsion. Those two triggers are separate: you do not need to have concluded that collision is imminent before you slow. Needing time to work out what is happening is sufficient grounds on its own.

Where there is sufficient sea room, alteration of course alone may be the most effective action to avoid a close-quarters situation, provided it is made in good time, is substantial, and does not result in another close-quarters situation. Three conditions ride on that permission, and the third is the one candidates drop: a bold turn that clears the ship ahead and puts you into a close-quarters situation with the tow on your beam is not compliance.

Underneath all of it, any action taken shall be positive, made in ample time and with due regard to the observance of good seamanship 33 CFR §83.08. "Good seamanship" is not decorative language; it is the hook into the requirement that nothing in the Rules exonerates a vessel or her master from the consequences of neglecting any precaution required by the ordinary practice of seamen COLREGs Rule 2.

You alter 30° to starboard for a crossing vessel and the range steadies at 1.2 miles with the bearing drawing slowly aft. May you come back to your original course?

No. Rule 8(d) requires the effectiveness of the action to be carefully checked until the other vessel is finally past and clear — not until the bearing starts to open, not until she is abaft the beam. Coming back early re-closes the CPA you just bought and does it at shorter range, where you have fewer options left.

International against Inland

Compare the two texts side by side and the operative requirements of Rule 8 are the same words in both regimes: positive action in ample time, alterations readily apparent visually or by radar, no succession of small alterations, passing at a safe distance, checking until past and clear, slackening or taking all way off. The divergence is confined to how each version cites its own rule set — the international text refers to "the Rules of this Part", the inland text to "the Rules of this subpart (Rules 4-19)" . Nothing you must do changes with the boundary. A Rule 8 question will normally be labelled "(Both International & Inland)", and you should not go looking for a trap that is not there.

Rule 8 also carries no requirement that the two vessels be in sight of one another. That condition belongs to Rule 11, which limits the rules in the section it opens — the crossing, give-way and stand-on rules — to vessels in sight COLREGs Rule 11. Rule 8 states no such precondition, so its standards govern your maneuver whether you are working a visual target or a radar contact you have never seen.

The "not to impede" provisions

Paragraph (f) is the part of Rule 8 candidates have not read, and it is worth the two minutes because it is written to defeat a specific wrong instinct.

• A vessel required by any rule not to impede the passage or safe passage of another shall, when required by the circumstances, take early action to allow sufficient sea room for the safe passage of the other vessel.
• That obligation is not extinguished when risk of collision develops. She remains bound by it, and when taking action must have full regard to what the steering and sailing rules require of her.
• The vessel whose passage is not to be impeded remains fully obliged to comply with those same rules once the two are approaching so as to involve risk of collision. Being the privileged party in a not-to-impede relationship buys you nothing once risk of collision exists.

Under the International Rules, the class most often on the receiving end of this is the vessel constrained by her draft: any vessel other than one not under command or restricted in her ability to maneuver shall, if circumstances admit, avoid impeding her safe passage, and the constrained vessel herself shall navigate with particular caution COLREGs Rule 18. On inland waters there is no such category — 33 CFR §83.18(d) is reserved 33 CFR §83.18. That is a live "(International Only)" answer and one of the cleaner marks on the module.

Telling it apart

The criterion that separates these three duties is what the duty is trying to achieve: to stop a close-quarters situation from ever forming, to keep clear of one that has, or to remain predictable while someone else keeps clear of you.

• Not to impede — the duty runs before risk of collision develops, and its content is early action to allow sufficient sea room COLREGs Rule 8. Most often misfiled as a give-way duty. It is not one: it does not by itself make you the give-way vessel in a crossing, and it does not lapse when risk of collision arises.
• Give-way — triggered by risk of collision in a defined encounter, and its content is early and substantial action to keep well clear COLREGs Rule 16. In a crossing of two power-driven vessels, the one with the other on her own starboard side keeps out of the way and, if circumstances admit, avoids crossing ahead COLREGs Rule 15.
• Stand-on — keep course and speed, with two escalating exceptions: she may maneuver alone as soon as it becomes apparent the give-way vessel is not taking appropriate action, and she shall take such action as will best aid to avoid collision when she finds herself so close that the give-way vessel alone cannot avoid it COLREGs Rule 17. Most often misfiled as a duty to hold on until the last moment. It is not, and the give-way vessel is not relieved of anything by the stand-on vessel acting.

One constraint on the stand-on vessel is tested repeatedly: a power-driven vessel taking action under 17(a)(ii) against another power-driven vessel shall not alter course to port for a vessel on her own port side.

Working a question

You are underway on a 78-foot passenger vessel, power-driven, making 12 knots in good visibility. A loaded product tanker is bearing 045 relative, range 5 miles, and over four minutes of radar observation her compass bearing has not appreciably changed. There is open water to starboard.

1. Establish whether risk of collision exists. The compass bearing is not appreciably changing, so risk shall be deemed to exist COLREGs Rule 7. Had the bearing been opening, you would still treat risk as existing, because she is a very large vessel — 7(d)(ii) names that case specifically.
2. Fix your status. Two power-driven vessels crossing with risk of collision, tanker on your starboard side: you are the give-way vessel, and you are additionally to avoid crossing ahead of her COLREGs Rule 15.
3. Choose the form of the action. You have sea room to starboard, so alteration of course alone is available and is the cleanest option, provided it is substantial and does not set up a second close-quarters situation with anything else on that side COLREGs Rule 8.
4. Size it. A single bold alteration to starboard, made now at 5 miles, so that it is unmistakable on the tanker's radar and to her lookout by eye. Not three successive 10° turns, and not a 5° trim followed by "we'll see how it looks".
5. Verify the result. Watch the bearing and range until she is finally past and clear, and be ready to slacken speed or take all way off if the CPA is not opening as intended.

Change one fact — your radar picture is incomplete and you cannot yet tell whether the contact ahead is one vessel or two. Then the answer is not a course alteration at all: assumptions shall not be made on the basis of scanty radar information, and Rule 8(e) authorises you to slacken speed or take all way off to allow more time to assess the situation.

Where candidates lose the point

• Picking "make a series of small course changes to open the CPA." It sounds like careful shiphandling, and on a busy bridge it is what tired people actually do. Rule 8(b) rules it out by name: the alteration must be readily apparent visually or by radar, and a succession of small alterations should be avoided.
• Picking "resume your original course once the other vessel is abaft the beam." Abaft the beam feels like clear. Rule 8(d) sets the standard at finally past and clear, and requires the effectiveness of your action to be checked, not assumed, up to that point.
• Answering that a vessel required not to impede is relieved of that duty once risk of collision develops. The candidate reasons that the steering rules must take over. Rule 8(f)(ii) says the obligation survives, and 8(f)(iii) puts the not-to-be-impeded vessel fully back under the steering rules at the same moment.
• Answering that the stand-on vessel may not reduce speed. "Keep her course and speed" gets read as an absolute. It is qualified by Rule 17(a)(ii) and 17(b), and Rule 8(e) is written for a vessel, without restriction to the give-way vessel.
• Altering to port for a vessel on the port bow when the give-way vessel does nothing. The turn away looks intuitive. Rule 17(c) forbids it for a power-driven vessel acting against another power-driven vessel in a crossing situation, if circumstances admit.
• Looking for a distance in Rule 8. Candidates hunt for a mile figure to attach to "safe distance" and then pick an option that supplies one. The rule fixes no distance; an option quoting a specific CPA as the Rule 8 requirement is manufactured.

Check yourself

You are the give-way vessel in a crossing situation, in open water with ample sea room, and the other vessel is 4 miles off on a steady bearing. Which action complies with Rule 8?

A single substantial alteration of course to starboard, made now, large enough to be readily apparent to her visually and on her radar, followed by monitoring until she is finally past and clear. Alteration of course alone is permitted because there is sufficient sea room and the turn is made in good time, so long as it does not create another close-quarters situation.

Your radar contact fine on the port bow is at 6 miles, the plot is incomplete, and you cannot yet tell whether risk of collision exists. What does the rule permit or require?

Treat risk as existing — if there is any doubt, such risk shall be deemed to exist, and assumptions are not to be made on scanty radar information. Rule 8(e) then allows you to slacken speed or take all way off by stopping or reversing your means of propulsion specifically to allow more time to assess the situation.

A vessel is required not to impede your passage. She is now approaching so as to involve risk of collision. What are your obligations?

You remain fully obliged to comply with the steering and sailing rules. Rule 8(f)(iii) is explicit that the vessel whose passage is not to be impeded gets no relief from those rules once risk of collision exists, and her failure to keep out of your way does not excuse your own non-compliance.

You are the stand-on power-driven vessel. The give-way vessel is on your port bow and plainly taking no action. May you alter course to port?

No. Rule 17(c) provides that a power-driven vessel acting under 17(a)(ii) against another power-driven vessel shall not, if circumstances admit, alter course to port for a vessel on her own port side. Alter to starboard, or reduce speed.

On inland waters, are you required to avoid impeding the safe passage of a vessel constrained by her draft?

No. 33 CFR §83.18(d) is reserved — the inland rules contain no vessel-constrained-by-draft category. The obligation to avoid impeding her, and her own duty to navigate with particular caution, exist under International Rule 18(d) only.

Fill the missing words: any action taken to avoid collision shall, if the circumstances of the case admit, be ______, made in ______ and with due regard to the observance of ______.

Positive; ample time; good seamanship. These three appear verbatim in both the international and inland texts of Rule 8(a), and questions built on them are typically labelled "(Both International & Inland)".

You made a 25° alteration for a crossing vessel ten minutes ago and have not looked at her since; the watch is otherwise quiet. What has gone wrong?

Rule 8(d) requires that the effectiveness of the action be carefully checked until the other vessel is finally past and clear. An alteration that was correct when made is not compliance on its own — if she has also maneuvered, or your CPA is not opening as intended, you have lost the sea room you bought and Rule 2 will not treat the omission kindly.