1.5 Action to Avoid Collision (Rule 8)

Rule 8 — How to Maneuver

Rule 7 tells you whether risk exists; Rule 8 tells you how to act on it. It applies to every avoiding maneuver regardless of which vessel you are, and its guiding theme is early, bold, and verified action.

8(a) — Positive, ample time, good seamanship

"Any action taken to avoid collision shall, if the circumstances of the case admit, be positive, made in ample time and with due regard to the observance of good seamanship."

• Positive — a definite, committed maneuver, not a tentative nudge.
• In ample time — early, while the vessels are still well apart, so the other operator has time to see and understand your move.
• Good seamanship — consistent with prudent practice (this ties back to Rule 2).

8(b) — Big enough to be obvious

"Any alteration of course and/or speed to avoid collision shall, if the circumstances of the case admit, 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."

This is one of the most frequently tested points in the whole module. A series of small 5-degree nudges is wrong: to a distant observer — and especially on their radar — small changes are invisible, so the other vessel cannot tell you are giving way. Instead make one large, unmistakable alteration (commonly 30 degrees or more) that clearly signals your intention.

8(c) — Course change alone, when there is room

"If there is sufficient sea room, alteration of course alone may be the most effective action to avoid a close-quarters situation provided that it is made in good time, is substantial and does not result in another close-quarters situation."

When you have open water, a bold turn is usually better than fiddling with the throttle, because a turn is easier for the other vessel to observe and it preserves your speed and steering control. The caveat: your turn must not simply trade one dangerous encounter for another with a third vessel.

8(d) — Pass at a safe distance and check the result

"Action taken to avoid collision shall be such as to result in passing at a safe distance. The effectiveness of the action shall be carefully checked until the other vessel is finally past and clear."

Maneuvering is not fire-and-forget. After you alter, you must keep taking bearings to confirm the situation is actually opening up. If your first action does not work, you must take further action.

8(e) — Slow down or stop

"If necessary to avoid collision or 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."

Reducing speed is a legitimate and sometimes best avoiding action — especially in restricted visibility or close quarters, where slowing buys you time to appraise. On a single-screw or twin-screw small vessel, going to neutral or astern can be decisive.

8(f) — The 'not to impede' clauses

Several rules require a vessel not to impede the passage of another (for example, a vessel under 20 meters in a narrow channel, or crossing a traffic lane). Rule 8(f) explains what "not to impede" means: such a vessel must take early action to allow sufficient sea room for the safe passage of the other vessel, and it is not relieved of that obligation if a risk of collision develops — at that point both vessels must comply with the steering rules. "Not to impede" is a duty to stay out of the way proactively, not a grant of privilege.

Worked Example: Bold Turn vs. Timid Nudges

You are the give-way vessel in a crossing situation with a mile of open water to starboard. Correct Rule 8 action: while still well apart, make one substantial alteration to starboard — say 45 degrees — hold it long enough that the other operator plainly sees your new aspect, then check by bearing that the range is opening before returning to course. Incorrect action: trimming your heading 5 degrees at a time hoping to sneak across; those nudges are invisible to the other vessel and violate 8(b). If space were tight instead, 8(e) would favor coming off the throttle to let the other vessel clear ahead.

Quick Do / Don't Summary

In restricted visibility these habits matter even more. Because you may detect a target only by radar and cannot see its aspect, the safe default is an early, generous alteration and, if needed, a reduction of speed to build a clear picture before committing — never a late, small change that the other vessel cannot resolve on its own radar.

Exam Framing

The two highest-yield Rule 8 facts are: (1) avoiding action should be large enough to be readily apparent and a succession of small alterations should be avoided; and (2) you may slacken speed or stop to avoid collision or to gain time to assess. Also remember the verification duty — check effectiveness until the other vessel is finally past and clear.