1.5 Action to Avoid Collision (Rule 8)
Key Takeaways
- Rule 8 requires avoiding action to be positive, made in ample time, and taken with due regard to good seamanship.
- Any alteration of course and/or speed must be large enough to be readily apparent by eye or radar; a succession of small alterations should be avoided.
- With sufficient sea room, a bold course change alone is often most effective, provided it does not create another close-quarters situation.
- Action must result in passing at a safe distance, and effectiveness must be checked until the other vessel is finally past and clear.
- If necessary to avoid collision or gain assessment time, slacken speed or take all way off by stopping or reversing propulsion.
Why Rule 8 Owns the High-Stakes Module
On the ONC06 Master Less Than 100 GRT exam, Q100 Rules of the Road is scored at 90%. Knowing that risk of collision exists (Rule 7) is not enough; you must know how a lawful avoiding maneuver is executed. Rule 8 is that execution standard. It applies whether you are give-way or stand-on taking late action, power-driven or sailing, International or Inland. For a Master of a passenger-carrying vessel — day-charter, dinner cruise, water taxi under 100 GRT — the practical bar is higher than pure theory: your maneuver must be obvious to commercial traffic, small craft, and radar observers, and it must leave passengers and crew clear of a developing close-quarters problem.
Rule 8 is organized as a sequence of requirements that examiners reverse into discrete fact questions. Master them as an ordered checklist rather than a vague "be careful."
8(a) — Positive, Early, Good Seamanship
Rule 8(a) requires that any action to avoid collision shall, if circumstances admit, be positive, made in ample time, and taken with due regard to the observance of good seamanship.
- Positive means committed and unambiguous — not a half-degree wander while you "see what they do."
- Ample time means early enough that the other vessel can detect, understand, and respond to your intention while range still allows safe recovery.
- Good seamanship ties Rule 8 to Rule 2: a technically legal but reckless move (for example, a sharp turn into a third vessel's track) fails the rule even if it briefly increases CPA with the first target.
On a 65-foot inspected passenger vessel running a harbor tour, "ample time" is measured in minutes and thousands of yards, not in last-second helm. Waiting until the other vessel fills the windshield is an automatic fail in both real life and the exam bank.
8(b) — Large Enough to Be Readily Apparent
Rule 8(b) is the most tested clause in this section:
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.
A string of 5° nudges fails for two reasons. First, the other watchstander may not notice them by eye, especially at night or against a busy skyline. Second, on radar the track history of small successive changes looks noisy rather than intentional, so the other vessel cannot confidently predict your path. One bold alteration — often on the order of 30° or more when sea room allows — advertises intention. Pair the turn with a whistle signal when required by Rule 34 so the visual/radar picture and the sound signal tell the same story.
8(c) — Course Alone When Sea Room Exists
If there is sufficient sea room, alteration of course alone may be the most effective action to avoid a close-quarters situation, provided the turn is in good time, substantial, and does not result in another close-quarters situation.
Why course over speed when open water is available? A heading change is usually easier for the other vessel to detect by aspect and by radar trail; you keep steerage way and engine responsiveness; and you resolve geometry quickly if you pass well clear. The non-negotiable caveat: do not "solve" Vessel A by driving yourself into Vessel B. On a multi-vessel Sunday afternoon off a popular marina, the Master must scan the whole picture before committing the helm.
8(d) — Safe Distance and Continuous Check
Action must 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.
Safe distance is context-dependent: open coastal water differs from a buoyed approach channel with passenger decks full. The exam emphasis is the duty to verify. After you alter, continue plotting or taking relative bearings. If the bearing stabilizes again or CPA collapses, you have not finished acting — take further action. "I turned once" is not a complete Rule 8 performance.
8(e) — Slacken, Stop, or Reverse
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.
Speed reduction is not a last resort reserved for fog; it is a primary tool whenever early assessment or a controlled pass requires it. Taking all way off can include neutral, reverse, and — on twin-screw passenger craft — using engines to kill residual headway quickly. In a fog bank at the harbor entrance with a radar target forward of the beam whose aspect is unclear, Rule 8(e) plus Rule 19 favor reducing speed until the situation is clear rather than guessing a turn.
8(f) — "Not to Impede" Explained
Several rules (notably Rules 9 and 10) require certain vessels not to impede the passage of others. Rule 8(f) clarifies that duty:
- The vessel required not to impede shall, when required by the circumstances of the case, take early action to allow sufficient sea room for the safe passage of the other vessel.
- That vessel is not relieved of this obligation if risk of collision develops; when risk of collision exists, both vessels must comply with the applicable steering and sailing rules.
"Not to impede" is a proactive clearance duty, not a shield that freezes the other vessel into a permanent stand-on status if a collision risk actually forms. A 48-foot Master 100 passenger boat under 20 meters in a narrow ship channel must leave sea room for a deep-draft freighter early; if risk later develops anyway, both vessels still have Rule 8/16/17 duties.
Master Scenario: Harbor Ferry Crossing Ahead
You command an 85-foot passenger vessel on a COI day trip. A commercial ferry appears fine on the starboard bow with a steady compass bearing (Rule 7 risk). You are give-way under Rule 15. Rule 8-correct action: while still well apart, make one substantial starboard alteration large enough that your new aspect is obvious by day and by radar, aim to pass well astern, recheck bearings until the ferry is past and clear, and sound the required maneuvering signal. Rule 8-incorrect action: three timid 8° trims hoping to "ease across," or holding speed and cutting the bow. If the ferry's aspect remains unclear in haze, come off the throttle under 8(e) until the picture is reliable.
Rule 8 Action Checklist
| Clause | Requirement | Exam trap to avoid |
|---|---|---|
| 8(a) | Positive, ample time, good seamanship | Waiting until close quarters |
| 8(b) | Alteration readily apparent; no succession of small changes | Multiple tiny course/speed nudges |
| 8(c) | Bold course change alone if sea room; no new close-quarters | Turning into a third vessel |
| 8(d) | Pass at safe distance; check until past and clear | One-and-done without rechecking |
| 8(e) | Slacken, stop, or reverse to avoid collision or assess | Believing speed must never be reduced |
| 8(f) | Not-to-impede vessels create early sea room; both still bound if risk arises | Treating "not impede" as absolute privilege |
Exam Framing for Q100 (90%)
Highest-yield Rule 8 facts: alterations must be readily apparent and a succession of small alterations should be avoided; if needed, slacken speed or take all way off; check effectiveness until finally past and clear; and course alone is preferred only when there is sufficient sea room and the turn does not create another close-quarters situation. On Master exams these facts appear as pure rule language and as scenario stems with passenger vessels, ferries, and commercial traffic. Miss them and the 90% Rules module fails even if every other module is solid.
You are Master of a 72-foot passenger vessel and take action to avoid a ferry showing a steady bearing. Under Rule 8, which description best matches a lawful alteration of course or speed?
On your Master 100 passenger boat, a developing radar situation is unclear and collision risk may be forming. Under Rule 8, what may you do to allow more time to assess?
With open water available, you elect to avoid a close-quarters situation by course change alone. What additional Rule 8 condition must that course change meet?