Safe Speed: What Rule 6 Actually Requires

What the rule requires

Every vessel shall at all times proceed at a safe speed so that she can take proper and effective action to avoid collision and be stopped within a distance appropriate to the prevailing circumstances and conditions 33 CFR §83.06. Two duties are joined in that one sentence, and the exam separates options on it: you must be able to act, and you must be able to stop. An option that offers only the stopping half is incomplete.

At all times is the trigger phrase, and it is the phrase most often missed. Nothing switches Rule 6 on. It is not conditioned on fog, on darkness, on traffic, or on being in a channel. The state of visibility appears in the rule as the first of six factors, not as the condition that brings the rule into force.

The rule fixes no speed and gives no formula. It sets a standard and then lists twelve factors — six for all vessels, six more for vessels with operational radar — introduced by the words shall be among those taken into account. That wording makes the list a floor, not a boundary.

The six factors for every vessel

By all vessels COLREGs Rule 6(a):

State of visibility
Traffic density, including concentrations of fishing vessels or any other vessels
Maneuverability of the vessel, with special reference to stopping distance and turning ability in the prevailing conditions
At night, the presence of background light such as from shore lights or from back scatter of her own lights
State of wind, sea and current, and the proximity of navigational hazards
Draft in relation to the available depth of water

The mnemonic in general circulation is Very Dry Martinis Lay Willie Down — Visibility, Density of traffic, Maneuverability, Lights (background), Wind/sea/current, Draft. It gets you the six openings under pressure, and it is lossy in two places worth patching now: Willie also carries the proximity of navigational hazards, and Martinis means specifically stopping distance and turning ability, which is what a distractor about hull form or horsepower will fail to say.

You are on a 24-foot open skiff with no electronics, running a river at 2100 in clear weather. How many of the Rule 6(a) factors are you required to take into account?

All six. Rule 6(a) binds every vessel with no equipment qualification and no visibility threshold. Background light is live because it is night, and the shore lights along the bank plus the back scatter of your own lights are exactly what subparagraph (iv) names.

The six additional factors with operational radar

The trigger for the second list is operational radar COLREGs Rule 6(b), and the operative word for exam purposes is Additionally. These six are added to the first six; they do not stand in place of them.

Characteristics, efficiency and limitations of the radar equipment
Constraints imposed by the radar range scale in use
Effect on radar detection of sea state, weather and other sources of interference
The possibility that small vessels, ice and other floating objects may not be detected at an adequate range
Number, location and movement of vessels detected by radar
The more exact assessment of visibility that may be possible when radar is used to determine the range of vessels or other objects in the vicinity

Read that list as what it is: a catalogue of what radar will not tell you. Four of the six describe the set's limits. Only the last two describe information gained.

Regime

33 CFR §83.06 is the Inland text, and Inland Rule 6 is word-for-word identical to COLREGs Rule 6 COLREGs Rule 6. A safe-speed question gains nothing from its regime label. If a candidate is burning time deciding whether the stem said International, that time is wasted on this topic.

Telling it apart: 6(a) against 6(b)

One criterion divides the twelve factors: whether the vessel has operational radar.

Rule 6(a) — by all vessels. Six factors, binding whether or not anything is fitted at the helm COLREGs Rule 6(a). Most often misfiled: the state of visibility, which candidates hand to the radar list because they associate visibility with radar work. It is the first factor of the universal list and applies to a rowing skiff.
Rule 6(b) — additionally, by vessels with operational radar. Six further factors on top of the first six COLREGs Rule 6(b). Most often misfiled: the more exact assessment of the visibility that may be possible when radar is used to determine the range of vessels or other objects in the vicinity, which reads like a restatement of 6(a)(i). Sort it by the word range. If the option mentions using radar range to judge visibility, it belongs to the radar list.

The sorting test that settles almost every one of these: does the factor mention radar, or the equipment, or contacts, or ice and small floating objects? Then it is 6(b). Everything else on the list is 6(a).

Working a question

A 46-foot inspected passenger vessel, 3.5-foot draft, is inbound at 2130 down a buoyed channel toward an inlet. Visibility is two miles in haze. A commercial waterfront lies behind the channel marks. Radar is on and set to the half-mile scale. The ebb is setting across the channel at the bend, charted depth outside the channel edge is six feet at low water, and a dozen small craft are anchored fishing the ebb near the second bend.

Fix the regime and dispose of it. Inland waters, so 33 CFR §83.06 governs 33 CFR §83.06. The determination would be no different offshore, since the texts are identical.
Confirm the rule is in force. It is. At all times. Two miles of visibility does not suspend Rule 6, and neither would ten.
Run the six universal factors in order. Visibility: two miles in haze, degraded but usable. Traffic density: a concentration of small craft fishing, which the rule names by category. Maneuverability: what is this hull's stopping distance and turning ability tonight, with the ebb on her, not on a flat day. Background light: the waterfront loom will wash out the channel lights, and your own deck and running lights add back scatter. Wind, sea and current: the cross-set at the bend, plus the proximity of the channel edge as a navigational hazard. Draft against depth: 3.5 feet in a six-foot charted depth outside the line of buoys leaves very little, so a set out of the channel is a grounding, not an inconvenience.
Add the radar factors, because the set is operational. The half-mile scale is a constraint you chose: contacts beyond it are not on your screen. Sea state and rain in the haze will fill the picture with clutter. The anchored skiffs are small, wooden or inflatable in places, and may not paint at adequate range COLREGs Rule 6(b). Count and track what does paint. Use the range to a known mark to firm up your visibility estimate.
Apply the standard, which is the actual answer. Set the speed at which you can both take proper and effective action and be stopped within a distance appropriate to these conditions. Since the fishing fleet may not appear on radar until close, that distance is short, and the speed follows from it.
Now separate the options. A distractor giving a figure in knots fails, because Rule 6 states no figure. A distractor saying the radar permits maintaining speed fails against the very factors in 6(b). The surviving option either restates the standard or names one of the twelve factors.

Same vessel, same channel, but the radar is down for repair and tagged out. Which factors are you required to take into account?

The six under Rule 6(a). Rule 6(b) opens with "Additionally, by vessels with operational radar," so a set that is not operational brings nothing additional in. The determination of safe speed does not relax; the loss of the picture is itself a prevailing condition bearing on the distance in which you must be able to stop.

Where candidates lose the point

Treating safe speed as a restricted-visibility requirement. The topic is taught next to fog, so candidates reach for options that condition the duty on reduced visibility. The text reads at all times, and visibility is one factor of six.

Hunting for a number. A stem asking for the safe speed in a given situation attracts the option carrying a figure, because a figure looks like an answer. Rule 6 contains no speed, no limit and no arithmetic. The correct option will describe a capability: proper and effective action, and stopping within an appropriate distance.

Reading the list as closed. Shall be among those taken into account means the twelve are the minimum. An option naming a condition that does not appear verbatim in the rule is not wrong on that ground alone.

Giving a radar-equipped vessel only the radar factors. Candidates see "Additionally, by vessels with operational radar" and read the two lists as alternatives keyed to equipment. They are cumulative. A vessel with operational radar owes all twelve.

Reading radar as permission. Answers along the lines of "with radar operating you may maintain speed" pick up candidates who have run a set in poor visibility and trust it. Rule 6(b) lists the possibility that small vessels, ice and other floating objects may not be detected at an adequate range, and the degradation of detection by sea state, weather and interference. The rule catalogues the set's limits as factors reducing your safe speed.

Misreading background light as your own navigation lights. The factor is broader: shore lights or the back scatter of her own lights, and it applies at night COLREGs Rule 6(a). A question set on a lit waterfront at 2300 is testing that subparagraph.

Check yourself

You are 40 miles offshore in clear weather, visibility ten miles, no contacts anywhere on the horizon. Are you required to proceed at a safe speed?

Yes. Every vessel shall at all times proceed at a safe speed. There is no visibility threshold, traffic threshold or proximity threshold that brings Rule 6 into force, because it never leaves force. Both International and Inland.

Which of these must be taken into account by a vessel that has no radar: the constraints imposed by the radar range scale in use; the draft in relation to the available depth of water; the effect of sea state on radar detection; the number and movement of vessels detected by radar?

The draft in relation to the available depth of water. It is the sixth factor of Rule 6(a), which applies to all vessels. The other three sit in Rule 6(b) and are owed additionally by vessels with operational radar.

Your radar is operating and well tuned. Are you still required to take the state of visibility into account in determining safe speed?

Yes. Rule 6(b) begins with "Additionally," so its six factors are added to the six of Rule 6(a) rather than substituted for them. A vessel with operational radar considers all twelve.

Which statement matches the standard in the rule: you must be able to stop within half the distance of visibility; you must be able to stop within a distance appropriate to the prevailing circumstances and conditions; you must be able to stop within your own length?

Stopped within a distance appropriate to the prevailing circumstances and conditions. The other two are figures nobody wrote into the rule. Half-visibility rules of thumb circulate in wheelhouses and will appear as distractors precisely because they sound seamanlike.

A question on the safe-speed factors is labelled "(International Only)." You are sitting the Inland module. Does the answer change?

No. Inland Rule 6 is word-for-word identical to COLREGs Rule 6. Answer it without regard to the label and move on.

A candidate answers that Rule 6 requires you to be able to stop within an appropriate distance, full stop. What has been left out?

The other half of the standard: you must also be able to take proper and effective action to avoid collision. Both capabilities are required at the speed you are making, and an option offering only one of them is the near-miss distractor on this question.

Running a narrow buoyed channel at night, you have 18 inches of water under the keel and a beam-on ebb. Which two of the six universal factors are doing the most work?

Draft in relation to the available depth of water, and the state of wind, sea and current together with the proximity of navigational hazards. Both are named in Rule 6(a). A grounding question and a collision question are answered by the same rule here, since the channel edge is the hazard the current is setting you toward.