Rule 7 — Risk of Collision

TL;DR — Every vessel must use all available means to determine whether a risk of collision exists; if any doubt remains, that risk shall be deemed to exist. A steady compass bearing on an approaching vessel is the primary indicator that risk of collision is present. 33 CFR §83.07

---

What the Rule Says

Rule 7 is codified at 33 CFR §83.07 and establishes the affirmative duty every vessel carries to assess collision risk. The rule has four operative paragraphs.

Paragraph (a) — The universal duty and the doubt standard. Every vessel shall use all available means appropriate to the prevailing circumstances and conditions to determine if risk of collision exists. The rule then states the most important default: if there is any doubt, such risk shall be deemed to exist. 33 CFR §83.07

This is not permissive language. "Shall" is mandatory. The mariner does not get to weigh probabilities and conclude that a collision is unlikely; the moment doubt arises, the rule treats the risk as confirmed and the vessel's obligations under the steering and sailing rules are triggered.

Paragraph (b) — Radar obligations. Proper use shall be made of radar equipment if fitted and operational. "Proper use" includes two specific techniques: long-range scanning to obtain early warning of risk of collision, and radar plotting or equivalent systematic observation of detected objects. 33 CFR §83.07

Note the qualifier: "if fitted and operational." A vessel without radar, or with a radar that is inoperative, is not in violation of paragraph (b) for failing to use it. However, that vessel still carries the full paragraph (a) obligation to use all available means — which will then be limited to visual and auditory observation. 33 CFR §83.07

"Radar plotting or equivalent systematic observation" is the key phrase for exam purposes. A single radar observation is not sufficient. The rule requires a time-series of observations — a plot — so that the closest point of approach (CPA) and time to CPA can be derived. A single bearing or range snapshot is exactly the kind of scanty information paragraph (c) prohibits relying upon.

Paragraph (c) — The prohibition on scanty information. Assumptions shall not be made on the basis of scanty information, especially scanty radar information. 33 CFR §83.07

This paragraph directly reinforces paragraph (b). One radar contact does not establish a trend. One visual bearing does not confirm the bearing is steady or changing. The mariner must gather sufficient data before concluding that risk does or does not exist.

Paragraph (d) — Specific indicators of risk. Two considerations are enumerated, though the rule states these are "among those taken into account," meaning the list is not exhaustive.

First: risk of collision shall be deemed to exist if the compass bearing of an approaching vessel does not appreciably change. 33 CFR §83.07 This is the classic constant-bearing, decreasing-range (CBDR) scenario. If you take successive compass bearings on a vessel and the bearing remains steady while the vessel is getting closer, you are on a collision course.

Second: risk may sometimes exist even when an appreciable bearing change is evident, particularly when approaching a very large vessel or a tow, or when approaching a vessel at close range. 33 CFR §83.07 This is the exception that catches candidates off guard. A bearing that is changing does not automatically mean the situation is safe. A very large vessel or a tow occupies a large arc of bearing; even if the bearing to the bow is drawing forward, the bearing to the stern or to the tow may be drawing aft — meaning some part of the other vessel or its tow will still be in your path.

---

Why It Matters on the Exam

Rule 7 is tested heavily because it sits at the intersection of several other rules. Understanding it correctly requires understanding how it connects to the look-out rule and to the steering and sailing rules.

Connection to Rule 5 (Look-out). Rule 5 requires every vessel to maintain a proper look-out by sight and hearing as well as by all available means appropriate to the prevailing circumstances and conditions, so as to make a full appraisal of the situation and of the risk of collision. 33 CFR §83.05

The purpose stated in Rule 5 — "full appraisal of the situation and of the risk of collision" — is the predicate for Rule 7. You cannot comply with Rule 7 if you are not maintaining the look-out required by Rule 5. Exam questions sometimes present a scenario where a vessel fails to detect an approaching vessel at all; the correct analysis begins with Rule 5, then moves to Rule 7.

Connection to the steering and sailing rules. Rules 12, 16, and 17 all presuppose that risk of collision has been determined to exist. Rule 12 governs sailing vessel encounters when the vessels are approaching so as to involve risk of collision. 33 CFR §83.12 Rule 17 governs the stand-on vessel's obligations once the give-way/stand-on relationship is established — which itself only arises when risk of collision exists. 33 CFR §83.17

If a candidate cannot correctly identify when risk of collision exists under Rule 7, they will misapply every downstream rule. This is why Rule 7 is foundational.

The "any doubt" standard is absolute. Exam questions frequently present scenarios designed to test whether the candidate understands that the doubt standard eliminates discretion. Phrases like "the officer of the watch believed the situation was probably safe" or "the bearing appeared to be drawing slowly" are red flags. Under 33 CFR §83.07, any residual doubt triggers the deemed-to-exist standard. There is no "probably safe" category.

Radar plotting is mandatory, not optional. When radar is fitted and operational, paragraph (b) requires its proper use, including plotting or equivalent systematic observation. 33 CFR §83.07 A single radar observation — one range and bearing — does not constitute proper use. Exam questions may describe a watchstander who glances at the radar, notes a contact, and takes no further action. That is a Rule 7(b) violation.

The large vessel / tow exception. Paragraph (d)(ii) is a favorite exam topic because it is counterintuitive. Candidates who have memorized "steady bearing equals collision risk" sometimes assume the converse — that a changing bearing means no risk. The rule explicitly rejects that assumption for large vessels and tows. 33 CFR §83.07 When approaching a tow, the towing vessel's bearing may be drawing clear while the tow itself remains in your path.

---

Common Pitfalls

Pitfall 1: Confusing "compass bearing" with "relative bearing." Paragraph (d)(i) specifies compass bearing — a bearing referenced to compass north, not to your own vessel's heading. 33 CFR §83.07 A relative bearing can remain steady simply because your own vessel is turning. Only a steady compass bearing on an approaching vessel, combined with decreasing range, reliably indicates collision risk. Exam questions sometimes describe a scenario where the relative bearing is steady but the own vessel is altering course; the correct answer requires recognizing that compass bearing is the operative measure.

Pitfall 2: Treating the paragraph (d) list as exhaustive. The rule states these considerations "shall be among those taken into account." 33 CFR §83.07 The list is illustrative, not exhaustive. Risk of collision can exist for reasons not enumerated in paragraph (d). Candidates who treat the two listed indicators as the only indicators will miss scenarios where risk exists for other reasons.

Pitfall 3: Assuming an operational radar eliminates the need for visual look-out. Rule 7(b) requires proper use of radar if fitted and operational, but this is in addition to, not instead of, the all-available-means standard in paragraph (a) and the sight-and-hearing requirement in Rule 5. 33 CFR §83.07 33 CFR §83.05 Radar does not substitute for a visual watch.

Pitfall 4: Acting on a single radar observation. Paragraph (c) prohibits assumptions based on scanty information, especially scanty radar information. 33 CFR §83.07 One plot point establishes position, not motion. CPA and TCPA require at least two observations separated by a meaningful time interval. Acting — or failing to act — on a single radar observation is a Rule 7(c) violation.

Pitfall 5: Forgetting the deemed-to-exist default. The rule does not say risk of collision exists only when the bearing is steady. It says risk shall be deemed to exist if there is any doubt. 33 CFR §83.07 A slowly changing bearing, a contact at close range, or any ambiguous situation triggers the default. Candidates who wait for certainty before acting are applying the wrong standard.

---

Quick Check

Q1: Under Rule 7, when is risk of collision deemed to exist?

Risk of collision shall be deemed to exist if there is any doubt as to whether such risk exists. Additionally, risk shall be deemed to exist if the compass bearing of an approaching vessel does not appreciably change. 33 CFR §83.07

Q2: Your vessel is fitted with an operational radar. What specific actions does Rule 7 require you to take with it?

You must make proper use of the radar, which includes long-range scanning to obtain early warning of risk of collision, and radar plotting or equivalent systematic observation of detected objects. A single observation does not satisfy the plotting requirement. 33 CFR §83.07

Q3: You are observing an approaching vessel and notice the compass bearing is slowly drawing forward. Does this mean risk of collision does not exist?

Not necessarily. While a steady compass bearing indicates risk of collision, an appreciable bearing change does not guarantee safety. Risk may still exist when approaching a very large vessel or a tow, or when approaching a vessel at close range. 33 CFR §83.07

Q4: What is the danger of relying on a single radar observation to assess collision risk?

Rule 7(c) prohibits making assumptions on the basis of scanty information, especially scanty radar information. A single observation establishes only position, not the contact's course, speed, CPA, or TCPA. Rule 7(b) requires plotting or equivalent systematic observation — meaning multiple observations over time. 33 CFR §83.07

Q5: What rule establishes the look-out requirement, and how does it relate to Rule 7?

Rule 5, codified at 33 CFR §83.05, requires every vessel to maintain a proper look-out by sight and hearing as well as by all available means appropriate to the prevailing circumstances and conditions, specifically to make a full appraisal of the situation and of the risk of collision. 33 CFR §83.05 Rule 7 then prescribes how that appraisal is to be made and what standard governs the determination of risk. Compliance with Rule 7 is impossible without first satisfying Rule 5. 33 CFR §83.07

Q6: You are approaching a vessel towing a barge on a long hawser. The bearing to the towing vessel is drawing slowly to starboard. Are you clear of all danger?

Not necessarily. Rule 7(d)(ii) specifically identifies tows as a situation where risk of collision may exist even when an appreciable bearing change is evident. The bearing to the towing vessel may be drawing clear while the tow itself remains in your vessel's path. You must assess the entire tow, not just the towing vessel. 33 CFR §83.07