Official rule text as published in the U.S. Coast Guard Navigation Rules
(a) Every vessel shall use all available means appropriate to the prevailing circumstances and conditions to determine if risk of collision exists. If there is any doubt such risk shall be deemed to exist.
(b) Proper use shall be made of radar equipment if fitted and operational, including long-range scanning to obtain early warning of risk of collision and radar plotting or equivalent systematic observation of detected objects.
(c) Assumptions shall not be made on the basis of scanty information, especially scanty radar information.
(d) In determining if risk of collision exists the following considerations shall be among those taken into account:
(i) Such risk shall be deemed to exist if the compass bearing of an approaching vessel does not appreciably change.
(ii) Such 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.
MyCOLREGS explanation
Summary
Rule 7 requires using all available means to determine whether risk of collision exists, and if there is any doubt, you must treat the risk as real. Proper use must be made of radar if fitted and operational, including plotting or equivalent systematic observation - but Rule 7(c) is equally direct: assumptions shall not be made on the basis of scanty information, especially scanty radar information. The same caution applies to any electronic aid, AIS included - a missing, delayed, or absent AIS target does not mean there is no vessel there, and a target that has AIS can still maneuver in ways the data does not predict. Rule 7(d)(i) gives the classic warning sign: if the compass bearing of an approaching vessel is not appreciably changing, risk of collision is deemed to exist - even before the vessels are close. A steady bearing with closing range is the geometry of a potential collision, not a coincidence.
Real World Example
A constant bearing is dangerous precisely because it's easy to miss - the eye readily catches a vessel angling across your bow but is bad at noticing one holding a fixed angle while closing, so by the time the danger looks obvious the range for a comfortable maneuver may already be gone. The same caution applies to electronics: most recreational boats aren't required to carry AIS, and even where it's fitted, a skipper can switch it off - so a chartplotter that looks clear is really only showing you the vessels that chose to be seen, not the vessels that are actually out there.
Practice Questions
Q1. A vessel off your port bow has stayed at roughly the same compass bearing for several minutes while steadily getting closer. Under Rule 7(d)(i), what should you conclude?
A. Risk of collision is deemed to exist, because the compass bearing of an approaching vessel is not appreciably changing.
B. Risk of collision only exists once the two vessels are within one mile of each other.
C. Nothing — a steady bearing means the vessel will pass safely astern.
D. You should only be concerned if the vessel is on your starboard side.
Q2. Your chartplotter shows no AIS targets nearby, but you visually spot a vessel's running lights ahead. What does Rule 7 suggest you should trust?
A. Neither, until the target also appears on radar, since Rule 7 treats radar as the primary means of detection and visual sightings as unreliable without electronic confirmation.
B. The AIS display, since it is the more modern technology and Rule 7 favors electronic means over a lookout's own eyes whenever both are available.
C. The AIS display exclusively, and disregard the visual sighting as a false contact, since a properly functioning AIS system would show every real vessel operating nearby.
D. Both — but per Rule 7(a) and (c), you must use all available means and not build assumptions on scanty information, so the visual sighting cannot be dismissed just because AIS is silent.
Practice Question Answers
Q1.
A. Risk of collision is deemed to exist, because the compass bearing of an approaching vessel is not appreciably changing. Rule 7(d)(i) states that risk of collision shall be deemed to exist if the compass bearing of an approaching vessel does not appreciably change — a constant bearing with decreasing range is the classic collision-course signature. B invents a one-mile threshold the rule doesn't set. C gets the geometry backwards - a steady bearing with closing range is the classic collision indicator, not a sign of a safe pass. D makes it about which side, when the bearing test applies regardless of side.
Q2.
D. Both — but per Rule 7(a) and (c), you must use all available means and not build assumptions on scanty information, so the visual sighting cannot be dismissed just because AIS is silent. Rule 7(a) requires using all available means to determine collision risk, and Rule 7(c) warns against assumptions based on scanty information — an AIS gap does not override what you can see with your own eyes, since small or non-transmitting vessels routinely have no AIS signature. A adds an extra requirement the rule doesn't impose. B and C both make the mistake of trusting the electronic display over a direct visual sighting - exactly the "scanty information" trap Rule 7(c) warns against.