Stage 1: When the distance between two vessels is such that maneuvers by one would have no immediate effect on the other, there is no risk of collision and both vessels can move freely. If a risk of collision could develop under present courses and speeds, such as a “constant bearing, decreasing range” situation, the Rules will require an early and substantial action by change of course and/or speed.

“Maneuver out of misunderstanding”

Stage 2: A risk of collision arises when any maneuver affects another vessel. The Rules state that if there is any doubt, a risk is deemed to exist. Approaches are classified as Overtaking, Crossing, or Head-on, and specific Rules apply based on these situations. Each vessel can then be designated as Stand-on or Give-way based on their relative approach position and course. The Give-way vessel must slow, stop, yield, or pass behind the Stand-on vessel, who shall maintain course and speed to provide predictability for the Give-way vessel. Let’s not forget Rule 18 which prioritizes certain vessels’ restrictive maneuvering capabilities under a hierarchy or pecking order, for example, powerboats yield to sailboats.

First, identify which one of the three types of encountering situations apply, determined by the relative bearings, courses and speeds between the vessels.

• Rule 13 – Overtaking
• Rule 14 – Head-On
• Rule 15 – Crossing

Once the type of encounter (and vessel type within the “pecking order/hierarchy”) is identified, the Rules directing the actions of each vessel can then be determined.

• Rule 16 – Action by Give-way Vessel (Slow, stop, yield, pass astern; avoid, pass safely)
• Rule 17 – Action by Stand-on Vessel (Maintain course and speed; be predictable)
• Rule 18 – Responsibilities Between Vessels (pecking order i.e., Not under command, restricted in her ability to maneuver, power vessel, sailing vessel, etc.)

Initially, with the existing time and distance between vessels, a readily apparent change of course is preferred. (R8(c)) “If there is sufficient sea room, alteration of course alone may be the most effective action.” This is because any change of speed alone may be difficult, if not impossible to see, while a “readily apparent” change of course is, well, readily apparent.

The risk escalates during the approach advance and options become more limited due to the speed, traffic congestion, environmental conditions, natural hazards, and the vessel’s maneuvering capabilities and limitations, including draft, stopping and turning radius. The Funnel concept emphasizes the need for taking early and substantial action, avoiding small speed and course changes which may not be “readily apparent” to the other. Maneuvers must be early and big enough, so they are fully understood.

Operators must remember that while avoiding collision with vessel A, they must also beware of the effect of the maneuver on vessel B or C. Rule 8(c) directs the 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.”

“Half of preventing collisions is you knowing what you’re doing; the other half is to be sure that the other ship knows what you’re doing.”

Stage 3: Now in a close-quarters situation, each vessel must adhere to the Rules that apply to the roles assigned to each vessel as either Stand-on or Give-way as the situation dictates. By following the Rules with early maneuvers, close-quarters, immediate danger and collisions can be easily avoided. There is still time to maneuver within the Rules as the vessels’ gap continues to diminish.

Per Rule 17(a)(ii) the stand-on vessel “may take action by maneuver alone as soon as it becomes apparent…” the Give-way vessel “is not taking appropriate action in compliance with these Rules.” This means rudder action only; no decelerating ~ at least at this point. Courts have held that the Stand-on vessel can be held liable if rudder action is taken too early.

This maneuver happens before the vessels reach the point where they are in immediate danger of collision. Sound signals are used to communicate intentions and responses to each other within Rule 32 Maneuvering and Warning Signals.

Vessels being operated with Good Seamanship, will have the expectation that there may be an unexpected event, such as a natural hazard to navigation, or hull, steering or machinery failure on either vessel, or even that a medical emergency may suddenly afflict an operator. Good defensive driving provides a safety bubble, escape routes and contingencies. In our case, “Be Prepared” means ready to take the proper action if, and when needed.

Stage 4: Continued violations of the Rules by either or both vessels, for any reason, can lead to an Immediate Danger / In extremis situation. Once the vessels reach a position where collision cannot be averted by the Give-way vessel alone, it becomes not only the right, but also the express duty of the Stand-on vessel to take such action as will, in the judgment of her master or commanding officer, best aid to avoid collision, including departure from the Rules.

R17(b) When the Stand-on vessel “finds herself so close that collision cannot be avoided by the action of the give-way vessel alone, she shall take such action as will best aid to avoid collision”.

This departure from the Rules is also addressed under Rule 2(b), Responsibility, which not only authorizes and allows for, but may even require a departure from the Rules whenever necessary to avoid immediate danger posed by a danger of navigation or collision. At this point, whatever it takes to avoid collision becomes acceptable, barring another collision or grounding.

In extremis, meaning “at the point of death” in Latin, describes a situation where a collision can no longer be avoided solely by the actions of the give-way vessel alone; the danger is so immediate that it requires maneuvering by both vessels in their attempt to avoid collision.

Vessels are in extremis whenever the situation advances to the point where, because of the proximity of the vessels, adherence to the normal rules is reasonably certain to cause collision. It is only at this critical point that deviation from the Rules is permitted. Departing from the Rules prematurely may lead to a collision, which could be a violation if not justified. The burden of proof falls on the vessel claiming the departure was necessary. Both necessity and immediate danger must be present. R17(d) “This Rule does not relieve the give-way vessel of her obligation to keep out of the way.”

“Prudence is the assumption that things invariably go wrong; it is the ingrained ability of spatial awareness and the need for sea room, the likelihood that the person on the other bridge does not comprehend the collision rules and is mad, blind, or drunk.”