Collision Avoidance, Cones of Uncertainty, and Appropriate CPA

[Lodesman]

Originally Posted by markpierce

That is pathetic. PATHETIC! Other than during high-tide, I sound a loud, four-second blast on my horn when leaving the marina which is surrounded by a sea-wall blocking the view. ... I do plead guilty in not usually sounding three shorts when backing out of the berth.

It depends upon what side of Lake Ontario, Rod is on. While the inland rules require all power driven vessels to sound the departure signal, the Canadian rules only require it for PDVs greater than 12m long.

[StuM]

Originally Posted by El Pinguino

'Not getting sunk' really is the same as 'Preventing Collisions' as in 'International Regulations for Preventing Collisions at Sea' just expressed in a slightly different manner....

Really? That's all there is to it?

In that case, the recent US Destroyers were quite OK since they didn't get sunk - just killed dozens of sailors.

[El Pinguino]

Originally Posted by markpierce

That is pathetic. PATHETIC! Other than during high-tide, I sound a loud, four-second blast on my horn when leaving the marina which is surrounded by a sea-wall blocking the view. ... I do plead guilty in not usually sounding three shorts when backing out of the berth.

Sorry, but you can't cherry pick the rules like that...

[El Pinguino]

Originally Posted by StuM

Really? That's all there is to it?

In that case, the recent US Destroyers were quite OK since they didn't get sunk - just killed dozens of sailors.

Now you are just being foolish....

Preventing Collisions = don't sink the boat = don't kill anyone = don't bend the boat .... unless one is shooting for pedant of the year award - but I have to tell you competition is pretty heavy this year....

[Dockhead]

Originally Posted by ramblinrod

I am sure that there are many commercial mariners who wish there were no other vessels than the one they are in charge of on the water, and believe that everyone else out there is an idiot.

When one gets paid to do a job, they are likely to follow different procedures than one who is not. The one who is paid, must follow orders or direction of authority. The one who is not, just needs to satisfy their pucker factor.

I also know that some recreational sailors get way too anal about "proper vessel handling". For some, excessive obsession with collision avoidance and prudent seamanship may be "fun", for others, any more than required to not get sunk, is too much infringement on their freedom and relaxation.

I guess you fall into the former, and I fall in the latter category.

I would not go so far as to suggest either is right or wrong, just that it does take all kinds, to make the diverse boating community we all enjoy.

Yes, certainly, it does take all kinds, I agree completely, and different people care more and less about different aspects of our sport. But a what might seem to some like an "obsession" with some aspect of our sport (whether it's collision avoidance, or navigation, or sail trim, or electrical systems), might often just be a keen interest in the subject and eagerness to share some knowledge gained from effort put into studying it. So we have one kind of debate on here which is healthy - "it works like this, and here's why" "no, it works like that, and here's why". And we have another kind of debate, which seems to me is less healthy "it works like this, and here's why" "I don't care about that, and don't think you should care beither, and I'm going to poke you for blabbing on about it and prove that you've been wasting your time studying it." That leads to no where -- let people have their own enthusiasms, even if we don't consider them relevant to us personally.


As to what professionals think about us -- my sense of the culture among marine professionals is that the great majority are very serious about their mastery of the various skill sets they have, and are not disdainful of us just to be disdainful. I do not agree that there are a lot of different "right" ways to do collision avoidance -- there is ONE set of Rules, and the whole system doesn't work if we just make up our own. They do it all the same way and coordinate their maneuvers with each other, and they expect for us to follow the Rules and do it the same way. What they feel disdain for us about is the wilful ignorance many of us have about the Rules, and about how to behave in a crossing with a ship. I have a lot of sympathy for this point of view.

However, I also acknowledge that most cruisers do not actually ever get into a difficult collision avoidance situation with ships. Most cruisers never sail or hardly ever sail in open sea in heavy traffic. They either sail in lakes, bays, and approaches to harbors where you can clearly see where ships are going to go, and where you don't need any collision avoidance technique at all -- just stay out of the fairways and stay out of the way, job done. Or in open sea away from traffic lanes where you might have a difficult crossing only once in a blue moon.

I was like this myself for decades, not knowing the first thing about collision avoidance, until I started sailing in the English Channel eight years ago. Crossing the English Channel in a yacht has been compared to being a squirrel trying to run across a busy motorway. And I think my very first time across, I avoided one ship only to end up about to be run down by another, not knowing which way to turn or what to do, like a deer in the headlights (that was pre-AIS). I realized with a shock that I didn't understand jackshort about how to do collision avoidance, and set about learning it intensely, learning how it works and why. The next thing I understood was that I didn't understand jack about what was going on in the minds of the professionals on the bridges of the ships I was dodging, how they structure their maneuvers, at what distances they do it, what they expect from us. So I made contact and started interviewing commercial captains and bridge crew to try to understand. I got into this not so much because I thought I would die, if I didn't achieve complete mastery of the subject, but because I found the whole subject extremely interesting and enjoyable.

If I had never sailed in the English Channel, I would certainly still be doing it the way you do it (and the way my Father does it to this day), relying on the ship to create a safe pass when I occasionally bumble into one's way because I didn't understand the distance at which I needed to maneuver, or what kind of maneuver is required, doing nonsense like one degree course corrections and probably thinking that I do it just fine since I've never been run down yet.

As to testing your collision avoidance practices against "worst cases" -- of course you have to do this. What good is it otherwise? You don't need any skill, to get through an easy crossing, with an obvious aspect you can see with your bare eyes, so with an obvious maneuver. For that matter, most crossings with ships are not on a collision course at all -- you might as well sleep in your bunk and leave the boat on autopilot. But that doesn't mean that sleeping and autopilot is a reasonable way to do collision avoidance!!! Do you see? Likewise, just eyeballing the ship's aspect when he gets close enough, and jinking around if it doesn't look right, might actually work in the great majority of cases, but that doesn't make it good technique! If you care about doing collision avoidance right, your procedure should be aimed specifically at hard cases, at "worst cases". At the case, for example, where you find yourself on a collision course and not knowing which way to turn, or how much time you have. Otherwise, what's the point of it?

Or if you just don't care, that's ok too. I'm not anyone's mother! I'm not interested in persuading anyone who just doesn't want to know; there are plenty others who do! It's completely different, with someone who DOES care, but thinks that something I say is wrong, or thinks they have a better technique than something I have proposed. There's always, always something to learn, in such a discussion, without any regard to who is right and who, ultimately, is wrong.

[ramblinrod]

Originally Posted by Dockhead

Yes, certainly, it does take all kinds, I agree completely, and different people care more and less about different aspects of our sport. But a what might seem to some like an "obsession" with some aspect of our sport (whether it's collision avoidance, or navigation, or sail trim, or electrical systems), might often just be a keen interest in the subject and eagerness to share some knowledge gained from effort put into studying it. So we have one kind of debate on here which is healthy - "it works like this, and here's why" "no, it works like that, and here's why". And we have another kind of debate, which seems to me is less healthy "it works like this, and here's why" "I don't care about that, and don't think you should care beither, and I'm going to poke you for blabbing on about it and prove that you've been wasting your time studying it." That leads to no where -- let people have their own enthusiasms, even if we don't consider them relevant to us personally.

As to what professionals think about us -- my sense of the culture among marine professionals is that the great majority are very serious about their mastery of the various skill sets they have, and are not disdainful of us just to be disdainful. I do not agree that there are a lot of different "right" ways to do collision avoidance -- there is ONE set of Rules, and the whole system doesn't work if we just make up our own. They do it all the same way and coordinate their maneuvers with each other, and they expect for us to follow the Rules and do it the same way. What they feel disdain for us about is the wilful ignorance many of us have about the Rules, and about how to behave in a crossing with a ship. I have a lot of sympathy for this point of view.

However, I also acknowledge that most cruisers do not actually ever get into a difficult collision avoidance situation with ships. Most cruisers never sail or hardly ever sail in open sea in heavy traffic. They either sail in lakes, bays, and approaches to harbors where you can clearly see where ships are going to go, and where you don't need any collision avoidance technique at all -- just stay out of the fairways and stay out of the way, job done. Or in open sea away from traffic lanes where you might have a difficult crossing only once in a blue moon.

I was like this myself for decades, not knowing the first thing about collision avoidance, until I started sailing in the English Channel eight years ago. Crossing the English Channel in a yacht has been compared to being a squirrel trying to run across a busy motorway. And I think my very first time across, I avoided one ship only to end up about to be run down by another, not knowing which way to turn or what to do, like a deer in the headlights (that was pre-AIS). I realized with a shock that I didn't understand jackshort about how to do collision avoidance, and set about learning it intensely, learning how it works and why. The next thing I understood was that I didn't understand jack about what was going on in the minds of the professionals on the bridges of the ships I was dodging, how they structure their maneuvers, at what distances they do it, what they expect from us. So I made contact and started interviewing commercial captains and bridge crew to try to understand. I got into this not so much because I thought I would die, if I didn't achieve complete mastery of the subject, but because I found the whole subject extremely interesting and enjoyable.

If I had never sailed in the English Channel, I would certainly still be doing it the way you do it (and the way my Father does it to this day), relying on the ship to create a safe pass when I occasionally bumble into one's way because I didn't understand the distance at which I needed to maneuver, or what kind of maneuver is required, doing nonsense like one degree course corrections and probably thinking that I do it just fine since I've never been run down yet.

As to testing your collision avoidance practices against "worst cases" -- of course you have to do this. What good is it otherwise? You don't need any skill, to get through an easy crossing, with an obvious aspect you can see with your bare eyes, so with an obvious maneuver. For that matter, most crossings with ships are not on a collision course at all -- you might as well sleep in your bunk and leave the boat on autopilot. But that doesn't mean that sleeping and autopilot is a reasonable way to do collision avoidance!!! Do you see? Likewise, just eyeballing the ship's aspect when he gets close enough, and jinking around if it doesn't look right, might actually work in the great majority of cases, but that doesn't make it good technique! If you care about doing collision avoidance right, your procedure should be aimed specifically at hard cases, at "worst cases". At the case, for example, where you find yourself on a collision course and not knowing which way to turn, or how much time you have. Otherwise, what's the point of it?

Or if you just don't care, that's ok too. I'm not anyone's mother! I'm not interested in persuading anyone who just doesn't want to know; there are plenty others who do! It's completely different, with someone who DOES care, but thinks that something I say is wrong, or thinks they have a better technique than something I have proposed. There's always, always something to learn, in such a discussion, without any regard to who is right and who, ultimately, is wrong.

The entire first paragraph is a "straw man" argument.

You have set up a scenario of your own making, pretending it is someone else's, so that you can prepare an argument against that you feel you can win.

You even used quotations around the element you wished to argue against, that was no quotation at all. You just made it up.

Your position that one must always apply the same practices for less dire situations than worst possible scenarios is simply nonsense.

You have already agreed to this, and as anyone with any common sense should know, that one must be much more careful, allowing more room, crossing ahead or meeting head on, than crossing astern or leaving on a reciprocal course, and that one must exercise greater caution in congested high speed random traffic, than when crossing one ship on a known route.

And yet every time someone suggests a move for one scenario (or an undeclared one), you always revert to the worst possible scenario to declare their positon invalid and yours the only correct one.

That's just BS.

Again, you are setting up the argument parameters unilaterally, to make your argument plausible, which in many scenarios, it simply isn't.

Then you do acknowledge that practices in high traffic areas without TSS are likely different than those elsewhere, (but still declaring in other discussions that the same stringent practices should be used in all circumstances or one is a WAFI) and as I have objected, a CF moderator using this term and associating it with others, is very unbecoming.

Then you argue, "There is only one set of rules", as if this is your position alone and someone else disagrees. Another "strawman". Your post is simply full of it.

That's nonsense. There is no argument, and that has never been even implied anywhere in this thread, that there is anything but one set of rules, that set being colregs and all applicable legislation.

Again, nobody has argued against this, ever in this thread, yet you state this like it is your position alone against others.

My last post, indicated that the fervor and the policies and procedures with which one practices collision avoidance to comply with colregs, may vary, especially between professional vs recreational sailors, and yet both can be in total compliance.

You didn't address that at all. Why? You can't win an argument against that, because you know it is absolutely true and correct.

If one with little pucker factor determines a risk of collision has developed 1500 miles away, they are entitled to take action then. But one, with lesser pucker factor, determining that there is no risk of collision until a shorter distance away, is still correct, and there actions valid, as long as they don't collide, (or present a risk of collision) which is the entire thrust of colregs.

Neither is wrong, just different. Their approaches can be completely different, and yet totally compliant.

So yes, I do object very strongly to anyone who suggests, "Everyone must do it my way, always, the same way, or they are a f'n idiot."

[ramblinrod]

Originally Posted by Dockhead

Yes, certainly, it does take all kinds, I agree completely, and different people care more and less about different aspects of our sport. But a what might seem to some like an "obsession" with some aspect of our sport (whether it's collision avoidance, or navigation, or sail trim, or electrical systems), might often just be a keen interest in the subject and eagerness to share some knowledge gained from effort put into studying it. So we have one kind of debate on here which is healthy - "it works like this, and here's why" "no, it works like that, and here's why". And we have another kind of debate, which seems to me is less healthy "it works like this, and here's why" "I don't care about that, and don't think you should care beither, and I'm going to poke you for blabbing on about it and prove that you've been wasting your time studying it." That leads to no where -- let people have their own enthusiasms, even if we don't consider them relevant to us personally.


As to what professionals think about us -- my sense of the culture among marine professionals is that the great majority are very serious about their mastery of the various skill sets they have, and are not disdainful of us just to be disdainful. I do not agree that there are a lot of different "right" ways to do collision avoidance -- there is ONE set of Rules, and the whole system doesn't work if we just make up our own. They do it all the same way and coordinate their maneuvers with each other, and they expect for us to follow the Rules and do it the same way. What they feel disdain for us about is the wilful ignorance many of us have about the Rules, and about how to behave in a crossing with a ship. I have a lot of sympathy for this point of view.

However, I also acknowledge that most cruisers do not actually ever get into a difficult collision avoidance situation with ships. Most cruisers never sail or hardly ever sail in open sea in heavy traffic. They either sail in lakes, bays, and approaches to harbors where you can clearly see where ships are going to go, and where you don't need any collision avoidance technique at all -- just stay out of the fairways and stay out of the way, job done. Or in open sea away from traffic lanes where you might have a difficult crossing only once in a blue moon.

I was like this myself for decades, not knowing the first thing about collision avoidance, until I started sailing in the English Channel eight years ago. Crossing the English Channel in a yacht has been compared to being a squirrel trying to run across a busy motorway. And I think my very first time across, I avoided one ship only to end up about to be run down by another, not knowing which way to turn or what to do, like a deer in the headlights (that was pre-AIS). I realized with a shock that I didn't understand jackshort about how to do collision avoidance, and set about learning it intensely, learning how it works and why. The next thing I understood was that I didn't understand jack about what was going on in the minds of the professionals on the bridges of the ships I was dodging, how they structure their maneuvers, at what distances they do it, what they expect from us. So I made contact and started interviewing commercial captains and bridge crew to try to understand. I got into this not so much because I thought I would die, if I didn't achieve complete mastery of the subject, but because I found the whole subject extremely interesting and enjoyable.

If I had never sailed in the English Channel, I would certainly still be doing it the way you do it (and the way my Father does it to this day), relying on the ship to create a safe pass when I occasionally bumble into one's way because I didn't understand the distance at which I needed to maneuver, or what kind of maneuver is required, doing nonsense like one degree course corrections and probably thinking that I do it just fine since I've never been run down yet.

As to testing your collision avoidance practices against "worst cases" -- of course you have to do this. What good is it otherwise? You don't need any skill, to get through an easy crossing, with an obvious aspect you can see with your bare eyes, so with an obvious maneuver. For that matter, most crossings with ships are not on a collision course at all -- you might as well sleep in your bunk and leave the boat on autopilot. But that doesn't mean that sleeping and autopilot is a reasonable way to do collision avoidance!!! Do you see? Likewise, just eyeballing the ship's aspect when he gets close enough, and jinking around if it doesn't look right, might actually work in the great majority of cases, but that doesn't make it good technique! If you care about doing collision avoidance right, your procedure should be aimed specifically at hard cases, at "worst cases". At the case, for example, where you find yourself on a collision course and not knowing which way to turn, or how much time you have. Otherwise, what's the point of it?

Or if you just don't care, that's ok too. I'm not anyone's mother! I'm not interested in persuading anyone who just doesn't want to know; there are plenty others who do! It's completely different, with someone who DOES care, but thinks that something I say is wrong, or thinks they have a better technique than something I have proposed. There's always, always something to learn, in such a discussion, without any regard to who is right and who, ultimately, is wrong.

The more I read this post, the more offended I get.

It is riddled with innuendo, like I don't want to know what I need to know, or I don't care.

If I didn't care, I wouldn't devote so much time to debating this issue.

Who suggested anyone should sleep to an autopilot and this is OK?

Just knock it off with the BS strawman arguments.

I vehemently disagree with this following quotation from your post.

"If you care about doing collision avoidance right, your procedure should be aimed specifically at hard cases, at "worst cases"."

That is just nonsense.

Nobody need apply the protocol for a "worst case" (say, heavy storm, no visibility, bare poles, vessel barely, or perhaps not even, under control, a hundred boats of various sizes within one square mile all going in different directions at different speeds), to a "best case" (crossing at 90 degrees, a similar sized vessel at 5 knots, on a clear day in a gentle breeze, while motoring).

The required procedures and the safe proximities are completely different, not only based on the conditions scenario, but on the skill of the sailor(s).

Some aren't safe at any speed or distance.

Other's are safe, even if close enough you can see the whites of their eyes.

[Exile]

Always learning from these Colregs debates, no matter how strident. Now whether I become educated enough to apply this learning responsibly out on the water is a different matter! Appreciate all the time & effort regardless.

Two observations, for whatever they're worth.

1. May have missed something but I've always assumed the "WAFI" reference derived from professional mariners on big ships identifying rookie mistakes by recreational mariners, and not a term used by anyone on the forum to label another poster personally. Maybe to reference one of their practices or techniques perhaps, but not themselves personally. The obvious analogy which comes to mind is professional truckers on the road with various derogatory labels for unsafe maneuvers by "4-wheelers".

2. Unlike the rules of the actual road, the Colregs amount to rules that are often "fixed" in their language but deliberately crafted to be flexible enough to allow for the almost infinite number of factual scenarios that can & do develop on the water. Unlike rules on the roadways, often times the rules out on the water can be counterintuitive. In the first instance a 4-wheeler is required but also instinctively knows to switch over to another lane -- or slow down/speed up depending on traffic -- to allow a big truck to merge onto the highway. Whereas an analogous scenario in open water might require a small sailing vessel to stand on (maintain their course & speed) to allow the large ship to get out of the way. Not exactly intuitive, which is exactly why so many recreational mariners unknowingly but instinctively just react by getting the hell out of the way.

An overly simplistic example for sure, but only used to illustrate the utility of setting up very specific factual scenarios before a debate ensues on the proper application of the Colregs. Oftentimes I get the sense that disagreements on threads like this are less about misunderstandings on how the Rules apply & more about misunderstandings on the specifics of the factual scenarios presented for debate.

Just an observation from the peanut gallery . . . .

[spsexton]

Originally Posted by ramblinrod

The more I read this post, the more offended I get.

It is riddled with innuendo, like I don't want to know what I need to know, or I don't care.

If I didn't care, I wouldn't devote so much time to debating this issue.

Who suggested anyone should sleep to an autopilot and this is OK?

Just knock it off with the BS strawman arguments.

I vehemently disagree with this following quotation from your post.



That is just nonsense.

Nobody need apply the protocol for a "worst case" (say, heavy storm, no visibility, bare poles, vessel barely, or perhaps not even, under control, a hundred boats of various sizes within one square mile all going in different directions at different speeds), to a "best case" (crossing at 90 degrees, a similar sized vessel at 5 knots, on a clear day in a gentle breeze, while motoring).

The required procedures and the safe proximities are completely different, not only based on the conditions scenario, but on the skill of the sailor(s).

Some aren't safe at any speed or distance.

Other's are safe, even if close enough you can see the whites of their eyes.

Good work dockhead and good observations. It's unclear to me why people get so bent out of shape on this topic, taking things personally, and devolving to childish posts. Best to take the high road.

[ramblinrod]

Originally Posted by spsexton

Good work dockhead and good observations. It's unclear to me why people get so bent out of shape on this topic, taking things personally, and devolving to childish posts. Best to take the high road.

When someone casts aspersions on a my character, I take it personally.

You may consider these tactics "high road"; whereas I consider them "under-handed".

Anyone can debate the position of another poster all they wish, and I am
Absolutely fine with that, but please, stop posting strawman arguments.

It is a childish tactic that is only intended to deflect attention away from the weakness of ones arguments toward the real position of the "person" being debated.

[james247]

Originally Posted by StuM

It's actually set out in COLREGs.

Rule 7 - Risk of Collision
...such risk shall be deemed to exist if the compass bearing of an approaching vessel does not appreciably change

Some one taught me even before I could read COLREGs was it was my responsibility to avoid collision. In more than 60 years in all manner of boats I have never hit or been hit. Unless your racing it takes less than a minute in you trip to slip under the stern of a ship doing 12 to 23 knots. I don't see what the issue is.

[Exile]

Originally Posted by james247

Some one taught me even before I could read COLREGs was it was my responsibility to avoid collision. In more than 60 years in all manner of boats I have never hit or been hit. Unless your racing it takes less than a minute in you trip to slip under the stern of a ship doing 12 to 23 knots. I don't see what the issue is.

That's because, assuming you're stand on per the Rules, your maneuvering transfers the "issue" onto the other vessel, not you. You're assuming that you've never been involved in a collision on account of your actions alone, where the reality is your actions have probably resulted in other vessels compensating for what amounts to potentially dangerous unpredictability to them. This is exactly what a universally applied set of rules like the Colregs attempts to avoid.

[Dockhead]

Originally Posted by ramblinrod

The entire first paragraph is a "straw man" argument.

You have set up a scenario of your own making, pretending it is someone else's, so that you can prepare an argument against that you feel you can win.

You even used quotations around the element you wished to argue against, that was no quotation at all. You just made it up.

Your position that one must always apply the same practices for less dire situations than worst possible scenarios is simply nonsense.

You have already agreed to this, and as anyone with any common sense should know, that one must be much more careful, allowing more room, crossing ahead or meeting head on, than crossing astern or leaving on a reciprocal course, and that one must exercise greater caution in congested high speed random traffic, than when crossing one ship on a known route.

And yet every time someone suggests a move for one scenario (or an undeclared one), you always revert to the worst possible scenario to declare their positon invalid and yours the only correct one.

That's just BS.

Again, you are setting up the argument parameters unilaterally, to make your argument plausible, which in many scenarios, it simply isn't.

Then you do acknowledge that practices in high traffic areas without TSS are likely different than those elsewhere, (but still declaring in other discussions that the same stringent practices should be used in all circumstances or one is a WAFI) and as I have objected, a CF moderator using this term and associating it with others, is very unbecoming.

Then you argue, "There is only one set of rules", as if this is your position alone and someone else disagrees. Another "strawman". Your post is simply full of it.

That's nonsense. There is no argument, and that has never been even implied anywhere in this thread, that there is anything but one set of rules, that set being colregs and all applicable legislation.

Again, nobody has argued against this, ever in this thread, yet you state this like it is your position alone against others.

My last post, indicated that the fervor and the policies and procedures with which one practices collision avoidance to comply with colregs, may vary, especially between professional vs recreational sailors, and yet both can be in total compliance.

You didn't address that at all. Why? You can't win an argument against that, because you know it is absolutely true and correct.

If one with little pucker factor determines a risk of collision has developed 1500 miles away, they are entitled to take action then. But one, with lesser pucker factor, determining that there is no risk of collision until a shorter distance away, is still correct, and there actions valid, as long as they don't collide, (or present a risk of collision) which is the entire thrust of colregs.

Neither is wrong, just different. Their approaches can be completely different, and yet totally compliant.

So yes, I do object very strongly to anyone who suggests, "Everyone must do it my way, always, the same way, or they are a f'n idiot."

Oh, brother.

I don't think there's much in here that can be engaged in discussion.

I would just say one thing -- all this about "winning arguments" is leading you down the wrong path. If that's what this is about, maybe you should be playing chess or doing something else which is explicitly competitive. That's not indeed what this is about.

For me, "winning" is successfully conveying an idea, or successfully receiving one. Successfully conveying and idea to someone who sincerely disagrees is best of all -- there is always learning to be found in disagreement, if one approaches it in the right way. This conversation is clearly a big, fat "fail" for me -- I lost. Despite a lot of effort, not a single idea got through, as far as I can tell.

So Rod, I lost. Does that mean you "won"?

[Dockhead]

Maybe we could get this back on topic.

Cockcroft writes about the "Four Stages of Collision Situation":


"When two vessels in sight of each other are approaching with no change of compass bearing, so that when there is risk of collision one of them is required to keep out of the way by a Rule from Section 11, there may be four stages relating to the permitted or required action for each vessel:

"1. At long range, before risk of collision exists, both vessels are free to take any action.

"2. When risk of collision first begins to apply the give-way vessel is required to take early and substantial action to achieve a safe passing distance and the other vessel must keep her course and speed.

"3. When it becomes apparent that the give-way vessel is not taking appropriate action in compliance with the Rules the stand-on vessel is required to give the whistle signal prescribed in Rule 34(d) and is permitted to take action to avoid collision by her maneuver alone, but a power-driven vessel must not alter course to port to avoid another power driven vessel crossing from her own port side. The give-way vessel is not relieved of her obligation to keep out of the way.

"4. When collision cannot be avoided by the give-way vessel alone the stand-on vessel is required to take such action as will best aid to avoid collision.

"The distances at which the various stages begin to apply will vary considerably. They will be much greater for high speed vessels involved in a fine crossing situation. For a crossing situation involving two power-driven vessels in the open sea it is suggested that the outer limit of the second stage might be of the order of 5 to 8 miles and that the outer limit for the third stage would be about 2 to 3 miles."



Cockcroft & Lameijer, 6th edition, page 114


You cannot do this effectively, if you don't understand the distance frames of these stages -- what is going on, on the bridge of the ship. Some important points (for open sea):

* By 8 miles out and no less than 5 miles, if not earlier, a ship crossing with you will consider that a fully developed risk of collision exists and he will maneuver at this point if not constrained by other traffic or some other circumstance, or will expect you to maneuver if you are give-way.

* If he is give-way and he hasn't maneuvered by 3 or 4 miles out, it is reasonable to conclude that he is not going to. Time to call him to find out his intentions, or maneuver yourself if you are stand-on. A potentially fatal misunderstanding many of us have, is to keep waiting until a mile (or less!) for him to maneuver. Ain't happening. That is beyond the range of that phase, for him. What is crucial to understand is what happens during this phase between 3 or 4 miles and 1 mile -- you are now free to maneuver, and you are obligated to get ready to do it. You must not just sail on waiting for him to maneuver.

* This varies with speed, and varies with the type of crossing, but if he is at sea speed, then by one mile off, options to prevent a collision are dwindling by the second. This is already in extremis -- Cockcroft's last stage. In open sea, you just should not be here. If you ever at all get within a mile of a fast moving ship in open sea, it should only be if you are clearly passing astern. Once you get within a mile and you have an unresolved collision course, there is no easy or safe way to unwind it.

Why? Let me count the ways:

1. Because you are in the fourth stage of maneuvering and both vessels are obligated to maneuver. So you by this time, you have lost the chance already to have coordinated maneuvering where one vessel stands on and the other takes control. Uncoordinated maneuvering -- probably "desperate maneuvering" would be the right word -- is much more dangerous because of the risk of two maneuvers of two ships conflicting with each other.

2. Once you are down to a few seconds, if you make a maneuver and it doesn't work, you won't have another chance. The Rules require

3. At some point (depending on the configuration of the ship), you can't be seen, either by sight or by radar, and the ship can no longer do anything to avoid you.

4. With a big difference in speed, your ability to get out of his way diminishes fast as you get closer.

So the interaction of 3 and 4 can be really deadly -- he can't see you and doesn't know where you are beneath his bows, and you can't get out of his way because you are too slow.

For all these reasons:

* Maintain an appropriate CPA

* Be aware of the stages of collision avoidance, and which one you are in.

[Juho]

Originally Posted by Dockhead

Maybe we could get this back on topic.

Cockcroft writes about the "Four Stages of Collision Situation":

...

This staged approach is good since it can explain many of the complexities of colregs in one simple framework that can be used by sailors also as a clear procedure to follow.

The length of each stage is an interesting question. I think the most important parameter that defines then is maybe the time to collision or TCPA. I.e. timing could be the same for all vessels, but distances would be longer for fast vessels.

Another parameter could be the smallest safe distance/time (margin) for manoeuvres. For large tankers with poor visibility forward the distance/time would be larger than for smaller vessels with same speed. The value of this parameter could depend also on the current speed of the vessel, but maybe better to keep it simple.

When two vessels with different speed meet, TCPA is the same for both vessels, but the smallest safe distance/time to manoeuvre may be different. I'll skip the detailed formulae to count times and distances for the different stages for now. Maybe something like the longer of the safe distances/times + some amount of TCPA for each stage.

It is possible that timing would be about the same for both in open waters and when in situations with some constraints. If there are multiple vessels, I guess timing can be often calculated separately for each pair of vessels.

Just some thoughts to feed up your thoughts.