Collision Avoidance -- Dealing with Multiple Targets

[Juho]

Originally Posted by Pelagic

Something to consider is that one of the weaknesses of many juinior commercial officer's is their reluctance to make a large deviation from their prescribed course. For Fear of the Master questioning their efficiency.... Etc...

GPS accuracy has everyone in a tight zone of optimum but convergent tracks.

in a ML situation with large ships operating at higher speeds, if sea room is available I purposely and obviously take myself out of the equation with a 90° turn to Starboard, then a complete round turn as a delaying action before resuming course which is offset from the popular track.

I once got a salute from a captain of a large ship when I made that kind of a loop to a small bay after noticing the incoming ship at a really narrow strait. In that situation I had a plan B ready in the form of knowing that the bay was deep enough for me to make that kind of manoeuvres.

[SecondBase]

Originally Posted by Dockhead

This thread is not about this, but I'd just like to note a few of the errors in this post:

1. No one ever has right of way at sea. There is no such thing.

2. There is also no such thing as a burdened vessel, since the 1972 revision of the COLREGs.

3. You get in as much trouble for smashing into a vessel broadcasting Class "B" as one broadcasting Class "A" so ignore them at your peril.

3. In open water, smaller slower vessels are actually LESS maneuverable, that is, less able to change a dangerous CPA than larger faster vessels (contrary to the common misconception of small boat sailors who have never been on the bridge of a ship).

4. You don't always "give way" to commercial traffic -- in some situations and for a certain phase of certain crossings, you are obligated to hold your course and speed so that they can maneuver.

As I said, this thread is not at all about this, so if you want to start such a discussion, please start a different thread.

Dockhead,

This is an important effort you are undertaking.

One asset for the community might be a cliff notes along the lines of your listed points above. Words like "if you aren't going to put hours and days of study into the Colregs - although you should - if you aren't going to put in the study at least understand the following concepts ...

1)
2)
3)
4)

Some of your points above are well-anchored not just in Colregs but in physics as well.

I haven't read the 29 Mb paper but my thoughts on it that is that the AIS data location and speed should result in a speed-sized disk around each acquired target. Once the speed disks are around each vessel than a cone of probability is drawn for each vessel. With that out of the way it is a matter of time slice analysis for the course which best keeps you out of the cones. Along with a "no solution / alert" result possibility as well.

I believe there is a gap in recreational boaters understanding. As part of the research for your book you might do a pop quiz on at a local marina and see how the average recreational boater scores.

Should give you a good opening and maybe a chapter or two along with some additional areas for your research.

[Pelagic]

With yet another US naval ship involved in a collision in heavy traffic zones, discussion about the wisdom of using Speed versus Course Change in ML conditions should be considered.

[JPA Cate]

Pelagic: As they say here, "You're not wrong!"

Maybe Dockhead would like to copy this thread to the USN. This is getting embarrassing!

Ann

[bmz]

Originally Posted by Dockhead

When these guys talk about always giving way to ships, regardless of what the Rules say --

I have been trying to ignore this thread, but some things just need to be corrected. Colreg 18 provides that we must yield to vessels restricted in their ability to maneuver. It includes some examples of such vessels, but the rule is expressly not limited to those examples. I cited the rule of tonnage because it explains exactly why the larger a vessel is the more restricted it is in its ability to maneuver.

The National Association of State Boating Law Administrators (NASBLA), and the U.S. Coast Guard Have approved of language making it clear that large commercial vessels, by virtue of their size and/or draft, are stand on vessels. I previously cited some examples. See also, https://www.boatsmartexam.com/knowle...amid-10241.jpg

Accordingly, nothing I have said is contradicted "the Rules."

[bmz]

Originally Posted by SecondBase

Dockhead,

This is an important effort you are undertaking.

One asset for the community might be a cliff notes along the lines of your listed points above. .

No matter how hard I try to get out, they keep on pulling me back in.

Let's look at the statements that you consider to be so important that they should be "cliff notes" for the sailing community:

1. No one ever has right of way at sea. There is no such thing.
2. There is also no such thing as a burdened vessel, since the 1972 revision of the COLREGs.
3. You get in as much trouble for smashing into a vessel broadcasting Class "B" as one broadcasting Class "A" so ignore them at your peril.
3. In open water, smaller slower vessels are actually LESS maneuverable, that is, less able to change a dangerous CPA than larger faster vessels (contrary to the common misconception of small boat sailors who have never been on the bridge of a ship).
4. You don't always "give way" to commercial traffic -- in some situations and for a certain phase of certain crossings, you are obligated to hold your course and speed so that they can maneuver

Now let's address my previous unrebutted critique of your candidates for Cliff notes:

"1)You attack my use of the terms "right-of-way" and "burdened." Others on this thread used those terms for good reason--they are commonly used and everyone here fully understands them. So what's your point--to get a gold star in terminology?
2) I did not advise "ignoring" class B vessels; I said "The class B targets are all small and maneuverable, and if you are a sailing vessel most of them will have to yield to you. In any event, when you get close enough you will both see each other easily and the burden vessel should yield" More importantly you can't get into "as much trouble" crashing into a class B vessel as a class A vessel;[Crash into a class B vessel and you will scratch your fiberglass] crash into a class A vessel, and you will die."


So you think it's more important for your Cliff notes to focus on virtually irrelevant terminology distinctions as opposed to protecting the lives of sailors?

Let me also address Dockhead's allegation that small vessels are more maneuverable than large commercial vessels. I cited a number of published sources supporting my maneuverability statements; yet Dockhead's cites none supporting his. Do you have any problem with that? If not, I have a bridge, with some Cliff notes, to sell you.

Now lets address your next Cliff note: " 4. You don't always "give way" to commercial traffic -- in some situations and for a certain phase of certain crossings, you are obligated to hold your course and speed so that they can maneuver"
That is one great Cliff note you have there--"there is an exception to the rule: sometimes you don't follow it."

It really frightens me to know that you guys are out on the water; but then again, you do have your Cliff notes.

[Dockhead]

Originally Posted by bmz

I have been trying to ignore this thread, but some things just need to be corrected. Colreg 18 provides that we must yield to vessels restricted in their ability to maneuver. It includes some examples of such vessels, but the rule is expressly not limited to those examples. I cited the rule of tonnage because it explains exactly why the larger a vessel is the more restricted it is in its ability to maneuver.

The National Association of State Boating Law Administrators (NASBLA), and the U.S. Coast Guard Have approved of language making it clear that large commercial vessels, by virtue of their size and/or draft, are stand on vessels. I previously cited some examples. See also, https://www.boatsmartexam.com/knowle...amid-10241.jpg

Accordingly, nothing I have said is contradicted "the Rules."

Keep reading. This is good. The wisdom you seek is all in the Rules, in black and white, but you have to read them completely, and not just take a phrase or two out of context.

RAM (restricted in the ability to maneuver) is a very narrow and specific status, which applies only to vessels which are so restricted by the nature of their work, and furthermore this status exists only when the corresponding signals are being shown. This status applies to dredgers and the like, and does NOT indeed apply to ordinary commercial vessels.

Rule 18 is NOT indeed a catch-all provision which means that any vessel which we might guess is more maneuverable, should give way to vessels we might think are more maneuverable -- this would generate pure chaos, and the real purpose of the Rules is on the contrary to create order and predictability and make everyone know what they are supposed to do.

What vessel is "more maneuverable", and what even IS maneuverability, is not immediately obvious, in any case, and so couldn't form a predictable standard. In close quarters, of course, a smaller vessel which has a higher ROT might be. But in open water, a large commercial vessel at sea speed will have a far greater ability to change the CPA in a crossing situation with a small, slow vessel, which is one reason why professional mariners really want us to hold our course and speed when the Rules require it (there is a post in this very thread from a commercial ship captain, on that subject, if you will read through the thread).

The "Right of Way Pyramid" which you have posted about twenty times contradicts the COLREGS and in fact is fundamental nonsense. It is someone's individual teaching tool, and in no way any kind of official publication. It is wrong in so many ways that I won't even start with it, but why don't you start a thread on it if you want to know what experienced people, and professional mariners, think?

[Suijin]

Originally Posted by bmz

2) I did not advise "ignoring" class B vessels; I said "The class B targets are all small and maneuverable, and if you are a sailing vessel most of them will have to yield to you. In any event, when you get close enough you will both see each other easily and the burden vessel should yield" More importantly you can't get into "as much trouble" crashing into a class B vessel as a class A vessel;[Crash into a class B vessel and you will scratch your fiberglass] crash into a class A vessel, and you will die."

Uh...

Originally Posted by bmz

However, for the majority here whose multiple target situations occur where they are many class B targets and very few class A targets, I have a recommendation: focus on the class A target and ignore the class B targets (especially where the class A targets are large freighters who are not maneuverable, but can be quite fast).

From my perspective, this is a grossly irresponsible recommendation. It's one thing to give priority to class A targets, in certain situations, but ignoring class B targets is foolish. It can lead to far more than a "scratch in the fiberglass".

As far as Dockhead's point, he was talking about situations where there are three or more vessels, at which point there are no burdened or give way vessels; all are required to what they can to avoid a collision. Yes following COLREGS to the greatest degree possible is best practice for the sheer point of predictability, but the situation has changed.

As far as "ability to maneuver" is concerned, Dockhead is right that the "event horizon" of a large ship is much greater than that of a small boat. They are traveling at 20+ knots and thinking miles ahead. The 30' sloop traveling at 6 knots has a much shorter horizon, and much more limited ability to maneuver if they find themselves at risk of collision. Of course meeting at sea is much different than meeting in a narrow channel.

[ramblinrod]

Originally Posted by Dockhead

The conflict between time and distance horizons of WAFIs, and those of ships' bridges, seems to me to be one of the fundamental problems of collision avoidance, too little discussed. I have thought about this a great deal.

We've all had a laugh at the Joe Sixpack bow rider types and their Rule of Gross Tonnage etc., but in fact what is going on here, I am convinced, is a conflict of time/distance horizon. When these guys talk about always giving way to ships, regardless of what the Rules say -- they are actually right, within their own horizon of time/distance awareness. A mile off to them seems like a long ways, but a larger vessel is already fully committed, and we call it in extremis. Four or five cables even seems like a long ways to the bay sailor in his San Juan 24, but he often cannot even be seen already from the bridge of a large commercial vessel, nor by the radar. It would really be deadly for him to think that the ship about to run him down, four cables off, is going to change course.

I think it is extremely important to raise awareness of this issue, and teach boaters that the phase of giving way and standing on is over, long before they realize it. It's also another reason why we have to hammer into their heads to stop using the term "right of way", which is a completely different concept, also in this context.

I agree of course, and I don't think anyone has suggested going to the radio light-mindedly. It should never be necessary in a straightforward crossing involving two vessels. I've written a whole chapter on this, including extensive discussion of the MCA MGN. I completely agree with the MCA that radio comms should not be used to support sloppy non-Rules compliant maneuvering. If everyone follows the Rules in a standard crossing, then communications are not needed at all, are a waste of time, and can be crucially distracting. But a complex multi-vessel crossing is the classical case for agreeing passing arrangements, if you are unable to work out a solution on your own. Green to green passing, however, is the most common situation.

Needless to say, AIS has dramatically reduced the risks of using the VHF for passing arrangements.

Just out of curiosity, what do you believe the real and significant difference between having "right of way" and being a "stand on" vessel, or being the "burdened" or "give way" vessel, other than just terminology semantics?

I know there was a definite change in the "official" terminology many years ago, but my impression was that is was just semantics, perhaps to reduce the possible misinterpretation that a "right of way" boat had no obligation to avoid collision with a "burdened" boat, even though, to my knowledge, they always have, if the "burdened" boat, in fact, did not "give way".

[Dockhead]

Originally Posted by bmz

No matter how hard I try to get out, they keep on pulling me back in.

Let's look at the statements that you consider to be so important that they should be "cliff notes" for the sailing community:

1. No one ever has right of way at sea. There is no such thing.
2. There is also no such thing as a burdened vessel, since the 1972 revision of the COLREGs.
3. You get in as much trouble for smashing into a vessel broadcasting Class "B" as one broadcasting Class "A" so ignore them at your peril.
3. In open water, smaller slower vessels are actually LESS maneuverable, that is, less able to change a dangerous CPA than larger faster vessels (contrary to the common misconception of small boat sailors who have never been on the bridge of a ship).
4. You don't always "give way" to commercial traffic -- in some situations and for a certain phase of certain crossings, you are obligated to hold your course and speed so that they can maneuver

Now let's address my previous unrebutted critique of your candidates for Cliff notes:

"1)You attack my use of the terms "right-of-way" and "burdened." Others on this thread used those terms for good reason--they are commonly used and everyone here fully understands them. So what's your point--to get a gold star in terminology?
2) I did not advise "ignoring" class B vessels; I said "The class B targets are all small and maneuverable, and if you are a sailing vessel most of them will have to yield to you. In any event, when you get close enough you will both see each other easily and the burden vessel should yield" More importantly you can't get into "as much trouble" crashing into a class B vessel as a class A vessel;[Crash into a class B vessel and you will scratch your fiberglass] crash into a class A vessel, and you will die."


So you think it's more important for your Cliff notes to focus on virtually irrelevant terminology distinctions as opposed to protecting the lives of sailors?

Let me also address Dockhead's allegation that small vessels are more maneuverable than large commercial vessels. I cited a number of published sources supporting my maneuverability statements; yet Dockhead's cites none supporting his. Do you have any problem with that? If not, I have a bridge, with some Cliff notes, to sell you.

Now lets address your next Cliff note: " 4. You don't always "give way" to commercial traffic -- in some situations and for a certain phase of certain crossings, you are obligated to hold your course and speed so that they can maneuver"
That is one great Cliff note you have there--"there is an exception to the rule: sometimes you don't follow it."

It really frightens me to know that you guys are out on the water; but then again, you do have your Cliff notes.

This thread is on advanced topics, on one specific and narrow topic, actually. These comments are beginner level stuff, and it is a distraction. It's not to say that these questions are not interesting -- they are. But they are not for this thread. I'm starting a new one just for this discussion.

[bobgarrett]

Originally Posted by bmz

I have been trying to ignore this thread, but some things just need to be corrected. Colreg 18 provides that we must yield to vessels restricted in their ability to maneuver. It includes some examples of such vessels, but the rule is expressly not limited to those examples. I cited the rule of tonnage because it explains exactly why the larger a vessel is the more restricted it is in its ability to maneuver.

The National Association of State Boating Law Administrators (NASBLA), and the U.S. Coast Guard Have approved of language making it clear that large commercial vessels, by virtue of their size and/or draft, are stand on vessels. I previously cited some examples. See also, https://www.boatsmartexam.com/knowle...amid-10241.jpg

Accordingly, nothing I have said is contradicted "the Rules."

Notwithstanding your statement that the USCG "recognizes" this commercial organization selling a boat safety course, the USCG makes it clear that the IMO Rules are those ratified into US law.
https://www.navcen.uscg.gov/pdf/navR...B_20151231.pdf

[bmz]

I had a proofreading error in my previous post instead of "small vessels are more maneuverable" it should have read "small vessels are not more maneuverable."

[David M]

Go ahead and read the COLREG's themselves. But also purchase a book or two that interprets and clarifies the COLREG's. Reading the COLREG"S is difficult and boring as hell. The Rules themselves do not clarify what is meant by the Rules nor does it explain all the differences and little nuances.

The COLREG's just blurts out the Rules and then leaves you in the dark for everything else relating to the Rules. Besides, case histories of actual collisions and the determination of who did wrong and why are far more entertaining anyway. This is far more entertaining than darting your eyes left and right to look for any subtle difference between the Inland and International Rules. Right?

I had a total of three classes on the COLREG's before graduating from Cal Maritime. Without the additional books and the instructors adding to what I read in the COLREG's I will be the first to admit, I would not have learned nearly as much.


Examples of books that more thoroughly explain the Rules in a non-boring fashion:
https://www.amazon.com/Practical-Gui...=rules+of+road

https://www.amazon.com/Farwells-Rule...3C69CZ7JSKXG00

https://www.amazon.com/Chapman-Navig...3C69CZ7JSKXG00

[bmz]

Originally Posted by Dockhead

This thread is on advanced topics, on one specific and narrow topic, actually. These comments are beginner level stuff, and it is a distraction. It's not to say that these questions are not interesting -- they are. But they are not for this thread. I'm starting a new one just for this discussion.

I have been trying to stay out of this thread; but as I noted above, others keep bringing up the issue. I think it would be more effective if you address these comments to them

[ramblinrod]

Originally Posted by Suijin

As far as Dockhead's point, he was talking about situations where there are three or more vessels, at which point there are no burdened or give way vessels; all are required to what they can to avoid a collision.

Yes following COLREGS to the greatest degree possible is best practice for the sheer point of predictability, but the situation has changed.

This is nonsense!

Of course Col Regs covers multiple target situations.

Obligations are simply determined by considering 2 boats at a time, earliest collision first.

But one has to then consider all other possible subsequent collisions, by considering, 2 boats at a time.

If you must change course or speed to give way, only 4 things can happen.

A. All clear and no further risk of collision.

B. New collision risk, you are give way, and continue to alter course and speed in such a way that you can stand on.

C. New collision risk, your are stand on, and others alter course and speed to in such a way that they can stand on.

D. Some idiot doesn't follow the rules, and everyone has to avoid the idiot while staying clear of all other stand on vessels, still following the rules.

What am I missing?

(Of course I do not force a larger commercial freighter to change course, when from 5 miles away I can simply change course of my "stand on" little boat, by one degree, especially when course corrections to hold intended course are prolly more than that.)

To me the notion that Col Regs do not apply to multiple targets is absolutely ludicrous.