Collision Avoidance -- Dealing with Multiple Targets

[Corsair 2]

I agree with David M. Don't be shy to use the radio. Here is a real life AIS collision situation in which I was the privileged vessel --- but the cargo vessel had not (yet) altered course, so I gave him a courtesy call on the radio (also in the video). I film the cargo vessel's reply and change of course. (The collision avoidance sequence starts at about 7 minutes.)

https://youtu.be/pSke1xN0kq8

Regards
Patrick

[captmikem]

I agree with David M. Every 5 years I have to take a test to renew my radar license. You are given 10 plots with multiple targets and have to figure it all out.. It is pretty easy if you do it regularly, or if you pick up a test prep book.

The prep book might be handy for you DockHead, I think I have one on PDF if you need it.

Also, one of the things people tend to forget is that they can SLOW DOWN to avoid a situation. And turning to port is not an option 99.999 % of the time.

(now I have to admit here, if I am in a small boat and my radar shows a ship crossing my port bow and not altering with a cpa of less than a mile and I am 5 or more miles away from a ship I will give her a bit to port so that I will clear his stern. Ships work in 6 minute intervals (one tenth of an hour) so if he has not altered at 6 he probably is not going to alter. My assumption being that he has not seen me.) If it were a small boat like me I would hold my course.

Make your alterations early and enough of a course change that it is obvious to the stand on vessel. At least 30 degrees.

M

[wjhutchings]

The Collision Regulations

They are simple and easy to use as long as everybody uses them, unfortunately not everyone knows them and not all those that do use them properly.

The adage steam gives way to sail still holds good, though this is tempered by the requirements of rules 9 & 10 in that a sailing vessel or a power driven vessel of less than 20 metres in length must not impede the progress of a power driven vessel that can only safely navigate in a narrow channel or traffic separation scheme in some countries such as NZ it is an offence for such vessel to impede the progress of a vessel under pilotage whether there is room for the larger vessel to give way.

I am a professional mariner with more years sailing around the waters of the world than I care to remember, I believe that your eyes give you far more appreciation of the situation around you than either radar or AIS, and the one thing I flatly refuse to do is get engaged in conversations on the radio with other vessels I have seen so much confusion after radio conversations even after identification mainly language based that it is more trouble than it is worth.

For the originator of the this conversation all I can say is unless you are in poor visibility, always run a plot but remember your brain can only process about 5 - 10 well even if the machine can plot 20 so discard those that are of no concern I.e. passing outside of the CPA which you believe is the nearest you would wish a vessel to approach say 1 or 2 miles, visually identify the targets which you are interested in and use both your eyes and your electronics to ensure a safe passage.

One thing a small vessel owners must remember is that GRP & wooden vessels even with a radar reflector do not reflect a good radar signal and your signal will be lost in the sea clutter, especially if it is breezy or suppressed completely if the radar operator has the auto clutter suppression on . the other thing is that when fitted with AIS though all the vessels around you will receive your signal, the person receiving it has to process this and in very busy waters such as the English Channel, Malacca and Singapore Strait etc., there is such a thing as information over load so targets can be missed so that is why visually identifying individual targets is so important.

I suggest to small vessel owners who find themselves at sea in low visibility treat everything as a threat and keep out of their way, may mean a longer journey but most probably a safer one

[Corsair 2]

Well, I'd agree with you WJH that talking on the radio should not be necessary. However, if I am the stand-on vessel and the other boat/ship is not maneuvering, I make a quick radio call (like the one in the short video I posted above). I have never had a problem doing this: short, clear comms where I state my intentions, e.g., 'maintaining course and speed', or 'turning to starboard', etc.

Wondering in silence if the burdened vessel is going to maneuver as we get closer and closer is a bit too stressful for me.
Best regards

[The Way]

Originally Posted by David M

If 16 and 13 are jammed then still stick to the COLREGS, always.

This reminds me of a question I've had often in crowded harbors -- some vessels are monitoring 16, others 13. What do I do, try to hail on each one? But while waiting for an answer on the wrong channel, time is getting shorter.

Thanks for any advice,
Jack

[KiwiKen]

Originally Posted by Dockhead

This is correct of course, and this thread is not really to discuss that.

I'm interested in specific tactics for multiple targets - the Rules don't give us a lot of guidance.

Step 1 assess which vessel is the stand on vessel and give way vessel in relation with each target starting with the closest.

Step 2 Manoeuvre your vessel in relation to each potential collision close quarters situation in sequence, but be mindful that you should not make a change of course in relation to one close quarters situation that creates another potential collision situation.

One should be mindful of Rule 8:
(b) that any alteration of course or speed should be timely and of sufficient magnitude to be obvious to other vessels.
(e) that slowing, stopping or reversing, is an option.
Stopping is frequently an excellent option in such situations.

Certainly contacting close by vessels and agreeing a course of action in relation to the situation between the two of you is sound advice, but can be tricky where multiple vessels are included.

What is important is that whoever is on watch on other vessels is not put in the position of having to try guess what another vessel is doing or might do.

With relation to the Channel separation zones, a yacht should only cross these zones as near as possible to right angles, and has no business traveling in the direction of the lane.

I can recall on one occasion counting 65 vessels I could see above our visual horizon in the Dover straights, it can be quite busy, and this traffic density can be 24 x7 irrespective of weather and visibility.

[Pelagic]

Originally Posted by Dockhead

I'm working on a guide to collision avoidance, and one of the subjects is dealing with multiple targets.

A crossing in open water with a single vessel cannot be that complicated. There will be one way to turn which will increase the CPA. Do it at the right time, and all is good.

But as we all know, sometimes you don't have complete freedom. One of those situations is when the one turn which increases CPA is an awkward one -- one which creates a green to green pass, for example, or one which requires a turn to port from an angle which is risky in case the other vessel turns to starboard. Another situation is when you are dealing with multiple targets at once.

Anyone have any good technique or insight to share? I can't say that I do anything especially ingenious myself. I try to figure out whether there is one turn which increases CPA to all targets at once (even if it's a 180). If not, then I try to figure out whether there is some turn which will create an acceptable CPA with all targets (which can be complex to figure out, but using OpenCPN and displaying the different position at CPA makes it a lot easier). OR, if TCPA is much different, then you can turn one way with respect to the closer target, then turn again.

It's much more complicated if you are stand-on with respect to any of the targets -- makes you wish you weren't. I have a guilty confession to make -- one time in the North Sea passing through a gaggle of ships going in different directions, I falsely raised a motoring cone, to give myself freedom of maneuver, when I was not actually entitled to it.

Dealing with multiple targets at once is also the classic case for needing to use the radio. To explain to one vessel that you will be doing such and such, because you've got another vessel somewhere you have to stay clear of, or to request some action by the stand-on vessel to help resolve such a situation, or to request a give-way vessel to hold course and speed.

Anyone have anything to add to this?

Hi Dockhead
In Marine Colledge and during Simulator exams they call it "Multilateral Considerations" .(MC)

Assesment first including running Test Maneuvers on your ARPA radar to find a solution, if you have that feature.

Because MC's are so dynamic often causing a chain reaction of course changes and getting into navigational limits, switching to True Radar presentation, ground stabilized is helpful to immediately detect course changes.

Sometimes for a yacht the best advice when you detect a bottleneck of conflicting ship traffic ahead of you is to stop or make a complete U-Turn to allow the big boys to sort it out, before resuming course.

Lastly, communicating your intentions to the group of traffic before execution will help them with their own avoidance plan

[ramblinrod]

Originally Posted by Dockhead

I'm working on a guide to collision avoidance, and one of the subjects is dealing with multiple targets.

A crossing in open water with a single vessel cannot be that complicated. There will be one way to turn which will increase the CPA. Do it at the right time, and all is good.

But as we all know, sometimes you don't have complete freedom. One of those situations is when the one turn which increases CPA is an awkward one -- one which creates a green to green pass, for example, or one which requires a turn to port from an angle which is risky in case the other vessel turns to starboard. Another situation is when you are dealing with multiple targets at once.

Anyone have any good technique or insight to share? I can't say that I do anything especially ingenious myself. I try to figure out whether there is one turn which increases CPA to all targets at once (even if it's a 180). If not, then I try to figure out whether there is some turn which will create an acceptable CPA with all targets (which can be complex to figure out, but using OpenCPN and displaying the different position at CPA makes it a lot easier). OR, if TCPA is much different, then you can turn one way with respect to the closer target, then turn again.

It's much more complicated if you are stand-on with respect to any of the targets -- makes you wish you weren't. I have a guilty confession to make -- one time in the North Sea passing through a gaggle of ships going in different directions, I falsely raised a motoring cone, to give myself freedom of maneuver, when I was not actually entitled to it.

Dealing with multiple targets at once is also the classic case for needing to use the radio. To explain to one vessel that you will be doing such and such, because you've got another vessel somewhere you have to stay clear of, or to request some action by the stand-on vessel to help resolve such a situation, or to request a give-way vessel to hold course and speed.

Anyone have anything to add to this?

What you are looking for is Col Regs. If everyone follows them, nothing bad will happen. Don't try to invent something that deviates or your #%{%}% could be in a sling. They are tried, true, and proven.

[hiebert]

Originally Posted by Dockhead

No, that's not quite correct. The steering and sailing rules continue to apply -- with respect to each crossing vessel individually. But Rule 2 allows you to deviate somewhat according to the necessities of the situation. And you apply Rule 2 to govern your actions when the other rules don't tell you what to do.

The International COLREGS applies even when you are dealing with more than 1 vessel. Rule 2 will only apply when you find yourself in a situation where if you followed the Head-on, Crossing, or Overtaking rule you will get into a collision. That situation would arise when the other vessel/s are not complying with the rules, but you are trying to follow the rule and if you follow the rule you will collide. The best thing to do is to take early action, substantial action so it is obvious to the other vessel and keep well clear. The problem with our current International COLREGS is it is a little vague, it does not tell you what is early or what is substantial. It is left to the boater/mariner. If there is a collision, then the authorities will tell you that it was NOT early or NOT substantial. A rule of thumb would be to take action about 15 minutes to TCPA and any course alteration is more than 15 degrees.

[ramblinrod]

Originally Posted by Dockhead

I'm working on a guide to collision avoidance, and one of the subjects is dealing with multiple targets.

A crossing in open water with a single vessel cannot be that complicated. There will be one way to turn which will increase the CPA. Do it at the right time, and all is good.

But as we all know, sometimes you don't have complete freedom. One of those situations is when the one turn which increases CPA is an awkward one -- one which creates a green to green pass, for example, or one which requires a turn to port from an angle which is risky in case the other vessel turns to starboard. Another situation is when you are dealing with multiple targets at once.

Anyone have any good technique or insight to share? I can't say that I do anything especially ingenious myself. I try to figure out whether there is one turn which increases CPA to all targets at once (even if it's a 180). If not, then I try to figure out whether there is some turn which will create an acceptable CPA with all targets (which can be complex to figure out, but using OpenCPN and displaying the different position at CPA makes it a lot easier). OR, if TCPA is much different, then you can turn one way with respect to the closer target, then turn again.

It's much more complicated if you are stand-on with respect to any of the targets -- makes you wish you weren't. I have a guilty confession to make -- one time in the North Sea passing through a gaggle of ships going in different directions, I falsely raised a motoring cone, to give myself freedom of maneuver, when I was not actually entitled to it.

Dealing with multiple targets at once is also the classic case for needing to use the radio. To explain to one vessel that you will be doing such and such, because you've got another vessel somewhere you have to stay clear of, or to request some action by the stand-on vessel to help resolve such a situation, or to request a give-way vessel to hold course and speed.

Anyone have anything to add to this?

What you are looking for is Col Regs. If everyone follows them, nothing bad will happen. Don't try to invent something that deviates or your #%{%}% could be in a sling. They are tried, true, and proven.

Our first year sailing, we sailed into a narrowing harbour (from 1/2 mm to 100 feet wide) while the local yacht club had their sailpast, coming out. They were beating, we were broad reaching. It was quite the ballet, with lots of course changes to give way where Regs required. Everyone did exactly as they should and there wasn't any question about who needed to do what.

Anyone who races has learned how deal with stand on / give way in close quarters.

[ramblinrod]

Originally Posted by ramblinrod

What you are looking for is Col Regs. If everyone follows them, nothing bad will happen. Don't try to invent something that deviates or your #%{%}% could be in a sling. They are tried, true, and proven.

Our first year sailing, we sailed into a narrowing harbour (from 1/2 mm to 100 feet wide) while the local yacht club had their sailpast, coming out. They were beating, we were broad reaching. It was quite the ballet, with lots of course changes to give way where Regs required. Everyone did exactly as they should and there wasn't any question about who needed to do what.

Anyone who races has learned how deal with stand on / give way in close quarters.

I should add that the sailpast was 20 years ago and I remember it like yesterday it was such a beautiful thing.

[Jim Cate]

Originally Posted by ramblinrod

I should add that the sailpast was 20 years ago and I remember it like yesterday it was such a beautiful thing.

A nice memory, Rod, but has little relationship with what DH is considering: interactions with multiple large, fast vessels at sea, perhaps in poor visibility and in harsh weather.

Jim

[Dockhead]

Originally Posted by ramblinrod

What you are looking for is Col Regs. If everyone follows them, nothing bad will happen. Don't try to invent something that deviates or your #%{%}% could be in a sling. They are tried, true, and proven.

You're preaching to the choir! Of course. You don't even have a choice in the matter -- the Rules are the law - they are not optional.

[Dockhead]

Originally Posted by Pelagic

.. .

Sometimes for a yacht the best advice when you detect a bottleneck of conflicting ship traffic ahead of you is to stop or make a complete U-Turn to allow the big boys to sort it out, before resuming course.

.. .

I agree completely.

An important part of collision avoidance is what you can do before a risk of collision ever arises. The 180 turn (referred to on the very first post in this thread) and removing yourself from a developing situation is an important tactic, very often the right thing to do, when you can do it early enough..

[Pelagic]

Yes another trick in high density crossing traffic for a sailboat is to get up behind a larger target that matches your speed (sometimes an offshore tug and barge) and follow behind them.

In those dense conditions (especially at night) I am motorsailing and not showing sailing lights as I don't want to create confusion as to my intentions and prefer to demonstrate my intended Rhumb Line to a destination.