Collision Avoidance -- Dealing with Multiple Targets

[ramblinrod]

Originally Posted by Dockhead

That an obviously intelligent person like you could so totally misunderstand the basics of crossing with fast ships, is evidence that this discussion is really worth having. It might even save your life. I invited you to do the math and see for yourself; you didn't bother. I guess because you are so sure in your own concepts that you don't think you need it. Now I've done the math for you and you will see. But let's discuss it elsewhere, say here:

Collision Avoidance, Cones of Uncertainty, and Appropriate CPA - Cruisers & Sailing Forums

Sorry, collision avoidance is not that difficult if one simply keeps watch, stands on, gives way, and applies some common sense as required.

I understand that you keep selecting the worst possible scenario to sensationalize your point, but most intelligent sailors like myself don't run up the centre of south bound shipping lanes or routes heading north. I think you need to apply some reality to your argument. When one is crossing a ships course, at right angles (as they should), turning off 1 degree from 5 nm away is more than ample. If in the event one miscalculates, just luff up until you can safely pass astern. And yes, there is absolurely no reason to pass a full mile astern.

[David M]

I have gone out of my way countless times to take a ship astern so that I do not freak out the watch officer or the pilot. When one crosses ahead close (within a few minutes of the TCPA) it just makes their job miserable and makes the operator of the pleasure boat look like a total newbie.

[ramblinrod]

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.

I simply don't understand this last sentence. No where do the rules state they only apply to one of many vessels. They clearly state they apply to all vessels. The rules do not offer guidance. They specify obligations and actions to be taken.

If one is "guided" to do something different than the rules explicitly state, all hell may break loose.

How could it possibly be good, for a boater to be "guided", to do anything different or supplemental to, what colregs already clearly states.

[Pelagic]

Ramblinrod.. DH is discussing the practical strategies recommended where multiple targets can complicate normal avoidance tactics as set out in COLREGS

[Jhhastie]

This is one of the best threads I have ever read.


Sent from my iPad using Cruisers Sailing Forum

[ramblinrod]

Originally Posted by Pelagic

Ramblinrod.. DH is discussing the practical strategies recommended where multiple targets can complicate normal avoidance tactics as set out in COLREGS

Oh OK,

Here is my strategy.

Always Follow Colregs.

When multiple vessels are involved that you are the give way vessel to, plot a course to deal with the most imminent risk of collision first, while maintaining your stand on obligation where required, and dealing with each subsequent risk in turn.

When a course is determined where all obligations are satisfied, execute.

Should conditions change, re-evaluate.

If no solution is possible, still following Colregs, sound 5 quick blasts and stop.

When a solution becomes available, proceed.

[Pelagic]

What you describe is multilateral considerations and is assuming that all the other vessels cooperate with you and each other.

If confused......Stopping and sounding the Danger signal may not be advisable in confined areas of many converging channels and strong currents such as the Seto Naikai where 15 ships are surrounding you from different Aspects

That is part of Rule 2 guidance

[Snore]

My charter guests is going to be 90 min late, so I catch up on a this thread.

IMHO the premise of the thread is flawed. Let's assume the worst-- you are crossing the entry to a major port and somehow it does not have a TSS. The crossing of each vessel you encounter would be governed by ColRegs. For you to encounter 2 vessels in such a tight time line the you could not maneuver a 55-70' vessel to comply assumes the two targets would collide.

For example my vessel is headed 345, target 1 is headed 270 (crossing not overtaking) and target 2 is headed 045. Assuming all would collide without action, target 2 is giveaway to all and I am giveaway to target 1. If I was clear of target 2 but his avoidance of target 3 made me an issue, I cannot see a crossing that would make target 2 stand-on.

Even if I was in some manner giveaway to target 2, his failure or inability to properly stand-on would make him give way and could result in a radio call. "Vessel X this Target 2, Please stand on I'm gonna have to take your stern." Assuming I had situational awareness, I would see this unfolding.

Can someone provide an example where you could not address each crossing as a separate event such that a simple yield of equal vessels would not work (no CBD or restricted, etc)?

[ramblinrod]

Originally Posted by Pelagic

What you describe is multilateral considerations and is assuming that all the other vessels cooperate with you and each other.

If confused......Stopping and sounding the Danger signal may not be advisable in confined areas of many converging channels and strong currents such as the Seto Naikai where 15 ships are surrounding you from different Aspects

That is part of Rule 2 guidance

Incorrect. If there is no solution to avoid collision it is your last and only option.

[ramblinrod]

Originally Posted by Snore

My charter guests is going to be 90 min late, so I catch up on a this thread.

IMHO the premise of the thread is flawed. Let's assume the worst-- you are crossing the entry to a major port and somehow it does not have a TSS. The crossing of each vessel you encounter would be governed by ColRegs. For you to encounter 2 vessels in such a tight time line the you could not maneuver a 55-70' vessel to comply assumes the two targets would collide.

For example my vessel is headed 345, target 1 is headed 270 (crossing not overtaking) and target 2 is headed 045. Assuming all would collide without action, target 2 is giveaway to all and I am giveaway to target 1. If I was clear of target 2 but his avoidance of target 3 made me an issue, I cannot see a crossing that would make target 2 stand-on.

Even if I was in some manner giveaway to target 2, his failure or inability to properly stand-on would make him give way and could result in a radio call. "Vessel X this Target 2, Please stand on I'm gonna have to take your stern." Assuming I had situational awareness, I would see this unfolding.

Can someone provide an example where you could not address each crossing as a separate event such that a simple yield of equal vessels would not work (no CBD or restricted, etc)?

Well let's not open that can of worms, er, um, actually lets. Think of a can of worms. None can turn or advance without risk of contact with another. The only solution is for all to stop. I agree stopping is not the solution if another maneuver will meet all Colregs obligations, but if another maneuver is not possible without violating Colregs, stopping is the final and only maneuver (unless your Captain Kirk.) ;-).

It would be highly unlikely this could ever happen, but would be akin to gridlock in a city. Nobody can move until the outside boundary vehicles clear out of the way.

[Pelagic]

Originally Posted by ramblinrod

Incorrect. If there is no solution to avoid collision it is your last and only option.

Another solution could also be to slowly turn away from the congestion , even back onto a reciprocal heading until the traffic clears so that you can return to your course.
This allows you to maintain control in strong currents and take further avoiding actions if necessary.

What we are discussing here are extreme conditions so i agree that stopping to wait out the congestion is a valid tactic

But not the only one!
....keep in mind that a vessel underway but not making way, still has an obligation to avoid a collision under the rules

[Dockhead]

Originally Posted by ramblinrod

Sorry, collision avoidance is not that difficult if one simply keeps watch, stands on, gives way, and applies some common sense as required.

I understand that you keep selecting the worst possible scenario to sensationalize your point, but most intelligent sailors like myself don't run up the centre of south bound shipping lanes or routes heading north. I think you need to apply some reality to your argument. When one is crossing a ships course, at right angles (as they should), turning off 1 degree from 5 nm away is more than ample. If in the event one miscalculates, just luff up until you can safely pass astern. And yes, there is absolurely no reason to pass a full mile astern.

Sure, it's "not that difficult" -- until it is. Most encounters with ships are not head-on, but sometimes you can't avoid them. If you are set up to pass behind a ship and find yourself still too close (but still passing behind), then yes, you can luff up (or heave to, or tack) and improve the situation.

But if you sail in busy waters (and I'm not talking about bays and harbors), sooner or later you will get into a situation which is not one of these easy ones. Not that rarely you have to pass through a line of ships and you will inevitably be passing ahead of a ship as well as behind. Sometimes you meet ships head-on. Sometimes you get into a situation with multiple ships coming at your from different directions. And then you really need more knowledge and skill.

Some sailors are interested in acquiring it; others are not interested, don't care, or don't believe you ever need to know anything anyway. I'm a member of the first group.


One very small quibble with your post -- one degree is never enough to turn a possibly dangerous crossing into a safe one, even in a perpendicular crossing. Remember you can't be safe by avoiding the "exact same place" where the ship will be at CPA -- because you can't know that. You have to avoid the whole area where he might be, and where you might be, considering what you don't know about his course-keeping, exact location, etc. One degree is not even within the margin of error of your own course-keeping, not to speak of variations of your speed, and much less the various uncertainties of his position. Make all your course changes for collision avoidance large and obvious -- as the Rules require, and keep a safe distance away from ships. Sure, a mile is not essential when passing behind, you're right, but make it least a few cables.

[Dockhead]

Originally Posted by ramblinrod

I simply don't understand this last sentence. No where do the rules state they only apply to one of many vessels. They clearly state they apply to all vessels. The rules do not offer guidance. They specify obligations and actions to be taken.

If one is "guided" to do something different than the rules explicitly state, all hell may break loose.

How could it possibly be good, for a boater to be "guided", to do anything different or supplemental to, what colregs already clearly states.

You and I are in total agreement, that the Rules should always be respected and followed, and also, that almost everything you need to know about collision avoidance, is contained within them.

But that doesn't mean that there are not some nuances which require interpretation, or situations where there isn't quite enough in the Rules to know everything. Multiple targets is one of those situations -- not specifically mentioned and with no particular guidance beyond the rules for more simple crossings. Of course, most multiple target situations can be dealt with as you suggest -- take them one at a time, and follow the Rules in every case. That's the same thing I do! But sometimes the only way around one target brings you into a collision course with another one. Not even all that rarely.

And "just stopping" isn't always a good solution, either -- if you're in a busy traffic area, that can leave you as a sitting duck, without any ability to maneuver.

This thread so far confirms what I suspected -- that there isn't any silver bullet and that we just have to muddle through somehow, calling to make passing arrangements if necessary.

[Dockhead]

Originally Posted by Pelagic

Another solution could also be to slowly turn away from the congestion , even back onto a reciprocal heading until the traffic clears so that you can return to your course.
This allows you to maintain control in strong currents and take further avoiding actions if necessary.

What we are discussing here are extreme conditions so i agree that stopping to wait out the congestion is a valid tactic

But not the only one!
....keep in mind that a vessel underway but not making way, still has an obligation to avoid a collision under the rules

Stopping can be a great move if you have a place to stop which is out of traffic. I do it often -- usually by heaving to. Or by making a 180 back onto a reciprocal course (probably better in most cases, for the reasons you mention).

But stopping is not a solution at all if there is other traffic bearing down on you. Stopping can be doubly dangerous since having no way on means you can't maneuver. As you correctly state, stopping does not relieve you of the obligation to maneuver to avoid a collision -- even if you are the stand-on vessel!! -- but deprives you of the ability to do so, so use this tactic with caution!!

[roland stockham]

One thing I have not seen much mention of so far is AIS. Personally I have found it one of the most useful developments of the last few decades and would put it on a par with GPS as a safety aid. Yes like GPS there are issues with it and over reliance is one of them! In the same way that you get problems if people rely only on GPS and don't use radar, mark 1 eyeball and common sense you have problems. With AIS if you spend all your time looking at it and get into a 'virtual navigator' mode or assume that it make you visible to every one then you have a problem.
That said I think it contributes a few very important things to the mix in these complex situations. We can assume now that all large ships have AIS fitted and can confirm that by observing their signal (which is not the same as them looking at it!). If you have a transponder you also give them the same advantage. The big difference is that it also give an estimate of CPA which is faster and often I find more accurate than plotting with a compass. This allows better planning in complex situations. However I find the most useful information is that it shows rate of turn. Quite often it is hard to judge whether large ships are changing course by visual observation, you need to wait for their aspect to change. AIS tells you immediately that a target is responding to the situation by, say turning to starboard. I confirms they are taking action. I have been amazed to watch ships alter course by adegree or two at 10 miles out to adjust passing distances while they are still a dot on the horizon to me. Like GPS it takes a while to learn to get the best from AIS and maybe this is an area where we could develop some guidance for small boat sailors, whether new to sailing or new to AIS. I can thing of a few poor vis nights in the English Channel when I would have offered up my first born for such tech but then that was before we even had GPS but then again many people used to sail more cautiously, but that's another thread!!!