Crossing Shipping Lanes (again)

[Yealm]

Aah - so is there anything in Colregs that advises for or against turning to port or starboard if you’re the give way vessel? (I don’t mean turning and crossing in front of another another vessel, I mean turning to become parallel with.

"RULE 17 Action by Stand-on Vessel"

Just to try and clarify an important point RULE 17 Action by Stand-on Vessel. as the title implies does not restrict the options available to the give way vessel. It imposes certain burdens or requirements on only the stand on vessel.
Rule 17 is worthy of an entire thread or even a book certainly lots of case law exists.

JM already gave a very simple explanation of why rule 17 imposes a restriction on the stand on vessel altering to port.
The give way vessel may still take action as is required . This action will very likely be an alteration to starboard.

An alteration to Port by a stand on vessel may appear to be a simple resolve but could in practice be very dangerous.

A small point to remember. "Not all stand on vessels have the give way vessel on their port side". When "sailing" the power driven give way vessel may be on your starboard side.

In Practice rule 17 advises don't alter towards a give way vessel. This would be a situation where an alteration to port would be safer.

 

[dom]

I'll give you an example;
Crossing Biscay last year and running in roughly NE toward Benodet about 80 miles off, motor sailing. AIS showed two ships at roughly 90 to my track, presumably going to/from Bilbao/Santander, one a smallish bulk carrier the other a cruise ship / ferry. I'm clearly give way to the bulk carrier and stand on the ferry. AIS shows that we'll all meet within about a mile circle, in particular the ferry is consistently showing a CPA of 0 to 500 metres crossing ahead at 5 miles out. Ferry cant go to port as he conflicts with the bulk and shows no sign of making a turn to starboard in about 30 mins of monitoring which he needed to do to give me the security of a clear and unambiguous turn to indicate intention to pass astern.

To my mind the ferry was not following IRPCS as he was not making his intentions clear within my comfort zone - I appreciate thats my comfort zone. In general OpenCPN is pretty good at plotting CPAs and crossing points, especially as I have both my track and target tracks set up to show 30 mins of travel - in short I've learned to trust it. I dont transmit AIS but do have a radar transponder which was on. This sort of situation is more typical in my experience than the turns others report. I wont tell what I did because not really relevant to my point but you can probably guess

Edit: Actually, because its relevant, what I did was make a 60-70 turn to port until I was clear to go behind both ferry and bulk. That, IMO, was clear and unambiguous to the ferry about my intention. The ferry didnt alter

These 3-way encounters like that do have the makings of a Mexican standoff !!

Real-life sits are however always interesting, but a few more facts wld be helpful here. Monitoring 30m ahead, while commendable, will have alerted you when the other two vessels were some 15m apart (assuming ferry @ 18kts and coaster @ 12kts). Decision time wld prob have been c.6-8m from CPA, which with at a closing spd of 30kts wld have been 12-15mins away for the other two.

Not saying you did anything wrong here, but not sure the ferry did either. As a matter of interest, how far out were you when you actioned your turn to port?.

Also, do you you or anyone else know how the OpenCPN CPA/TCPA algo works, as probabilistic 'danger zones' and CPA risk levels can be really tricky?

 

[RobbieW]

...
Real-life sits are however always interesting, but a few more facts wld be helpful here. Monitoring 30m ahead, while commendable, will have alerted you when the other two vessels were some 15m apart (assuming ferry @ 18kts and coaster @ 12kts). Decision time wld prob have been c.6-8m from CPA, which with at a closing spd of 30kts wld have been 12-15mins away for the other two.

Not saying you did anything wrong here, but not sure the ferry did either. As a matter of interest, how far out were you when you actioned your turn to port?.
...

Having looked at OpenCPN, I still have the 3 hourly plots I tend to use on a long passage on the chart. So the crossing angles were more like 60/120 with the bulk coming from behind at 60 and the ferry from ahead at 120. I also looked at my settings and I've misstated a little, its the COG predictor for both own vessel and target that I have set for 30mins. My 'warnings' are set for vessels with a CPA/TCPA of 1Nm and 30 mins respectively.

iirc I initiated the turn at about 5-6 miles from the ferry and 2 miles or so from the intercept point. I'd been monitoring both ships for about 30 mins prior to that and its from that monitoring that I saw no change in the COG or CPA of the ferry. This was around 0700 and with good visibility, turning to starboard would have taken me a long way out of my way (having reminded myself by looking at the chart) so chose to alter to port and minimise my course change whilst watching the ferry for any indication of change.

...Also, do you you or anyone else know how the OpenCPN CPA/TCPA algo works, as probabilistic 'danger zones' and CPA risk levels can be really tricky?

I interpret that question rather differently to the way I think your asking it So, I have no idea how the code works but the way the results are displayed make the situation very clear. The OpenCPN doc pages give some good illustrations and cover the set up options fully, https://opencpn.org/wiki/dokuwiki/doku.php?id=opencpn:opencpn_user_manual:toolbar_buttons:ais. GHA may also be along with some screen captures as I think he's posted those before. I dont know what the latest plotters do for AIS CPA/TCPA but OpenCPN had been way ahead of the field for a number of years in this area. Looking at the doc illustration, the dashed line between COG predictors shows the CPA; when the blue dots overlap your gonna be close so hovering the pointer over the target shows the CPA/TCPA as well as MMSI and name - at least thats the way I have it set up.

 

[Uricanejack]

Aah - so is there anything in Colregs that advises for or against turning to port or starboard if you’re the give way vessel? (I don’t mean turning and crossing in front of another another vessel, I mean turning to become parallel with.

To put it very simply. No.

The next obvious question. Why is an alteration to starboard the recommended practice. If the rules do not give specific direction to alter to starboard.

Which unfortunately is not a short simple answer.

The rules do not apply in isolation. In any given situation rules 1 to 10 apply to all vessels. 11 through 18 to vessels in sight of one and other and when vessels are not in sight of one and other rule 19 applies.

RULE 15 Crossing Situation When two power-driven vessels are crossing so as to involve risk of collision, the vessel which has the other on her own star- board side shall keep out of the way and shall, if the circum- stances of the case admit, avoid crossing ahead of the other vessel.

Although no direction is given to alter to starboard. Direction is given to keep clear and avoid crossing ahead.

RULE 16 Action by Give-way Vessel Every vessel which is directed to keep out of the way of another vessel shall, so far as possible, take early and substantial action to keep well clear.

As you can see rule 16 requires the give way vessel to take early and substantial action to keep well clear.
So back to rule 15. The PDV with the other PDV on her starboard side is required to take early and substantial action to keep well clear and if the circumstances admit avoid crossing ahead of the other vessel.

RULE 2 Re sp o n s i b i 1 i ty (a) Nothing in these Rules shall exonerate any vessel, or the owner, master or crew thereof, from the consequences of any neglect to comply with these Rules or of the neglect of any precaution which may be required by the ordinary practice of seamen, or by the special circumstances of the case. (b) In construing and complying with these Rules due regard shall be had to all dangers of navigation and collision and to any special circumstances, including the limitations of the vessels involved, which may make a departure from these Rules necessary to avoid immediate danger

Rule 2 always applies. Rule 2 requires the practice of good seamen. or common sense. All the time. Usually you will see rule 2 quoted when the situation is one in which common sense requires a departure from the rules. Obviously where there is no special circumstance rule 2 requires the rules to be followed.

To complicate it further. Rule 17

(c) A power-driven vessel which takes action in a crossing situa- tion in accordance with sub-paragraph (a)@) of this Rule to avoid collision with another power-driven vessel shall, if the circumstances of the case admit, not alter course to port for a vessel on her own port side.

Rule 17 C by giving direction to the stand on vessel not to alter course to port for a vessel on her own port side. This implies a give way vessel will alter course to starboard.

The implication is both vessels by altering to starboard will not alter towards each other. The will alter away from each other.

back to rule 2

So back to rule 15. The PDV with the other PDV on her starboard side is required to take early and substantial action to keep well clear and if the circumstances admit avoid crossing ahead of the other vessel. Add the requirements of rule 2. Apply the practice of good seamen. Without a special circumstance requires The give way vessel to take . The simple best action to keep well clear and avoid crossing ahead is an early and readily apparent alteration of course to starboard to pass astern of the stand on vessel.

Simple really an alteration of course to starboard to pass astern is just plain old common sense unless there is some kind of special circumstance.

Clear as Mudd?

 

[{151760}]

I'll give you an example;
Crossing Biscay last year and running in roughly NE toward Benodet about 80 miles off, motor sailing. AIS showed two ships at roughly 90 to my track, presumably going to/from Bilbao/Santander, one a smallish bulk carrier the other a cruise ship / ferry. I'm clearly give way to the bulk carrier and stand on the ferry. AIS shows that we'll all meet within about a mile circle, in particular the ferry is consistently showing a CPA of 0 to 500 metres crossing ahead at 5 miles out. Ferry cant go to port as he conflicts with the bulk and shows no sign of making a turn to starboard in about 30 mins of monitoring which he needed to do to give me the security of a clear and unambiguous turn to indicate intention to pass astern.

To my mind the ferry was not following IRPCS as he was not making his intentions clear within my comfort zone - I appreciate thats my comfort zone. In general OpenCPN is pretty good at plotting CPAs and crossing points, especially as I have both my track and target tracks set up to show 30 mins of travel - in short I've learned to trust it. I dont transmit AIS but do have a radar transponder which was on. This sort of situation is more typical in my experience than the turns others report. I wont tell what I did because not really relevant to my point but you can probably guess

Edit: Actually, because its relevant, what I did was make a 60-70 turn to port until I was clear to go behind both ferry and bulk. That, IMO, was clear and unambiguous to the ferry about my intention. The ferry didnt alter

There's absolutely nothing wrong with what you did. You altered course early to avoid a potential collision situation, as advised by the ColRegs. The "don't turn to port" thing applies to collision avoidance situations, i.e. close quarters manoeuvring. If you had stood on with a CPA of only 500metres, that would have been a collision risk situation.

 

[dom]

Having looked at OpenCPN, I still have the 3 hourly plots I tend to use on a long passage on the chart. So the crossing angles were more like 60/120 with the bulk coming from behind at 60 and the ferry from ahead at 120. I also looked at my settings and I've misstated a little, its the COG predictor for both own vessel and target that I have set for 30mins. My 'warnings' are set for vessels with a CPA/TCPA of 1Nm and 30 mins respectively.

iirc I initiated the turn at about 5-6 miles from the ferry and 2 miles or so from the intercept point. I'd been monitoring both ships for about 30 mins prior to that and its from that monitoring that I saw no change in the COG or CPA of the ferry. This was around 0700 and with good visibility, turning to starboard would have taken me a long way out of my way (having reminded myself by looking at the chart) so chose to alter to port and minimise my course change whilst watching the ferry for any indication of change.



I interpret that question rather differently to the way I think your asking it So, I have no idea how the code works but the way the results are displayed make the situation very clear. The OpenCPN doc pages give some good illustrations and cover the set up options fully, https://opencpn.org/wiki/dokuwiki/doku.php?id=opencpn:opencpn_user_manual:toolbar_buttons:ais. GHA may also be along with some screen captures as I think he's posted those before. I dont know what the latest plotters do for AIS CPA/TCPA but OpenCPN had been way ahead of the field for a number of years in this area. Looking at the doc illustration, the dashed line between COG predictors shows the CPA; when the blue dots overlap your gonna be close so hovering the pointer over the target shows the CPA/TCPA as well as MMSI and name - at least thats the way I have it set up.

Yikes, so the coaster was also a give-way vessel !

Edit: prob wld have done the same as you myself. To be fair to the ferry though, you altered 6m from him so I'm guessing he was even farther than that from the coaster - a tad early for a firm course alteration?

Re the OpenCPN: seems like good stuff, but as you suggest the devil's in the coding of those pink boxes. The idea is simple enough: each vessel has a speed and a heading and the pink box is something like a 2-sigma (std dev) area - you'd have to ask the coders I guess. But how does one work that up? One approach is to assign a std variance parameter for to vessels. Another is to assign one by vessel designation (ship, fishing vessel, yot, mobo, etc.). Then one can of course modify either of these for the stability of the AIS tracks in question.

One way wld be for the software to ask "Do you feel lucky?" Well, do ya, punk?" and let the user set his own probability threshold, but that wld of course be unfair on other vessels!

Sounds like you're a safe navigator BTW

 

[RobbieW]

Yikes, so the coaster was also a give-way vessel !

Yesish but he was going to pass comfortably ahead anyway without me doing anything, it was the ferry that complicated things

 

[Mariner69]

The 'Round Turn' often allows time for matters to sort themselves out. For example where the give way vessel fails to alter, then turning to starboard and following around to starboard (very carefully watching the other vessel to see what new entertainment he is devising) allows sea room and time for you to think. Works well in +200 metre length bulk carriers and 150 metre warships down to 25 feet of ocean splendour.

I also note that at least one contributor seems to believe that you must hoist a black cone (at page 6) to show that a sailing yacht is under motor. The cone is only required when operating the machinery with the sails up; to show you are not constrained in your manoeuvring. The fact that you have lowered your sails would suggest you are relying on some alternative means of propulsion.

As a watch keeper all I every wanted of yachts was that they followed the Rules. If they did that then I would be able to apply the rules from my large, faster position miles away from them and have no worries. Where a clown sails across the bows of a large vessel in confined waters and then turns around to tack right back in front they are likely to incur some approbation from the large vessel. Given the choice between running down a small yacht that has just done that manoeuvre or putting a large vessel aground with the risk of loss due to her back breaking from scouring tides and/or oil pollution what option would you choose? The nickname WAFI came about based on experience.

 

[doug748]

There's absolutely nothing wrong with what you did. You altered course early to avoid a potential collision situation, as advised by the ColRegs. The "don't turn to port" thing applies to collision avoidance situations, i.e. close quarters manoeuvring. If you had stood on with a CPA of only 500metres, that would have been a collision risk situation.

These words should be chiselled in stone and set above the portal.

Two ships on converging courses are not at collision risk till at close quarters.

 

[RobbieW]

There's absolutely nothing wrong with what you did. You altered course early to avoid a potential collision situation, as advised by the ColRegs. The "don't turn to port" thing applies to collision avoidance situations, i.e. close quarters manoeuvring. If you had stood on with a CPA of only 500metres, that would have been a collision risk situation.

What I was trying to question is that ships always follow IRPCS, in my experience they do not. IMO I should have expected the ferry (as give way) to make an obvious turn to starboard to pass astern, when that hadnt happened at 5 miles or so separation I made an obvious turn to avoid close quarters. The question is to some extent where do the boundaries lie for taking avoiding action ?

 

[Uricanejack]

What I was trying to question is that ships always follow IRPCS, in my experience they do not. IMO I should have expected the ferry (as give way) to make an obvious turn to starboard to pass astern, when that hadnt happened at 5 miles or so separation I made an obvious turn to avoid close quarters. The question is to some extent where do the boundaries lie for taking avoiding action ?

My observation, different types of commercial vessels act in different ways. Ferries are typically relatively fast and highly maneuverable. Compared to large freighters. Ferries often operate in congested ad restricted waters.
What a Ferry regards as close quarters and a large freighter regards as close quarters may be two very different points of view.
5 miles to a big freighter might be close. While to a ferry still a long ways off.

I would Ask. If you are going to take the point of view risk of collision does not yet exist. Is it fair to expect the ferry to take the view risk of collision exists? Suggesting the ferry was not following the IRPCAS.

As to where the boundaries lie.
There are no specifics. Its up to you to determine what is reasonable based on your vessels ability to manoeuver.
My questions to you.
Did you take action because it appeared to you the ferry was not taking the appropriate action as required by the rules.?
Or.
Did you take action at long range to prior to risk of collision arising to prevent risk of collision arising?

 

[westhinder]

What I was trying to question is that ships always follow IRPCS, in my experience they do not. IMO I should have expected the ferry (as give way) to make an obvious turn to starboard to pass astern, when that hadnt happened at 5 miles or so separation I made an obvious turn to avoid close quarters. The question is to some extent where do the boundaries lie for taking avoiding action ?

Trouble is that you never know whether the OOW on the bridge has noticed you when you are 6 or 7 nm off. So maybe they did not alter course because they did not know you were there.
It is the reason why I installed an AIS transceiver.

 

[Prasutigus]

Trouble is that you never know whether the OOW on the bridge has noticed you when you are 6 or 7 nm off. So maybe they did not alter course because they did not know you were there.
It is the reason why I installed an AIS transceiver.

And it's the reason I installed an Echomax active radar reflector.

 

[Robin]

Trouble is that you never know whether the OOW on the bridge has noticed you when you are 6 or 7 nm off. So maybe they did not alter course because they did not know you were there.
It is the reason why I installed an AIS transceiver.

Or had indeed seen you and decided there was no risk, by their calculation from a more stable platform with more sophisticated gear.

 

[JumbleDuck]

Absolutely. Which is why you should stop unexpectedly on roundabouts when an artic approaches from your left. How could that cause a problem? It's not as though the colregs have been drawn up up by people who, between them, have thousands of years experience of marine navigation, so why not make up your own rules to which no one else is privy?

And yet all those thousands of years of experience have come up with rules which are incomplete, inconsistent and in places undefined, resulting (for example) in us having a duty not to impede vessels which much give way to us ...

 

[john_morris_uk]

To put it very simply. No.

The next obvious question. Why is an alteration to starboard the recommended practice. If the rules do not give specific direction to alter to starboard.

Which unfortunately is not a short simple answer.

The rules do not apply in isolation. In any given situation rules 1 to 10 apply to all vessels. 11 through 18 to vessels in sight of one and other and when vessels are not in sight of one and other rule 19 applies.

RULE 15 Crossing Situation When two power-driven vessels are crossing so as to involve risk of collision, the vessel which has the other on her own star- board side shall keep out of the way and shall, if the circum- stances of the case admit, avoid crossing ahead of the other vessel.

Although no direction is given to alter to starboard. Direction is given to keep clear and avoid crossing ahead.

RULE 16 Action by Give-way Vessel Every vessel which is directed to keep out of the way of another vessel shall, so far as possible, take early and substantial action to keep well clear.

As you can see rule 16 requires the give way vessel to take early and substantial action to keep well clear.
So back to rule 15. The PDV with the other PDV on her starboard side is required to take early and substantial action to keep well clear and if the circumstances admit avoid crossing ahead of the other vessel.

RULE 2 Re sp o n s i b i 1 i ty (a) Nothing in these Rules shall exonerate any vessel, or the owner, master or crew thereof, from the consequences of any neglect to comply with these Rules or of the neglect of any precaution which may be required by the ordinary practice of seamen, or by the special circumstances of the case. (b) In construing and complying with these Rules due regard shall be had to all dangers of navigation and collision and to any special circumstances, including the limitations of the vessels involved, which may make a departure from these Rules necessary to avoid immediate danger

Rule 2 always applies. Rule 2 requires the practice of good seamen. or common sense. All the time. Usually you will see rule 2 quoted when the situation is one in which common sense requires a departure from the rules. Obviously where there is no special circumstance rule 2 requires the rules to be followed.

To complicate it further. Rule 17

(c) A power-driven vessel which takes action in a crossing situa- tion in accordance with sub-paragraph (a)@) of this Rule to avoid collision with another power-driven vessel shall, if the circumstances of the case admit, not alter course to port for a vessel on her own port side.

Rule 17 C by giving direction to the stand on vessel not to alter course to port for a vessel on her own port side. This implies a give way vessel will alter course to starboard.

The implication is both vessels by altering to starboard will not alter towards each other. The will alter away from each other.

back to rule 2

So back to rule 15. The PDV with the other PDV on her starboard side is required to take early and substantial action to keep well clear and if the circumstances admit avoid crossing ahead of the other vessel. Add the requirements of rule 2. Apply the practice of good seamen. Without a special circumstance requires The give way vessel to take . The simple best action to keep well clear and avoid crossing ahead is an early and readily apparent alteration of course to starboard to pass astern of the stand on vessel.

Simple really an alteration of course to starboard to pass astern is just plain old common sense unless there is some kind of special circumstance.

Clear as Mudd?

A rather more elegant and eloquently argued answer saying what I was trying to say earlier!

(PS I really wonder why people make such a meal of this; know the rules and apply them in a seamanlike way isn’t really very difficult IMHO. I agree that there are interesting discussions to be had regarding the application of IRPCS but I suggest they don’t involve simple crossing situations.)

 

[JumbleDuck]

These 3-way encounters like that do have the makings of a Mexican standoff !!

One of the many weaknesses of the IRPCS is that they assume that only two vessels are ever involved and completely ignore the possibility that a vessel coul dbe simultaneously give-way and stand-on to two others.

 

[capnsensible]

And yet all those thousands of years of experience have come up with rules which are incomplete, inconsistent and in places undefined ...

Only for pedants. They are great for sailors.

 

[john_morris_uk]

Only for pedants. They are great for sailors.

Truth the sailor speaks.

 

[JumbleDuck]

Only for pedants. They are great for sailors.

They work pretty well in most situations, but in a significant number they require fudging. JFM has written some very interesting stuff about case law in this area in the MB forum. That's where I learned that standing on does not necessarily mean maintaining course and speed.