The Next Advance in Enhanced AIS Collision Avoidance

No link, my idea, remember you saw it here first.

On the APRA the mate on watch clicks on a target’s AIS display and from a menu selects either “red to red” or “green to green”. The AIS for that target then displays a “pending” symbol.

On the target ship an audible sounds, the target ship mate either selects “accept” or not.

If the target ship mate selects “accept” for say “red to red” own ship’s AIS changes from “pending” to “red to red”. . All the ships which are considered as risk of collision will show either “r to r” or “g to g” on each ship’s display.

No confusion, no bs on the VHF.


I think you need to remove the word ‘avoidance’ from the thread title here to make it more reflective of what will happen.

Totally feasible with today’s technology.
PS> As long as the other ship doesn’t belong to the US Navy, that is.

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Technology is wonderful.
Advancing from Radar Assisted Collisions to AIS Assisted Collisions in just a few decades! :slight_smile:


If a system like this replaced passing arrangements via VHF it would be lower workload and less ambiguity. On the other hand if it were used as a replacement for the signal sent by an early and substantial course change that would have a negative impact.

Be difficult to test in actual use.

I have noticed that with ARPA ships more frequently changing course early to avoid a risk of collision and ships close making small corrections to maintain the desired the CPA. This tends to blur the distinction between when risk of collision exist and when it does not.

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Mates can spend more time with their faces in the ARPA instead of the window. What could go wrong?


There should never be any need for ‘passing arrangements via VHF’


There should never be collisions at sea.

Pre-ECDIS and so forth before port arrival we used to use the paper chart for information needed by the watch mate. For example mark the spot where to call the captain, where to begin the load down program, where and what channel to use to call traffic, pilots , port control etc.

If the goal was to reduce the time the mate spent looking at the charts that information could have been left in original form, the mate could dig through the pubs, the night orders to find it. But reducing time spend looking at the chart is not the goal. The goal is to reduce the total amount of time needed to find and process the information needed.

Sensory overload.

Here is an article about text system commercial air uses to avoid the inefficiencies and risk of error using VHF

The traditional way of communicating about the plans and any changes can be tedious. First the controller calls the cockpit, verbally ticking off the details. Then, the pilot has to verbally confirm the plan, and enter the information manually into the plane’s flight management system.

"So it’s a bit like you’re calling your friend,’’ Huerta explained. "You’re asking for directions to his house, you’re writing down what he tells you, there’s a lot of back and forth discussion . . .and before you know it 15 minutes have gone by and you still haven’t left the house.’’

With Data Comm, air traffic controllers click a button to transmit the flight plan to the cockpit. The pilots look it over then push a button to say the plan has been accepted, and the information is automatically logged in the flight management system.

It’s about reliable and accurate transmitting of information with minimum distraction from task.

I am aware that in places the VHF is overused.

What is it with everyone & VHF, just follow the damn rules as they are written.


Not never, but hardly ever and virtually never at sea rather in in restricted waters.

Everybody? In a risk of collision situation own ship might find itself obligated to maintain course and speed. If for whatever reason that can’t be done, for example weaving around ferries, fishing vessels and coasters when encountering another large less maneuverable vessel it is sometimes prudent to verify intentions.

For example perhaps leaving/arriving Pusan or Laem Chabang.

Seems like it would be difficult to be unaware of all the material published warning about the use of VHF for collision avoidance. Nonetheless people are eager to bring it up.

Here is MGN 167 (M + F), I think it’s been toned down a bit from the original.


Although the use of VHF radio may be justified on occasion in collision avoidance, the
provisions of the Collision Regulations should remain uppermost, as misunderstandings
can arise even where the language of communication is not a problem

MGN 167 (M + F)
Dangers in the Use of VHF Radio in Collision
Note to Ship owners, Masters, Skippers, Officers and Pilots of Merchant Ships, Yachts and Fishing
This note supersedes Marine Guidance Note MGN 27 (M+F)

  1. There have been a significant number of
    collisions where subsequent investigation has
    found that at some stage before impact, one or
    both parties were using VHF radio in an
    attempt to avoid collision. The use of VHF
    radio in these circumstances is not always
    helpful and may even prove to be dangerous.

  2. Uncertainties can arise over the identification
    of vessels and the interpretation of messages
    received. At night, in restricted visibility or
    when there are more than two vessels in the
    vicinity, the need for positive identification is
    essential but this can rarely be guaranteed.
    Even where positive identification has been
    achieved there is still the possibility of a
    misunderstanding due to language difficulties
    however fluent the parties concerned might be
    in the language being used. An imprecise or
    ambiguously expressed message could have
    serious consequences.

  3. Valuable time can be wasted whilst mariners
    on vessels approaching each other try to make
    contact on VHF radio instead of complying
    with the Collision Regulations. There is the
    further danger that even if contact and
    identification is achieved and no difficulties
    over the language of communication or
    message content arise, a course of action might
    still be chosen that does not comply with the
    Collision Regulations. This may lead to the
    collision it was intended to prevent.

  4. In 1995, the judge in a collision case said “It is
    very probable that the use of VHF radio for
    conversation between these ships was a
    contributory cause of this collision, if only
    because it distracted the officers on watch
    from paying careful attention to their radar. I
    must repeat, in the hope that it will achieve
    some publicity, what I have said on previous
    occasions, that any attempt to use VHF to
    agree the manner of passing is fraught with
    the danger of misunderstanding. Marine
    Superintendents would be well advised to
    prohibit such use of VHF radio and to instruct
    their officers to comply with the Collision

  5. Although the practice of using VHF radio as a
    collision avoidance aid may be resorted to on
    occasion, especially in pilotage waters, the
    risks described in this Note should be clearly
    understood and the Collision Regulations
    complied with.

I think in some cases where the blame was put on the VHF it was just part of loss of situational awareness and meltdown. Sometimes VHF calls are made as a last resort.

I find that I get a lot of VHF calls from the give way vessel when I’m the stand on vessel asking what my intentions are. I typically respond “I plan to carry on this course and speed if you don’t mind.” There does seem to be a fundamental lack of understanding the COLREGS at the heart of the problem.

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Yes, in some areas there is lot of BS on the VHF, most of the mates I get don’t use the VHF if it’s not needed. Why would you call in a clear cut case? I guess that’s the point people are trying to make.

Some mates that have never sailed foreign think there going to make simple arrangements on VHF. I tell them show don’t tell, make a substantial course change.

Having said that, how much sense would it make not to call in a situation where it significantly reduces risk? For example I want to pass port to port but can’t keep a red light on another ship because of weaving through F/V traffic in a tight spot.

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The issue is what if it’s not possible to make a course change that is early and substantial? Or in the case of stand-on, sometimes it not possible to maintain course and speed.

That’s what I don’t understand about the "just follow the COLREGs argument. Did the mariners (??) that make that argument spend their entire careers only meeting one other vessel at a time? Are they able in every case as stand-on to maintain course and speed? Is all their experience in mid-ocean?

In a COLREGs situation when risk of collision exists a substantial course is intended as a signal of intention. Is that course change going to be in every single situation an adequate signal without ambiguity?

A collision at sea is a low probability, high consequence event. There are some situations that arise at sea where the watch officer judges that due to the circumstances of the case the signal sent by the course change alone does not reduce the risk of collision sufficiently.

Not every situation at sea is as clear-cut as the text book.


Integrating unambiguous passing intentions into ARPA (and AIS) is a great idea.

I don’t know how well it would work in practice.

Here is MAIB’s list of problems with using the VHF:

2.Uncertainties can arise over the identification of vessels and the interpretation of messages received.

3.Valuable time can be wasted whilst mariners on vessels approaching each other try to make contact on VHF radio

4, In 1995, the judge in a collision case said “It is very probable that the use of VHF radio…it distracted the officers on watch from paying careful attention to their radar

Even if the plan is 100% to comply with COLREGs there is still often a need to signal intention. Traditionally this is done with an early and substantial course change.

I wonder if the “dance of death” was a factor in the recent tanker collision?