Averting risk by 'all available means'

Captain Trevor Bailey asks what exactly is meant by ‘all available means’ when it comes to collision avoidance.

“Every vessel shall use all available means appropriate to the prevailing circumstances and conditions to determine if risk of collision exists. If there is any doubt such risk shall be deemed to exist.” Colregs, Rule 7 

We determine risk all the time: when walking down a crowded street, we tend to be instinctively aware if we are going to walk into somebody or if they are going to do the same to us. As professional navigators, we should be able to apply this same inherent sense to our watch-keeping and lookout practices; with experience there will often (though not always!) tend to be an instinctive awareness of the potential of risk of collision with another vessel. 
Yet instinct is far from the only way of determining the risk of collision. So, how should you interpret “all available means”? What do you have at your disposal to determine risk of collision? 
The primary tool should be the ‘mark one’ eyeball, assisted by the compass repeater. On some vessels this may be placed on the centreline of the wheelhouse, although this is not universal by any means. 
A regular and careful check of the compass bearing of any approaching vessel will give the navigator an early and effective indication of the potential risk of collision. Bear in mind there must be an appreciable change in the bearing before you can be confident

Look out for the lookout
Of course, with reference to visual checks on the approach of other vessels (or your approach to them if you are the overtaking vessel), as OOW you should also make use of the lookout. The job title is a bit of a giveaway, plus he or she is required by Rule 5 of the Colregs! The lookout is there to assist and it is essential that you establish a good rapport and demonstrate your trust in them. Acknowledge reports courteously. Don’t dismiss them with, “Of course I’ve seen that vessel!” 
They are only doing their job. If the lookout feels ignored or not trusted, they may choose not to report… and maybe you haven’t seen that vessel after all.

Changing course
If you do need to take avoiding action to avoid risk of collision, you have a number of tools available. Use them wisely. If you choose only to alter course, it is good practice to engage hand steering, using the lookout as helmsman. Do not take that role yourself; you will be limited in your ability to multi-task by steering and monitoring the compass bearing. 
You may decide to use the autopilot, but do so with care. It may be tempting to make a series of small alterations on the autopilot to avoid large rudder angles, but that series of small changes will not be readily apparent to the other vessel. An appropriate significant alteration of course in hand steering can be achieved without resort to large rudder angles.

Safe distance
Be aware of what the equipment is telling you and how to interpret that information. Know your own vessel and its limitations. In open waters, I would caution against passing any vessel at less than one mile ahead or abeam and not less than half a mile astern. Remember Rule 8 (d): 
“Action taken to avoid collision with another vessel shall be such as to result in passing at a safe distance. The effectiveness of the action shall be carefully checked until the other vessel is finally past and clear.” 
You cannot second guess what the OOW on the other ship is thinking and he or she may not consider that smaller margins are acceptable. They might start calling you up on the VHF and then who knows what might happen? 
The VHF is NOT there to avoid collision: the concept of the ‘VHF-assisted’ collision is not just a myth. It is a proven reality, as many accident reports clearly demonstrate. The communications between ‘ship on my starboard side’ and your own ship must be avoided at all costs. 
In a recent passage through the Dover Strait, north-east bound on a laden VLCC in the Deep Water route, my own ship, Nonsuch, was called by an overtaking vessel, Overtaking Express, on the VHF. The conversation went something like this: 

Nonsuch, this is Overtaking Express on your stbd quarter. What are your intentions? I am overtaking you.

Overtaking Express, this is Nonsuch. I intend to comply with the Colregs and maintain my course and speed.

Nonsuch, this is Overtaking Express. I will come past you on your stbd side.

Overtaking Express, this is Nonsuch. I shall be maintaining my course to the stbd side of the channel and I suggest that you pass on my port side.

[In dejected voice] Nonsuch, this is Overtaking Express. That will mean I have to adjust my speed and slow down to come across your stern. 

He did adjust his speed, altered course around our stern and then overtook on the port side. 
Like VHF, AIS is NOT to be used in isolation for assessment of the risk of collision, even though it does provide CPA and TCPA. It was developed to provide additional and improved situational awareness. It may be helpful to provide an indication of another vessel’s intentions, particularly in busy and complex traffic areas. 
Through integration, more information is available to the OOW than was previously the case and, for vessels already fitted with ECDIS and/or ECS, it is quite likely that radar and AIS data can be overlaid on to the chart display. If so, the OOW may be able to interrogate these targets directly in the ECDIS / ECS but should not rely on this information alone to determine the risk of collision.

Targeted plotting
Recognise your own temptation to ‘plot everything’. A radar plot looking like chickenpox is unprofessional and suggests that you do not have a good appreciation of your surroundings. Your radar will be able to display trails of all targets and these should give a further indication of the likelihood of the risk of collision. You can then decide which targets need plotting.
Once plotted, use the radar controls such as vector length or relative versus true vectors to gain a better appreciation of the situation.

Technical detail
As OOW you must not be constrained in your choice to use the engines to control your speed, if it is appropriate. An early alteration, if there is sufficient sea room, may well be the most effective course of action to avoid the risk of collision but, in more confined areas, it may be desirable to adjust the ship’s speed. Be aware of restrictions on changes in the operation of engines, particularly slow speed engines, but it may be that the notice to engineers regarding changes is partly for their convenience rather than strictly mechanical. The telegraph is there to be used. 
Radar and ARPA are excellent tools to assist with determining risk of collision but it is essential that you are aware of the limitations of the equipment. After all, it relies on highly sophisticated computer hardware and software to make the calculations and observations for you. The fact that it is “Type Approved” implies that it has been tested to ensure compliance with the Performance Standards specified by IMO and the IEC. However, that approval was carried out under test conditions and the navigator must check the equipment is working effectively at regular intervals.