If you had to categorize the root causes of most collisions today, you would come up with two broad categories:

  • Poor lookout;
  • Inappropriate avoiding action.

Poor lookout

People forget, and perhaps during the training process there is not enough emphasis on, the provisions of Rule 5:

Every vessel shall at all times maintain a proper look-out by sight and hearing as well as by all available means appropriate in the prevailing circumstances and conditions so as to make a full appraisal of the situation and of the risk collision.

Avoiding collisions is a three-stage process which is contained in Rules 5, 7, and 8:

  1. Detect and observe the approach of the other vessel;
  2. Appraise the situation and the risk of collision;
  3. Take timely and avoiding action.

In order to have sufficient time to properly appraise the situation and in which to take effective avoiding action, a vessel needs to be proceeding at an appropriate – or safe – speed; and Rule 6 sets out the factors to be considered when determining what is a safe speed. Sadly today, notwithstanding all the increased navigational aids, I fear there is a still a reluctance to slow down and a failure to properly use these navigational aids to properly appraise the situation.

The key to making a proper appraisal is early detection. We have AIS now and the radar horizon is greater than the visible horizon, but people are still failing to make proper use of these navigational aids.

As Mr. Sheen J. said back in 1989:

The greater the distance at which an approaching ship is detected the greater is the chance of making a proper appreciation of the situation and of avoiding a close quarters situation.

And as the Court of Appeal said back in 1973:

A good look-out also involves the intelligent interpretation of the data received by way of …various scientific instruments

In addition, a full appraisal requires a proper understanding of three things which are not defined in the Collision Regulations because they will differ according to the circumstances:

  • What is a safe passing distance?
  • What constitutes risk of collision?
  • What is a close quarters situation?

Too many mariners, I think, consider risk of collision to mean risk of actual contact, and assume there is no risk of collision if the vessels are not going to hit each other; that is, if they are passing clear even at a close distance. As a matter of English law however, a passing distance in clear visibility of anything less than 5 cables is going to leave you in trouble in court. To be safe, vessels should be aiming for a passing distance of a mile or more in good visibility and open waters, and in restricted visibility vessels should double that distance.

Under English law, risk of collision exists when there is a possibility of a collision; the risk is not limited to situations where there will be actual contact if neither vessel does anything. If the vessels are not going to be passing at a safe distance these is risk of collision.

A close quarters situation is a little bit more complicated, but the reported cases suggest that the give-way vessel should be taking avoiding action in open waters at least 12 minutes or more before collision. So, if the TCPA reduces to 12 minutes in open waters, I would suggest you are now in a close quarters situation.

Inappropriate avoiding action

During the teaching process there is not enough emphasis perhaps on the wording of Rule 8a in particular:

Any action to avoid collision…shall, if the circumstances of the case admit, be positive, made in ample time, and with due regard to the observance of good seamanship

“Positive” means an alteration of course or speed which is large enough to be readily apparent to another vessel observing visually or by radar. I fear too many mariners today are using their ARPA to work out what is the minimum alteration necessary to increase the CPA by a couple of cables. As a matter of English law, “positive” action means an alteration of at least 30 degrees or more in restricted visibility; and whilst alterations of course are much more readily apparent today with ARPA, anything less than 20 degrees in clear visibility is unlikely to be sufficient. It is certainly arguable that anything less than 20 degrees will not be readily apparent visually.


“Made in ample time” means in sufficient time to avoid a close quarters situation and enable the vessels to pass at a safe distance. Understanding what is a close quarters situation therefore, is part of the problem today in the appraisal process. If you accept that a TCPA of 12 minutes in open waters means you are now in a close quarters situation, then “made in ample time”  means taking action at least 12 minutes before collision. Too many mariners today, I believe, are still thinking in terms of distance rather than time. They delay taking avoiding action until the other vessel is say 2 miles away; but if the combined speed of approach is 40 knots, you’ve just allowed yourself only 3 minutes to get out of the way of the other vessel.

As for “good seamanship”, it is still the tendency today of too many mariners to rely upon the VHF for collision avoidance. There are circumstances when the use of the VHF for collision avoidance is appropriate, and as has been judicially noted, the courts rarely hear of circumstances where the VHF has been so used to advantage. But many mariners mis-use the VHF to discuss a method of passing which is not in accordance with the Collision Regulations, or appear to place total reliance upon it. By way of illustration, the following is from a Shipmaster’s Incident Report of his passage through a busy traffic area, where it appeared he discussed the method of passing with every other vessel that he met; that is, he appeared to place total reliance upon VHF to avoid collision:

We advice AS that we will pass on her Stern at 0243H LT, after passing her stern We contacted HP to pass port to port. At 0248H LT we contacted M that we will pass on her stern. At 0252H LT we contacted H & SC to pass port to port. At 0255H LT contacted SS to pass port to port. We contacted B to pass port to port but no reply. We contacted B many times on Ch.16 but still no reply. We trying to informed her to altered course to her Starboard to pass port to port but no reply.

The mariner has many more navigational aids today to assist him in avoiding collisions at sea, but I fear too many mariners are not making proper and effective use of these aids, and do not have a proper understanding of what constitutes a safe passing distance, risk of collision, and a close quarters situation.


Above text is an edited version of Mr. Hirst’s presentation during the 2019 SAFETY4SEA Singapore Forum.

View his presentation herebelow

The views presented hereabove are only those of the author and not necessarily those of  SAFETY4SEA and are for information sharing and discussion purposes only.

Harry Hirst, Partner & Master Mariner, Ince & Co

Harry Hirst went away to sea after leaving school in 1975 and qualified as a Master Mariner in 1988. A graduate in both Nautical Studies and Law, he qualified as a solicitor in England in 1992 and has spent his entire legal career specialising in Admiralty law. He specialises in all aspects of Admiralty law including collision; salvage, total loss and wreck removal; pollution; fire and explosion; cargo shift, loss and damage; and general average.