#COLREGs – Rule 15

You’ve seen me reference Captain George Eldridge’s navigation poem before.  What did he have to say when two boats are about to cross each other’s paths?    

                   “But if to starboard Red appear,

                         it is my duty to keep clear – to act as judgment says is proper,

                     to port or starboard, back or stop her…” 

This column is all about that…


As noted prior, there are only three conditions of vessels meeting on the waters – head-on, crossing or overtaking situations.  The Rules govern how the skippers are to interact with each other through helm control and sound (or radio) signals.  This is about two power-driven vessels about to cross each other’s paths – a possible collision course.

Rule 15 – Crossing Situation

When two vessels appear to be heading across each other’s paths, this is by definition a crossing situation – and, like in your car – a collision needs to be avoided!  But how can you tell if you are actually on a collision course.  There are 3 ways – with the 3rd method, as usual, always winning out:

  1. At night, if you see a red light and a white light above it and trailing behind, you are crossing each other’s path and she is the stand-on vessel.  You are thus the give-way.  If you see a green and a white light above it and trailing behind, you have a crossing situation where you are the stand-on vessel – but keep an eye on her always!  You don’t want to be “dead right!” 
  2. During the day, you can obviously see if the vessel is crossing your path on your starboard side (you are give-way) or on your port side (you are stand-on.)
    Mark the other boat’s progress against something fixed on your boat – a cleat, a stanchion, the anchor – anything that is traveling with you.  If the opposing boat continues to hover on or around that fixed mark as you both continue your course and speed, a collision is about to happen!
  3. When in doubt, assume you are on a collision course and act accordingly.

In this situation, the give-way vessel is, by preference, to turn to starboard (towards the stand-on boat) and go behind her (go “under her stern”).  Remember – take “early and substantial” action so that your maneuver is “telegraphed” to the other skipper.

But what if you see that you cannot turn to starboard because of (1) traffic conditions, (2) rocks, (3) shallows, etc…?  Rule 15 clearly says that the give-way vessel “shall avoid crossing ahead of the other vessel”, i.e., do not speed up and try to cross ahead!  The stand-on skipper may be doing the same thing because he hasn’t seen you take early and substantial action to keep clear of him!  If you don’t have substantial time and distance to telegraph such a proper maneuver, just slow down or even stop!  Let the approaching vessel pass ahead of you, just as you would allow a sail boat to pass ahead.

Well, this seems pretty easy – if she is on my right, she goes ahead.  So, what’s the catch?  

Naturally, there are (at least) three catches:

  1. What if a vessel constrained by the nature of their work (say a dredger or a commercial fishing vessel) is on your port side?  You are on their right so you should go ahead, no?  No.  #COLREGs-RULE18 comes into play.  Any power-driven vessel approached on its port side by a hampered vessel must keep clear. You can increase speed to pass ahead though, if conditions clearly permit.
  2. If you are crossing a narrow channel, #COLREGs-Rule9  (d) governs.  “A vessel shall not cross a narrow channel or fairway if such crossing impedes the passage of a vessel which can safely navigate only within such a channel or fairway.”  How can you tell the other boat can’t navigate outside the channel?  Assume the worst…
  3. Lastly, if you are in a “traffic separation scheme”, and if you fish the Canyons you may be, #COLREGs-Rule10 (j) prohibits a boat of less than 20 meters (roughly 65 feet) from impeding the safe passage of a power-driven vessel following the traffic lane.

Boats claiming the special rights implied above must by shapes or lights declare those rights.  If she doesn’t, it will matter to the Admiralty Board when you both appear to explain how you ran into each other… but, remember, it is never 100-0!