Q.Why the give way vessel in a crossing situation shall if the circumstance admit avoid crossing ahead of the other vessel ?

I have heard many explanations for why the give way vessel in a crossing situation shall avoid crossing ahead of the other vessel. The most common explanation I hear is that you do not want to be in direct line with a vessel approaching towards you.

But all these explanations do not make any sense. You know why?

Because in a crossing situation, one vessel has to cross ahead of another vessel.

If the give way vessel passes astern of the stand-alone vessel, then the stand-alone vessel is passing ahead of the give way vessel.

Then why it is preferred for the give way vessel in a crossing situation to not to cross ahead of the other vessel?

There are few logical reasons.

1) It is easier to make out if the vessel will pass clear

The first reason is that it becomes easier for the give way vessel to make out if the vessel will pass clear of the other vessel. The give way vessel just have to alter course to aim for the stern of the other vessel.

Look at this picture. Without giving any other data or values I will ask you this question. Will the give way vessel pass clear of the other vessel after alteration of course as indicated in the below picture?

I am sure your answer would be, Yes the vessels will pass clear for sure. But now let us see the same situation with give way vessel passing ahead of another vessel.

Well, in this case, the answer would be, the vessels may pass clear or may not pass clear.

2) The time for the vessels to cross

If the give way vessel tries to pass ahead of another vessel, the whole crossing situation will take more time to complete. But if the give way vessel passes astern of the other vessel, the give way vessel will be able to cross in comparatively lesser time.

Why is this important?

This is important because as a give way vessel, we want to alter the course, pass the other vessel and come back to our course quickly.

3) CPA is close to the Bow crossing range

In a crossing situation, if the give way vessel tries to pass ahead of the other vessel, the CPA will be closer to the bow crossing range.

This means that in this case when the give way vessel is right ahead of the other vessel, the vessels may be too close to each other.

Unless you are maintaining a good CPA of more than 1.5 NM, this situation can scare the hell out of the give way vessel.

The give way vessel may find the other vessel too close visually which may prompt a wrong action from either of the vessels in the last minute.

On the other hand, if the give way vessel passes astern of another vessel, the bow crossing range would be much earlier than the CPA. So both the vessels would have crossed each other before the CPA and at the time of CPA, both the vessels would know that the distance between them is increasing and there is nothing to worry about it. 

Visually this is not a very disturbing picture as with the give way vessel crossing ahead of another vessel.