99052 Why Overtake on the Port Side?

Why Overtake on the Port Side?
Report No. 99052

Having just cleared Pulu Rondo, I was on a course of 2690T and was being overtaken slowly by a car carrier. As the difference in speed between us was less than 1 knot, the situation had been developing for some time. The car carrier shaped up to overtake me on my port side and, observing that she was passing closer than I felt was comfortable (0.5 miles confirmed by ARPA), I called him on the VHF and asked his intentions. I told him that I thought 0.5 miles was unnecessarily close to overtake when there were hundreds of miles of room on both sides and in a situation where he was liable to encounter eastbound traffic ahead requiring him to go to starboard.

I pointed out that as an overtaking vessel he was obliged to keep clear of me until he was past and clear. In his reply the OOW said that he would alter course to port which he duly did. While this improved the situation as far as I was concerned, it did leave him in a poor situation with regard to eastbound ships. This became obvious soon afterwards when he encountered a tanker right ahead of him on a reciprocal course. He was then forced to alter further to port and pass to starboard of the approaching ship. I would suggest that, in the period of one hour, the car carrier put herself and two other ships at risk through not having sufficient understanding of the "Rules". I would further suggest that, in the general strategy of avoiding collision, the tactical approach to overtaking is to overtake on the starboard side of the vessel being overtaken. This leaves the overtaking vessel with clear water to starboard to use for her own manoeuvring or to keep clear of the overtaken vessel if she has to go to starboard.