200133 Crossing a TSS

Crossing a TSS
Report No. 200133

It was daylight and the visibility was in excess of 5 miles. Own vessel was in a TSS steering 0410 at 21 knots and we were overtaking a coaster which was about 1 mile away on our starboard bow.

A westbound ferry on a course of approximately 2700 and steaming at 15.5 knots was approaching the TSS. Her relative track showed that she would pass clear astern of us with a CPA of 1 mile and no other traffic astern of us to worry her.

When the ferry arrived at the eastern limit of the TSS she altered to starboard to 3100 putting herself onto a collision course with own ship (3.5nm away) and the coaster (less than 3nm away). In response to a VHF call she confirmed that her intention was to cross the TSS at right angles.

I made a rapid alteration of course of 300 to starboard to pass around her stern and the coaster did the same. It was fortunate that the visibility was good as this helped with easy identification. In bad visibility the situation could have been very confusing.

In this incident, the intention to comply closely with the Collision Regulation 10c is not to be blamed. However, complying with the Rule is conditional on ensuring that in doing so, a clearing situation does not turn into a close quarters situation. It would be far more sensible for a vessel intending to cross a TSS at right angles to alter to the new course whilst still 3 or 4 miles away from the TSS. This would permit vessels proceeding in a traffic lane to analyse the crossing vessel's course and to take the appropriate action.