Reason
The "Yuyo Maru No. 10", laden with a total of 47,476 MT of light naphtha, propane and butane, left Ras Tanura Saudi Arabia, for Kawasaki, the port of Keihin, on October 22, 1974.
On November 9, the Master of the "Yuyo Maru No.10", examinee, went up to the bridge at a position about 2 miles NW of Izu O Shima lighthouse to take the con. The vessel met the escort boat "Orion" around a position of 180, 1 mile from Uraga Suido Traffic Route No. 1 center light buoy. She was displaying over the bridge a black cylinder showing she was a huge vessel, and international code flags consisting of a first substitute and "B" in a vertical line with a flashing red light on the radar mast, indications of a ship carrying dangerous goods. He employed as his assistants the Second Officer, who was in charge of the watch, the Third Officer and the Junior Third Officer, both examinees; the Second Officer mainly engaged in radar watch, the Junior Third Officer in communication with the "Orion", and the Junior Third Officer in the handling of the engine telegraph. Furthermore, one sailor was being assigned as a lookout, in addition to the quartermaster at the helm. The vessel was proceeding with the "Orion" placed no more than 1,000 m ahead fine on her starboard bow.
When she paralleled Naka-no Se No. 1 light buoy port abeam at a distance of about 200 m off the buoy at about 13:18 hours, the Master of the "Yuyo Maru No.10" though aware that her harbor full speed was higher than that of the "Orion", continued sailing at this full speed, considering that there was no speed restrictions in the Naka-no Se Traffic Route and that there might be no large vessels coming into the route in a head-on situation since the route is for one-way traffic.
However, even if there was no possibility in the Naka-no Se Traffic Route of encountering a vessel in a head-on situation, she might meet a vessel sailing out of the Kisarazu Passage in the vicinity of the north extremity of the Naka-no Se Traffic Route. It was, thus, vital to ascertain the presence of vessels coming out of the Kisarazu Passage through the sufficient utilization of the "Orion" as a course guard boat by placing it about 1,000 m ahead of her, as well as strengthening radar watch. The Master of the "Yuyo Maru No.10" continued sailing at harbor full without giving special instructions to the Second Officer at the radar nor reducing her speed, thus narrowing the distance to the "Orion".
Slightly past 13:31 hours, following the receipt of a report from the Second Officer on the presence of a crossing vessel on her starboard side, the Master who was taking in control at the forward midship portion of the bridge, sighted the "Pacific Ares" slightly less than 38｡?n her starboard bow 1.5 miles off and took alone the bearing of the vessel on the compass. The Junior Third Officer confirmed by watching through binoculars that the other vessel was in transit, and cutting waves at the bow, and reported to the Master to that effect. The Master had the Junior Third Officer sound a long blast on the whistle and watched the other ship's compass bearing, expecting that she would take evasive action. He did not feel that there was a clear change in compass bearing and judged that the other vessel was heading almost for Tokyo Bay Naka-no Se D light buoy and that the courses of both vessels crossed outside the boundary line of the Naka-no Se Traffic Route.
