The coastal traffic round Japan proper is an essential part of her communcation system. Transportation. (a) Tankers. After allowing for the requisitioning of commerical tankers by the Japanese navy for service with the fleet, the tanker tonnage at Japan's disposal is only just sufficient to cover the essential imports. Provided the current rate of tanker sinkings is maintained, no appreciable increase in size of the tanker fleet is anticipated. (b) Other Shipping. After allowing for ships requisitioned by the navy, under repair and engaged in essential trade and supplying current needs of the forces abroad, it is estimated that the Japanese have a margin of about 500,000 g.r.t.