The need for measures to guide shipping in congested waters to reduce collision risk has received a very considerable amount of attention over the past few years. The Safety of Life at Sea Conference in 1960 recognized the danger of collision in congested areas and required ship owners to formulate ways whereby some measure of control of traffic could be introduced with a view to reducing collision risks. Shell Tankers accept this responsibility and are, therefore, anxious to make some contribution towards the solution of the problem.

Many valuable papers on the subject have been published in professional journals recently. Most of the authors have emphasized the difficulties in which Masters are placed when called to navigate their ships through heavy traffic in reduced visibility, and Calvert in his study of the collision-avoidance problem reached a first conclusion that whatever might be done to improve anti-collision manœuvring, there was an urgent need for regulation of traffic in areas of congestion.