When considering what equipment is to be fitted either in the ship or ashore in order to ensure safe navigation in conditions of high traffic density, we can to some extent be guided by looking at what has happened in the aircraft world where these problems have been present for a long time. Here considerable use is made of radar and of radio navigational aids. Before assuming too readily that the same will apply in the marine world, we should perhaps recall that radar and the hyperbolic radio aids were born during World War II, and that since then fundamentally new techniques in navigation have been developed which should be examined to see if they have any bearing on our present problem.