The problem of avoiding collisions at sea, particularly in restricted visibility, is not likely to have one simple solution. Indeed there are three main areas which need separate consideration because of their different requirements. First, in rivers and estuaries, port approaches and narrow passages traffic is rigidly confined. Second, in waters adjacent to coastlines and in some other areas dense traffic has limited space in which to manœuvre. Third, in the open sea there are fewer encounters and unlimited manœuvring space. It seems probable that the best solution to the first of these problems will be found in shore surveillance of the traffic and regulation of the traffic flow by a licensed authority. Prescribed routes with perhaps speed limits and policing may solve the second, but only ratification of an internationally accepted rule of behaviour will satisfy the third requirement. This paper proposes to develop a set of manœuvres which may be applied as a rule which will be accepted as a possible solution to the third requirement.