Queen Elizabeth I when enunciating the doctrine of freedom of the high seas said ‘…the use of the sea is common to all…’. Until very recently a more appropriate phrase might almost have been ‘a free for all’ for, except for the internationally agreed Rules for the Prevention of Collisions at Sea and the demands of safe navigation to avoid stranding, the seas were free for all to sail as and how they pleased. However, rapid advances in technological development in the last decade or so, combined with changes in transport economics and national ideologies, have brought about dramatic changes in the sea transport industry—both in the size and speed of vessels and in the nature of the cargoes they carry. Inevitably the risk and seriousness of accidents has increased proportionately and in some cases become so intolerable, both socially and economically, that the public attitude towards the traditional freedom of the sea began to change and that freedom was curtailed.

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.

In assessing the human problems which may occur in the development of a traffic system in an offshore area, some lessons may be learnt from the work which has been done on the similar problems arising in port approaches. There are several fundamental differences between the port and offshore problems such as the direction and density of traffic flow, the parochial as opposed to the international legislation and the difficulties that attend the positive identification of passing traffic. These considerations mean that it must not be supposed that the solutions which have been discovered in the port approaches may be simply transferred to the offshore case, but the similarity of aims in the two systems make a comparative study worthwhile. Basically, each authority must first legislate to allow control and guidance of the traffic. From this right to control must stem the obligation to organize the traffic into a scheduled stream, but this regulated stream will only reduce the risk of conflict if the schedule can be maintained by surveillance, communication and the cooperation of the mariner.

This conference is looking at a range of issues having a bearing on the flow of traffic and the safe conduct of vessels at sea. It seems clear from many of the papers that more needs to be known of the manner in which ships react one with another and, by implication, regulation of traffic at sea can no longer be a matter within the sole competence of the experienced and dedicated mariner, as it has been in the past. If optimum safety is to be achieved, both the mathematician and the operational research expert will also have their parts to play in assessing the merits of possible solutions.

The publication by the Hydrographic Department on 4 February 1972 of 23 new metric charts of the south-west coast of England was announced in Notice to Mariners 264 of 1972. This is a significant first step towards the metrication of all charts of the British Isles of which there are about 400, a programme that should be complete before 1980. The block areas with tentative dates for completion are shown in Fig. 1.