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.