The following paper was presented at a meeting of the Institute held in London on 21 February 1979 with the President, Captain R. Maybourn, in the Chair. It considers some of the factors which apply in the context of overall safety and the weightings which they should be assigned in estimating the optimal speed for ships in given circumstances and conditions.

In air traffic control the speed of individual aircraft cannot be significantly varied without unacceptable economic penalties, or the aircraft falling out of the sky. In the case of ships the speed is a useful variable for traffic management and individual ships can choose, or be assigned, any value between zero and their normal service speed. The following discussion concerns the choice of a suitable speed for marine traffic in terms of safety criteria.