A review of the past fourteen years' work in marine safety systems shows many major advances in fulfilling basic requirements. Characteristics of five complementary systems are compared. There are four basic marine safety requirements that, properly implemented, substantially improve safety in marine navigation and expedite the movement of ships. These four requirements, which I had the opportunity to set forth in 1950,1 and all of which could have been met even in 1950, are as follows: 1. The navigating officers of a ship should be able to detect both the relative and absolute position of all other vessels with which there is danger of collision. This calls for an adequate ship's radar. 2. It should be possible for the ship's navigating officers to establish contact and intercommunicate almost instantaneously with their counterparts on other ships within a range of at least 20 or 30 miles. Also, the same capability should exist between ships and shore stations concerned with supplying navigational and operational information or the control of marine traffic. 3. When there is intercommunication between the officers of two vessels within radar range, it should be possible for those on either vessel to identify on the radar scope the response representing the other regardless of the presence of a number of vessels in the immediate area. 4. The navigating officers of a ship should know the ship's position at all times. The degree of accuracy required is dependent upon the position of the ship with respect to shore as well as upon other conditions affecting safety.