The "International Regulations for Preventing Collisions at Sea" were adopted as a convention of the International Maritime Organization on 20 October 1972 and entered into force on 15 July 1977. They were designed to update and replace the Collision Regulations of 1960, particularly with regard to Traffic Separation Schemes (TSS) following the first of these, introduced in the Strait of Dover in 1967. As of June 2013, the convention has been ratified by 155 states representing 98.7% of the tonnage of the world's merchant fleets.