Strait of Istanbul, major accidents and abolishment of left-hand side navigation

Strait of Istanbul is one of the most difficult waterways in the world. It’s curved structure, sharp bends which require 12 major course alterations form a unique marine environment for passing vessels. Currents also form a natural difficulty for navigation, especially at areas at the North of Kandilli point. There are three types of currents prevail in the Strait of Istanbul: the first is the surface currents, which finds it’s dynamics at the difference of sea levels between Sea of Marmara and Black Sea. Due to this difference in levels, which is around 40 centimeters on average and fed by the rivers flowing into Black Sea, waters run down to Sea of Marmara and to outer seas. Second, is the counter currents and eddies inside the bays. Third is the subsurface currents, formed by the difference of salinity between Marmara and Black Sea, starts from 10 meters to 40 deep and in counter direction with the surface currents. To make this currents system more complicated, in the case of strong SW winds when lasted more than 2-3 days, the whole currents system changes when the surface currents reversed by the wind and above-mentioned difference in sea levels exchange positions to the favor of Sea of Marmara.  Due to this unique system of currents, Strait of Istanbul used to have a unique navigational system, too. Starting from ancient times, ships navigating in the Strait of Istanbul used to navigate on the Port side, especially when navigating from Sea of Marmara to Black Sea direction. Thus, ships could get better protection against current. This practice was inked on the paper in 1933 and by the Istanbul Port Regulation through which it became compulsory for ships navigating in the Strait of Istanbul. But as the international regulations on the preventing collision at sea emerged and it appeared that right-hand navigation was established for narrow channels and altering the course to Starboard in the head-on situations has become a rule, the Left-hand side navigation in the Strait of Istanbul started to lead to confusion. There have been three major accidents in the Strait of Istanbul which could be attributed to confusion created by this national rule against the international rule; in 1960, 1966 and 1979, finally Left-hand side navigation in the Strait of Istanbul was abolished in 1982. This article is about these long-term proceedings of Left-hand side navigation in the Strait of Istanbul, concentrating on and analysing three major accidents.